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Old 11-19-2004, 04:55 PM   #1
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Swirl port heads and why they need to go

All 87-95 truck and car TBI v8 engines got swirl port heads. Same with the Sy/Ty turbo v6 (LB4 heads). These heads are TERRIBLE for flow, the intake port size is huge at 185cc but they flow less than any other production chevy head! The only good thing about these heads is that the combustion chamber isn't AS pathetic. I can think of at least 4 other heads that have worse chambers but that doesn't make up for the fact that your cylinders are barely filling with air and fuel!
This post should be a sticky where people ONLY post information regarding these heads. No posts about "they aren't that bad" because face it, they are.
The LB4 heads were tested to flow only 165/119 (in/ex) @ .500 lift. To put that into perspective I've attached a graph showing you a couple other heads.
Graph has been updated to show that with porting the heads will flow something more respectable. The intake still falls way short but the exhaust is where the sbc has always needed work. Dyno Don has done his homework and made these heads work rather well. He polished the exhaust port and touched up the intake, look at the flow and his 35+hp gain. Good job Don.
Click the image to open in full size.

Last edited by JPrevost; 04-26-2005 at 07:35 PM.
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Old 11-19-2004, 05:12 PM   #2
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Here's a picture that I grabbed from http://customclassictrucks.com/techa.../0405cct_head/
Their website is full of interesting articles.
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Old 11-22-2004, 01:36 PM   #3
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I agree with your comments on the chamber shape; I compared a set of iron LT1 heads to a set of LO3 heads and found the same thing.

Dyno Don should have them (the flow numbers you seek); he may have even posted them before on TGO. I know he flow tested a set of stock LO5 swirl port heads, then did some very mild porting on them, and then retested. IMS he also chassis dyno'd the car and ran it on the track.

To paraphrase his results, the stock heads didn't flow well (as expected), but most stock (Gen 1) GM passenger car heads (that preceded the LT1) don't flow all that well anyway. DD got much better numbers after the porting job, so IMO they aren't as junky as most people would believe.... if you are willing to spend time porting them.

IIRC DD didn't try to hog away the ramp (which should be left mostly in place to retain the swirl); my guess is that he removed the part of the ramp that's visible thru the intake port, which helps airflow on the outside wall area -- where most of the airflow is anyway, AND he probably smoothed the ramp end to allow some intake flow along the inside port wall. If you look in Vizard's Chevy head porting book, he outlines the areas that need the most help on Gen I heads, and those guidelines apply to LO3/LO5 heads even with the swirl ports.

I don't recall what he did on the exhaust side.

I know the intake entry geometry is lousy (big rectangle area that's immediately obstructed by the pushrod indent) so that's one of the Gen I engine problems that was fixed in the Gen II engines (LT1, L31) by revising the head casting. Raising the port on the Gen II heads also helped maintain the port volume and allow a better transition from manifold-to-head.

Anyway, search for Dyno Don's post. It has the flow numbers you want. HTH.

EDIT:

http://www.thirdgen.org/techbb2/show...hreadid=177465

http://www.thirdgen.org/techbb2/show...&highlight=LO5

Last edited by kdrolt; 11-22-2004 at 01:45 PM.
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Old 11-22-2004, 02:45 PM   #4
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I apologize if it's my fault or my computer isn't displaying that graph correctly, but I can't see the flow lines on the graph for the swirl port heads. I see the end-points at .500, but nothing below that lift.

Also, I am surprised at the low exhaust flow of the swirl port heads. I just happen to have a set sitting disassembled on my bench right now. The intake flow is obviously crippled by the "swirl vane" but the exhaust looks pretty much like most SBC exhaust port of that era, to my untrained eye. I wouldn't have imagined that it would flow 50 CFM less than a similar vintage L-98 head.

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Old 11-22-2004, 03:39 PM   #5
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Re: Swirl port heads and why they need to go

Quote:
Originally posted by JPrevost

This post should be a sticky where people ONLY post information regarding these heads. No posts about "they aren't that bad" because face it, they are.
Can do JP.

I will leave it up for now and when the discussion runs it scourse I will add it to our technical discussions section.
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Old 11-23-2004, 05:26 PM   #6
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By the time you pay for a valve job, new valves springs, seals, port work and have every thing set up you will a few dollars shy of some new vortec or world s/r torquer heads. If you want to reuse them they will make good light boat anchor.
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Old 12-02-2004, 06:49 PM   #7
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kdrolt and I have had some lengthy PMs going on so I've updated graph to show Dyno Don's work.
I'll tell you now that I still consider them junk, but only for 99% of the world. If you are one of the few that do your homework the heads might not be complete junk. You MIGHT get some impressive results if you do it right .
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Old 12-03-2004, 10:46 AM   #8
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You head guys are misdirecting the average engine builder by dismissing the swirl jobs entirely. I've got three small blocks running them and for use under 5000 RPM they seem like they would be more efficient than some stock heads. I drive my cars on the street, they never see 5000 RPMs. So what matter is flow up there? If you don't own any heads, I agree, don't buy swirlys,, If you have a set and they are not cracked, put your money in pistons and cams..If you haven't won a race by the time you get to maximum head flow---
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Old 12-03-2004, 02:01 PM   #9
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Quote:
Originally posted by BirdofFireBOB
You head guys are misdirecting the average engine builder by dismissing the swirl jobs entirely. I've got three small blocks running them and for use under 5000 RPM they seem like they would be more efficient than some stock heads. I drive my cars on the street, they never see 5000 RPMs. So what matter is flow up there? If you don't own any heads, I agree, don't buy swirlys,, If you have a set and they are not cracked, put your money in pistons and cams..If you haven't won a race by the time you get to maximum head flow---
Thanks for your opinion but are your engines all in f-body's? The reason I ask is because for an owner of an f-body, performance is always wanted. Street engines, bah, over-rated. Even my dad can't stand his swirl port suburban. Driving around at more than half throttle ALL the time puts his foot to sleep . Our old suburban had the GM goodwrench motor (~40 more hp) and it was a great combination. We didn't have to drive with so much throttle and the gas milage was better (averaged 15mpg, new one is 12mpg).
If you want a motor that can hang with any of the new cars you can't be focusing on everything below 5000rpm. For the average engine builder I still think it's necessary to find a better set of heads and just save up for them. Putting money into pistons is a waste at this power level, the cam of choice is a used Lt1 roller that runs for about $30. Obviously I'm a gear-head, if you don't do ANY form of racing and don't care how slow or fast your car is then by all means, keep the swirl port heads. They're definatly cheaper but don't invest in pistons, just replace it with cast flat-tops and call it "a light weight rotatin assembly"
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Old 01-17-2005, 11:11 PM   #10
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Quote:
Originally posted by kdrolt
I agree with your comments on the chamber shape; I compared a set of iron LT1 heads to a set of LO3 heads and found the same thing.

Dyno Don should have them (the flow numbers you seek); he may have even posted them before on TGO. I know he flow tested a set of stock LO5 swirl port heads, then did some very mild porting on them, and then retested. IMS he also chassis dyno'd the car and ran it on the track.

To paraphrase his results, the stock heads didn't flow well (as expected), but most stock (Gen 1) GM passenger car heads (that preceded the LT1) don't flow all that well anyway. DD got much better numbers after the porting job, so IMO they aren't as junky as most people would believe.... if you are willing to spend time porting them.

IIRC DD didn't try to hog away the ramp (which should be left mostly in place to retain the swirl); my guess is that he removed the part of the ramp that's visible thru the intake port, which helps airflow on the outside wall area -- where most of the airflow is anyway, AND he probably smoothed the ramp end to allow some intake flow along the inside port wall. If you look in Vizard's Chevy head porting book, he outlines the areas that need the most help on Gen I heads, and those guidelines apply to LO3/LO5 heads even with the swirl ports.

I don't recall what he did on the exhaust side.

I know the intake entry geometry is lousy (big rectangle area that's immediately obstructed by the pushrod indent) so that's one of the Gen I engine problems that was fixed in the Gen II engines (LT1, L31) by revising the head casting. Raising the port on the Gen II heads also helped maintain the port volume and allow a better transition from manifold-to-head.

Anyway, search for Dyno Don's post. It has the flow numbers you want. HTH.

EDIT:

http://www.thirdgen.org/techbb2/show...hreadid=177465

http://www.thirdgen.org/techbb2/show...&highlight=LO5
Tried to post picture...I'll try again.

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Old 01-18-2005, 11:48 PM   #11
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Swirl port is bad, but when I ran them I thought the off idle tourque was pretty good. Other than that they suck. Just imagine what the airflow is doing through that intake port a 6000rpm, the swirls gotta be gone.
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Old 01-19-2005, 09:26 AM   #12
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Use compressed air to blow air down the ports after spraying water into them. The only thing the swirl port could be good for is atomizing the air/fuel at idle and low engine speeds.

A ported swirl port is only going to flow about what a 305 HO head flows. You can make a 305 HO head flow almost as good as vortecs on the intake and better on the exhaust.
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Old 01-19-2005, 11:58 AM   #13
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Quote:
Originally posted by Fast355
Use compressed air to blow air down the ports after spraying water into them. The only thing the swirl port could be good for is atomizing the air/fuel at idle and low engine speeds.
The swirl has nothing to do with "atomizing", and has everything to do with (a) increasing the combustion flame speed and (b) improving the combustion flame distribution in the cylinder. Both help emissions and both reduce the need for spark advance.

The books by J.B. Heywood or by R. Stone explain what the swirl ramps are for. There are (or were) very good reasons for it at the time they were designed (mid 1980s). The fact is that head designers got better since those swirl port designs were made, so the swirl plus squish plus good airflow are all still in place even in more recent heads like the LS1.

The info is probably in C.F. Taylor's book too (because everything else is, if you look hard enough).
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Old 01-19-2005, 02:29 PM   #14
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Swirl is over-rated for performance engines. Anybody that thinks swirl is important to induce in a sbc head has to look at the natural location of the intake port angle and location in the bore. There is plenty of swirl happening weather it's induced before or after the valve. The other reason I think it's a poor choice is the use of natural tumble. Tumble being the air flow tripping over itself which is also natural in a standard SBC. What is most important, and the vortec/Lt4 designs prove this, is the swirl (and tumble) induced by the combustion chamber design! And what's even more influential than that is the quenching swirl produced by during compressiong. On a low compressiong motor with a huge old chamber and poor quench I could see the swirl port helping a tad at low engine speeds where the in/ex port volumes aren't causing too much seperation like they do at high RPMs.
So for me, and obviously the rest of the world, swirl ports aren't all that great of a design on anything trying to make horsepower.
One more thing, about porting heads vs stock, it's kind of a mute point. I wouldn't compare a standard BBC head to a ported version, that's just not natural. So if you're going to talk about porting you might as well compare the heads as both ported. Example; portec vortec heads make ported swirl ports look like again rather shabby on both ends.
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Old 01-19-2005, 08:33 PM   #15
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Picture of mine after

Hope this works this time
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Old 04-19-2005, 04:18 PM   #16
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I am not an idiot...yet I need a little clarification on one thing please. Swirl port heads? I know the 305 TBI heads suck, but why the 350? The valves are a bit bigger and they put the same heads on the 350 TPI, don't they???
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Old 04-19-2005, 06:08 PM   #17
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Quote:
Originally posted by Charman234581
I am not an idiot...yet I need a little clarification on one thing please. Swirl port heads? I know the 305 TBI heads suck, but why the 350? The valves are a bit bigger and they put the same heads on the 350 TPI, don't they???
The TPI heads (both 350 and 305) were much different in design. They were a different casting all together with different features.
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Old 04-21-2005, 02:05 PM   #18
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the TPI heads dont have the swirls in them... go figure, they were higher horsepower motors... hum... i completely agree here as i OWN an 350 w/ swirl ports from a caprice... even with the hyd/roller cam setup, this motor has torque, but loses its a$$ in top end... im going to garage port a set of the 87+ TPI 350 heads, known around the boards as 083's... with a decent port job, the flow numbers are equal to, if not better than vortec heads just looking at the picture above makes you wonder wtf gm was thinking putting heads like that on a performance named car like a camaro or firebird... it looks like a speedbump in your heads... and that seems to be just what it is... a speedbump, cuz all these heads will ever do is slow you down...
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Old 04-21-2005, 08:37 PM   #19
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After studying the true facts and my results from mildly porting a set, swirl ports aren't as bad as people say they are. I ran a 15.8 into a 20 mph headwind in a fullsize van with 3.08 gears.

The caprice 350 TBI cam is the same as the one in a 350 TBI unless it is a 9c1 then it has the TPI 305 peanut cam. Stab a LT1 cam in there along with the proper chip, exhaust and you will be suprised.
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Old 04-26-2005, 05:57 PM   #20
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I just wanted to add some links to this thread as well as some flow data that Fast355 provided to me.

187 LO3 stock head flow data

I've got some data from some stock 187s. It was collected at 28 in/h20 pressure drop.

lift_in-----I-------E
.050-----35-----27
.100-----65-----54
.200-----90----113
.300----135----120
.400----158----133
.500----165----140



305 vortec head discussion

Garage ported 193's

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Old 12-10-2005, 09:31 PM   #21
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Just thought I would throw some more info out! My information comes from the August 2002 Hot Rod Magazine 300 HP 3/4 350 article. Basically they took a TBI 4.3, bored it .060, ported the heads (208 CFM intake, 190 CFM Exhaust with 2.02 & 1.60 valves vs. Vortecs 239 CFM intake, 162 CFM exhaust), and stuck a moderate roller cam, a carb and edelbrock intake on it and made 301 HP out of 270 cubic inches with Swirl Ports. They built the engine at 9:1 compression to handle a supercharger or nitrous as well. Knowing that the typical power gain from 1 point of compression is roughly 8%, here is what I figure a 10:1 355 to be. Note they took their block to .060" but I did the more commom .030" over 350.

301/270x355x1.08=427 HP
317/270x355x1.08=450 ft/lbs

That more or less beats the Car Craft battle of the Titans 350 that used Vortec heads, a MUCH larger hydraulic non roller cam, better intake(Air Gap vs. Performer 4.3), better headers, and 10.4:1 compression. The cam that Hot Rod used in their V6 is much more streetable than the one from the Car Craft Build. It specs out at 224/224 @ .050, .525" lift, and 110* lobe-seperation angle. The Car Craft build was 244/252 @.050, .516/.525 lift, 106* lobe-seperation angle. The 4.3 cam is much milder than the Titan which means more low-speed torque, a smoother lower idle, and better fuel mileage along with better low-speed response.

Here is the dyno chart reworked to the 355 and the Titan 350

----------------355--------------------Titan 355
RPM---------HP-------TQ-----------HP--------TQ
3,500------275------415----------275------413
3,600------284------415----------285------415
3,700------298------422----------296------420
3,800------307------425----------309------427
3,900------320------430----------322------434
4,000------329------433----------334------439
4,100------343------439----------346------443
4,200------355------444----------357------446
4,300------366------447----------366------447
4,400------376------450 ---------375------447
4,500------382------447----------382------445
4,600------390------446----------388------442
4,700------396------443----------393------440
4,800------405------443----------398------496
4,900------410------441----------402------431
5,000------414------436----------407------427
5,100------416------429----------411------423
5,200------421------425----------416------420
5,300------422------418----------421------417
5,400------422------411----------424------412
5,500------428------409----------426------407
5,600------428------401----------427------400
5,700------427------394----------426------393
5,800------425------385----------427------387
5,900------421------375
6,000------416------364
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Old 12-10-2005, 11:10 PM   #22
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Fast, let me be the guy to put you down again . Aren't I a killjoy? Going from about 8-9 compression is about 7% gain, 9-10 is about 5.5%, 10-11 is less than 4% and the gains diminish.
Secondly, adding the rotating mass of 2 more cylinders isn't free HP. It takes a lot less hp to turn 6 cylinders than it does 8 and that is why the inline 4 bangers can make some decent hp... not much lost to friction. So you can't just add the hp, it doesn't work like that, I wish it did, then those huge displacement v8's would be getting great gas mileage , same as the smaller lighter engines.
And lastly, what's the deal with comparing ported heads to stockers? Seems kind of apples to oranges. Compare the portec vorted tests to the unported swirls . I mean really now, they're both stock GM castings. Nobody would be suprised if the underdog wins when it's given all the unfair advantages... that's like giving David a cannon and Goliath a target. Hmm, I wonder who's going to win .
If you want, I can use the same math that you do and come up with some amazingly impossible engines. The easiest way to explain my point of the cylinder count/displacement not just "adding" free hp is like this; The imports have been shooting for 100hp/liter and the engines that are doing this all are small, not large! Motorcycle engines 0.6L making over 110hp n/a. So if they made a 5.7L n/a engine it would make over 1000hp. Nope, it would a bunch less because having to stop the extra weight of the rotating assembly takes a lot of energy. Please don't take this personal.
I'm really impressed with the exhaust flow on those swirl ports after porting. I always knew they were good on the exhaust and crappy on the intake. Hence my reasoning to install a single pattern cam instead of the dual pattern.
Oh yeah, and you compared engines with completely different cams!!! What the heck are we comparing here because I see a lot of variables which = a bad test to come to any conclusions. I tried explaining this to kdrolt. If you want to make a point, do it with the least amount of variables. Example; take an engine, dyno it, make 1 change, dyno it, compare the results and you'll have some good data. Making lots of changes like going up 1 full point of compression and changing the heads, then cam, then intake, then 2 more cyilnders, then boring it out, then porting the heads means I can't see WHAT is doing what. Ok, I'm done.

Last edited by JPrevost; 12-10-2005 at 11:14 PM.
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Old 12-10-2005, 11:38 PM   #23
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Quote:
Originally posted by JPrevost
Fast, let me be the guy to put you down again . Aren't I a killjoy? Going from about 8-9 compression is about 7% gain, 9-10 is about 5.5%, 10-11 is less than 4% and the gains diminish.
Secondly, adding the rotating mass of 2 more cylinders isn't free HP. It takes a lot less hp to turn 6 cylinders than it does 8 and that is why the inline 4 bangers can make some decent hp... not much lost to friction. So you can't just add the hp, it doesn't work like that, I wish it did, then those huge displacement v8's would be getting great gas mileage , same as the smaller lighter engines.

If you want, I can use the same math that you do and come up with some amazingly impossible engines. The easiest way to explain my point of the cylinder count/displacement not just "adding" free hp is like this; The imports have been shooting for 100hp/liter and the engines that are doing this all are small, not large! Motorcycle engines 0.6L making over 110hp n/a. So if they made a 5.7L n/a engine it would make over 1000hp. Nope, it would a bunch less because having to stop the extra weight of the rotating assembly takes a lot of energy. Please don't take this personal.
I was just going off a general rule to make a theory. Maybe I shouldn't have come across that this is fact, it's not.

It is however my intent for the swirl port headed 350 that I am building currently. I want to dyno it on an engine dyno, but don't want to have to drive to Oklahoma to do it! My intent is to run it with the ported swirl ports, swap to ported vortecs, then retest. The intakes will both be edelbrock performer RPMs. Everything else will be identical. Timing and fuel mixture optimized for each combination. Basically the best pull.

Not trying to bump heads too hard, but there is only one potential flaw that I see in your Free HP theory. You are working in the same family of engine. Not an imaginary comparison between a motorcycle, a Honda, and a Chevy. The 4.3 is going to take so much HP to overcome the rings, bearings, weight, etc. Each ring, rod, journal, cam lobe, etc is going to generate roughly the same friction. The 350 is going to have to overcome the same thing plus 2 cylinders. You have 2 more cylinders pulling the load, see the problem in that sense. Your 4.3 is going to use a certain percentage of its power to run itself. The 350 being designed the same should be the same scenario and probably down to to tenths of a percent. I don't see how a 4.3 takes any less percentage of power to run itself. True that it takes less overall HP to turn itself, but it is almost without a doubt 3/4 of a 350. The ONLY advantage I see that would go to the 4.3 is less total rotating mass, which would increase acceleration, but not necessarily torque and power.

Also take into consideration the Vortec 4.3 generated 190 HP and the 350 Vortec 255 HP. 190/.75=253.33 HP. The 350 made 330 ft/lbs of torque @ 2,800 rpm and the 4.3 made 250 @ 2,800. Take 250/.75=333 ft/lbs. The difference being the 4.3 has a balance shaft and the same throttle body. The balance shaft probably eats about 5 HP and the less restrictive for the engine size throttle body/intake gives a few horses back.

The 4.3 TBI made 155 net FWHP and 230 ft/lbs. Divide that by .75 and you get 206.66. No take the tq and do the same and you get 307 ft/lbs. That is close enough for comparison purposes to the 200 or 210 Hp/ 300 ft/lbs of the 350. Once again you have the same exhaust and throttle body which is less restrictive to the 4.3. Plus I wouldn't doubt that GM advertising or engineering rounded the HP numbers off!

The third example uses the GM 2 bbl-229 V6 and the 305. The 229 is exactly 3/4 of a 305 and is the 4.3 predecessor and little brother. The 1980 229 made 110 Net Hp and 175 ft/lbs of torque. That measures out to 146 HP and 233 ft/lbs. That is very close to the 145/235 rating of the 2 bbl-305 during that time period. Keep in mind that they shared carbs, intake design, 601 head design, same carb, same exhaust, same air cleaner, etc.

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Old 12-11-2005, 02:07 PM   #24
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http://www.carcraft.com/techarticles/116_0306_vort/
I think I don't have to say anything else on the subject
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Old 12-11-2005, 02:31 PM   #25
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TBI guys arguing about how/why their stock heads suck?!? Of course they suck, there doesn't need to be a post about that basic stuff...
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Old 12-11-2005, 11:31 PM   #26
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You can port a set of swirl port heads and come out with a resonably flowing head with ok flow at mid lift ranges. That much has been proven.

You can port a set of L69/TPI heads and come out with a bit more flow, like closer to the vortecs.

You can buy a set of vortec heads, enjoy the good mid lift range flow, and a much improved CC. Add a set of flat tops to help the quench if your in the middle of an engine build and you can probably enjoy more swirl then you can shake a stick at.

Port the vortecs and your really cooking. Somewhere I recall seeing something like 260 CFM peak at the intake on a ported set.

Get a set of high $$$ aftermarket heads and you can really get alot of flow.

As with anything, the better the starting product, the better the end result. Its clear why the vortec heads and other heads, like LS1 heads, come out on top. Taller, smoother, straighter intake runners. This gives the air a smoother, straighter shot at the intake valve and doesnt make it go around a sharp turn or go around in loops, which results in less turbulence and less pressure loss, which equates to more horsepower. Its really that simple IMO.
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Old 12-12-2005, 08:21 AM   #27
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Quote:
Originally posted by JPrevost
...Going from about 8-9 compression is about 7% gain, 9-10 is about 5.5%, 10-11 is less than 4% and the gains diminish.


Agreed. The gain wouldn't be 8%.

Quote:
Secondly, adding the rotating mass of 2 more cylinders isn't free HP. It takes a lot less hp to turn 6 cylinders than it does 8 and that is why the inline 4 bangers can make some decent hp... not much lost to friction.


Since the engines designs are fundamentally the same (gen 1 type design), then the motored friction increase on the v8 will be proportional and higher than on the v6. So scaling from the v6 to the v8 is reasonable.

The frictional power lost by the balance shaft would be difficult to "remove" without a good engineering model and/or measured data to validate the analysis. So it might be better to ignore the fact that the v6 has the shaft at all.

Quote:
So you can't just add the hp, it doesn't work like that, ..


Actually it does work like that. Scaling from the v6 to the v8 is reasonable in this example.

Quote:
And lastly, what's the deal with comparing ported heads to stockers? Seems kind of apples to oranges.


Agreed. But the Vortecs also have nearly 10 years of development advantage that the SP & TPI heads didn't have, and you already know that the Vortecs flow well in stock form -- so the porting SP vs Vortec is a way to make the comparison equitable. If we were comparing LS1 heads vs Vortecs, the same logic would apply: ported Vortecs vs Gen 3 heads.

Then there is the inevitable cost question. Ported stock heads, either TPI type or SP type are a budget way of equalling Vortec performance as proven by many people here. dimented24x7 pretty much summarized that already.

Quote:

....

If you want, I can use the same math that you do and come up with some amazingly impossible engines. The easiest way to explain my point of the cylinder count/displacement not just "adding" free hp is like this; The imports have been shooting for 100hp/liter and the engines that are doing this all are small, not large! Motorcycle engines 0.6L making over 110hp n/a. So if they made a 5.7L n/a engine it would make over 1000hp. Nope, it would a bunch less because having to stop the extra weight of the rotating assembly takes a lot of energy.


It would get close to 1000 hp, but there would be difficulty in layout, cooling, and torsional modes of the crank to deal with so it's not that simple because 0.6 liters is a LONG WAY from 5.7.

And it's an even more of an apples v. oranges example than a 4.3 to 5.7 comparison. Those high-revving 4 cylinder engines don't have the layout that a sbc gen 1 v6 or v8 has. Because they were designed as high rev engines, they have needle bearings in places that the GM engine doesn't, and they used lighter mass (and more expensive) engine components because they were designed for a different purpose. So the motored frictional power loss by those engines is different because of that. If you scaled one of those engines to a larger displacement, then the engine output would be valid for that type of engine only. IOW if you scaled the 4 cyl motorcycle engine to 5.7 liters, it would not be a valid comparison to make with a gen 1, or gen 2 or a (non racing) gen 3 sbc engine.

The GM sbc v6 to v8 comparison is a valid one; they have more similarities than they have differences.

Quote:


.... What the heck are we comparing here because I see a lot of variables which = a bad test to come to any conclusions. I tried explaining this to kdrolt. If you want to make a point, do it with the least amount of variables.


I understand how that works Jonathan. I also understand that I don't provide nor control the money that people on TGO spend on their projects.... so I can't easily perform the comparison(s) that you demand. So I learned to make due with the info provided, and work with it rather than complain about the excessive variables. You often have to do that in engineering.

Quote:
Example; take an engine, dyno it, make 1 change, dyno it, compare the results and you'll have some good data.
Making lots of changes like going up 1 full point of compression and changing the heads, then cam, then intake, then 2 more cyilnders, then boring it out, then porting the heads means I can't see WHAT is doing what.
With zero knowledge or understanding of an engine, and the underlying engineering and physics, you'd be completely right about your example. Many people here on TGO would have a tough time sorting out the comparison because they lack the tools.

OTOH you have education and experience with cars, you have a version of Desktop Dyno, and you probably have a quarter mile sim tool, so it means that you can easily work with your above example (Fast355's comparison) even though there are "too many variables". And you could also, for example, handle a 5300 lb van running mid 15s in the quarter and then extrapolate it's performance if the same engine were installed into your own 3rdgen.

Fast355: what is the status of your brother's truck (he is using ported SP heads, correct?

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Old 12-12-2005, 09:05 AM   #28
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Quote:
Originally posted by kdrolt
Fast355: what is the status of your brother's truck (he is using ported SP heads, correct? [/b]
Well the 1995 Tahoe is running right at 15.0 @ 95 MPH in the 1/4 with a 2.4 second 60' time. It was a GM caprice crate engine with next to no miles on it. That is with my originol ported swirl ports, the crane roller cam I pointed out elsewhere, projection intake, 454 TBI and injectors, the ECM has lots of tuning in both the engine and transmission.
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Old 12-12-2005, 02:49 PM   #29
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You know, for being fundamentally the same, the v8 sure seems to have a heavier valvetrain and rotating assembly. The internal oil passages and bearings added for the extra 2 cylinders is more strain on identical oil pumps. One being worked harder and being a positive displacement pump with straight rotors... those 2 extra cylinders are decreasing it's pumping efficiency. Then there's the spark energy. A v6 at 6000rpm has more time to charge the poor single coil than a v8 at 6000rpm, even 5000rpm!
Then there's the most noticable difference between a v6 and v8 that share the same intake manifold... resonance tuning. Yup, you don't even mention it as a factor but it's huge. The v6's intake valves closing and opening resonate on a completely different frequency than that of the v8. Same goes for exhaust only that isn't nearly as influential.
So what that the vortecs have nearly 10 years. When comparing things either do it at the 1/4 mile or get some data that has very few variables and when there ARE variables you should use them as worse case sencario, THAT is engineering. What you've done in the past is apply general rules of thumbs that were "ok" back in the 60's and 70's. Today there is no excuse for some of the claims you've made. By playing the worse case senario I'm always a winner in the end. My boss and customers think I'm some kind of *** when I end up surpassing all expectations. So for me, I take the worst of the worst. Example; I don't quantify things I can't measure and I take other people's "work" with a grain of salt. There are countless examples of scientists that were so caught up in their work that they fudged the numbers to not look like their work was a complete waste of time. These people are more often than not because that is human nature. I've unfortunatly done it a couple times. Lucky for me I was mentored and learned that you can be just as important to people if not MORE by saying your results were inconclusive because of <fill in the blank> . With that being said, I don't even look at the numbers in Hot Rod magazines. It's too political and they never include enough information to be conclusive. Lucky for me, I read ever article to the end and at least 90% of them say the results are inconclusive which makes me feel better but it's just a way for them to cover up and still spit out the data as fact. Think about it, how many articles really have enough room to say things like, "porting the intake gave us x hp." None. They always do things in huge chunks like porting, cam matching, roller rockers, electric water pump, open exhaust. In the end it's difficult to even compare v8's to each other let alone a v6 to a v8.
If you're going to compare things and say the heads aren't crap then do a test that involves ONLY THE DAMN HEADS being changed. If the compression ratio is off by a little, leave it, just do the test back to back where both setups have the same components. Here's a story that will explain my sceptisism of posting "edjucated" guesses on hp numbers; a friend of mine with his 4.6L 2002 GT went to the track and ran a 14.02 with nitto's. He then went back in 30 degree cooler weather and after they prepped the track, ran a 13.88 . Okay, great, typical gains? Yes and no. Sure that's a time you would expect but guess what, his 60' time was worse and he was trapping slower than before. 3 suposed constants were actually variables; his shifting had improved, he was running higher tire pressure in the rear and low pressure up front with a new alignnment ment for "hot street." Needless to say his front tires were at 30psi and the alignment was off with lots of toe in causing all sorts of mpg issues. So from that we couldn't even decide if he was infact making 3% more horsepower or not. I think he was but what about his shifting, it was a LOT better and the ET was proof. Mr.Drolt, would you care to put some hp numbers in there? One last example; better torque converter as the ONLY mod. All of a sudden the ET's are dropping and the mph is going up... but on the dyno they are making no more peak HP. Go figure right? 1 mod, that's all it took to make the "peak HP" number guessing a complete farse. Bench racing is one thing, this is a whole nother story. At least with bench racing people say hey, "it should make me faster..." not, that <whatever> will give me another 10hp which will equate to an extra mph and reduce my ET by a 10th... haven't we learned enough from ricers to not even be having this discussion?
My point about the 0.6L engine is that it's impossible to use old rules of thumbs and basic phycis to explain such a complicated beast. Just because the temperature is 30 degrees cooler outside doesn't mean the air entering your combucstion chamber is that temp. Heck, with heat soaking I'd be suprised if the temp at the throttle body was 20degrees difference. I've got proof; Impala SS cold air intake. Sitting in staging lanes, burn-out box, at the line... intake air temps were 141 start, 122 half track, and 88 at the end. What was his peak HP if he trapped 99mph and weighed 4400lbs? Or better yet, what would I run in my car if I had his engine? POINTLESS. Now add dealing with cam/heads/intake/vehicle improvements/envirnmental variables, then adding 2 cyliners to the mess and try and come up with a good approximation.
BTW, I'm not complaining about the excessive variables. I'm complaining that they're being ignored which is misleading younger or less knowledgable readers. Like you implied with the "spend on their projects." the TGO owners these days aren't what they were 10 years ago so I play things down. It's evil to get one's hopes up to later be let down. Human's want to believe the best news they hear, not the worst (unless politics are involved ). So if I said 270hp and you said 300hp then the guy went out and made 287hp he'd feel complacent or disapointed. I'd rather give them worse case and be wrong on the low side than wrong on the high for his sake.
Before I forget, my name is Jon, not Jonathan. So try your seniority in person, not here (it'll work in person, just ask Grumpy).
And lastly, no, you can't extrapolate performance of a 5300lb van running in x part of the country to my own 3rd gen when even I don't know what hp I'm putting down at the wheels, let along at the crank!!!
I'll make one last stink; Fast, how the hell is a Tahoe trappying 95mph with a stock swirl port 350, bolt on intake, cam and tuning when the Caprices aren't even capable of that! Something just doesn't sound right. Is your "1/4" mile pointed south or is it pointed south? wink wink. For those not familiar with my obscure humor, south the second time mentioned is 'downhill'.
You must have some really well ported heads and a large lift cam. Does the Tahoe have gears or no and it's lifted with 32's on all 4 corners? That Hummer commertial just popped into my head. So I have to ask... is your 1/4 mile straight and is he taking a shortcut if it isn't?
No matter the case, excellent work with that Tahoe. I'd be happy just trapping over 90mph Big thumbs up.
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Old 12-12-2005, 09:40 PM   #30
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Jprevost beat me to explaining why you can Scale a 350 down to a 4.3.



And Dimented put it the in Lahmans terms, swirl ports are the bottom of the food chain, unless you have something horrible.....like smog heads
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Old 12-12-2005, 09:58 PM   #31
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Quote:
Originally posted by JPrevost
!!
I'll make one last stink; Fast, how the hell is a Tahoe trappying 95mph with a stock swirl port 350, bolt on intake, cam and tuning when the Caprices aren't even capable of that! Something just doesn't sound right. Is your "1/4" mile pointed south or is it pointed south? wink wink. For those not familiar with my obscure humor, south the second time mentioned is 'downhill'.
You must have some really well ported heads and a large lift cam. Does the Tahoe have gears or no and it's lifted with 32's on all 4 corners? That Hummer commertial just popped into my head. So I have to ask... is your 1/4 mile straight and is he taking a shortcut if it isn't?
No matter the case, excellent work with that Tahoe. I'd be happy just trapping over 90mph Big thumbs up.
The 2WD Tahoe is a stock height, stock diameter tire(much WIDER), with 4.10 gears. The cam is the one below, with my first swirl ports(the ones I have the flow numbers on,+ some more), they have the LT4 springs and retainers on them, and will clear .525" easily. The chambers were deshrouded after they were taken off my 355. The engine started as a GM caprice engine. It has been balanced and all dimensions check, rechecked and brought into spec. The block was decked to give a .040 quench with a .038" nominal head gasket. That alone surely boosted compression somewhat. The heads and projection intake were milled, don't recall the exact dimension, all chambers have been CC'd at 62 CC after deshrouding (maybe +3 cc). It has Thorley Tri-Y headers with Y-pipe, Random Technologies cat, Flowmaster 70 series Big Block muffler (made me get one!). To keep the heavy hydraulic roller lifters from floating (problem on my old 355) a REV kit was used. Shifts are made at 6,300 RPM(computer run 4L60E) and the shifter is left in Drive.
http://www.cranecams.com/?show=brows...tType=camshaft
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Old 12-13-2005, 07:42 AM   #32
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Quote:
Originally posted by JPrevost
You know, for being fundamentally the same, the v8 sure seems to have a heavier valvetrain and rotating assembly.




Same stroke, same bore, same valves, same valvetrain, depending on which v8 (305 or 350 cid) is compared to which v6 (200, 229, or 262 cid). The important dimensions of the blocks (bore-to-bore spacing, deck height) are the same. The only significant dimension the v8s have that's larger are the ones having to do with the extra pair of cylinders. The v6 more than resembles the v8, because the v6 was developed from the v8.

Here's a web summary on the 4.3:
http://engine.firebirdv6.com/V690.html

GM prints their own summary in the form of a chapter on 90-deg v6 engines, as found here:
24502488 Chevrolet Power, pp148-165 (7th edition):
http://www.gmgoodwrench.com/perfpart...279&section=pp

Doug Anderson has the definitive article on the 4.3 especially in comparing the original version from 1985 to the most recent:
http://www.babcox.com/editorial/ar/ar40047.htm

His article begins with:
Back in the late 1970s when everyone was worried about the "gas crunch," Chevy needed some smaller engines in a hurry, so it created a new family of junior-sized V6s by chopping two cylinders off its existing V8s. This enabled GM to shorten the development process dramatically because it was able to adapt a proven design. But it also allowed it to share a lot of the existing tooling from the V8 production lines so the engines could be on the road sooner

So despite the gradual changes in the 4.3 design over the years, it's still a sbc v8 that's missing 2 cylinders.

Quote:
The internal oil passages and bearings added for the extra 2 cylinders is more strain on identical oil pumps. One being worked harder and being a positive displacement pump with straight rotors... those 2 extra cylinders are decreasing it's pumping efficiency.


"Are decreasing it's pumping efficiency...." huh?

The extra two cylinders, and the extra lube needed increases the load presented to the pump but it doesn't change the efficiency of the pump at all.

And the reason why the pump is the same? Because the v6 was designed from the v8; the pump was more than adequate for the oiling needs of the v8 so they used the same one for the v6... so no new pump needed to be tooled/designed.

Quote:
Then there's the spark energy. A v6 at 6000rpm has more time to charge the poor single coil than a v8 at 6000rpm, even 5000rpm!


True -- but this is an irrelevant point and (failed) distraction in the discussion. Why? Because the v8 parts could be used on the v6 for that reason, so no new part was needed. As far as 6k rpm is concerned, the stock engine wasn't designed/built/sold to go there.

As I said previously, the engines are fundamentally the same. The components within each are also the same:

Quote:
... These items include valvetrain parts (valves, springs, rocker arms, pushrods, timing sets, and lifters); camshaft and crankshaft main bearings,; piston assemblies (pistons, wrist pins, and rings); lubrication systems (oil pumps, pickups, and drives); and external accesnories (front covers, torsional dampers, flywheels, and water pumps). Ths commonality of design means that many heavy-duty V8 parts can be used without modification, or adapted to the V6/90 Chevrolet.
from p. 149 of Chevy Power.

So Fast355's extrapolation of v8 output from a v6 is valid because the engines are, in Chevy's own words, fundamentally the same.

Your arguments, thus far, are specious. And your claims have no merit.

Quote:
Then there's the most noticable difference between a v6 and v8 that share the same intake manifold... resonance tuning. Yup, you don't even mention it as a factor but it's huge. The v6's intake valves closing and opening resonate on a completely different frequency than that of the v8.




This is really funny now, you attempting to lecture me on acoustics. Mathematically they might resonate at different frequencies (or rpms) but the difference would be an unimportant distinction because the two engine both have dual-planes with runner lengths that are similar. And if the runner lengths were different, it would be possible (if GM cared) to make the v6 and v8 resonate at exactly the same frequency (or rpm) by altering the plenum dimension(s).

You're grasping at straws.

Quote:
....... I'm always a winner in the end.


I couldn't agree more.

Quote:
....Example; I don't quantify things I can't measure and I take other people's "work" with a grain of salt. There are countless examples of scientists that were so caught up in their work that they fudged the numbers to not look like their work was a complete waste of time.


Hummm.

I haven't provided any of my own data into the SP head argument (this thread) so I can't be accused of being biased to my own work.

Should I distrust the work and posts of the 3rdgen people that have posted flow data, dyno data, and track data? The people that provided the data in this thread seemed to be very honest & forthcoming in what they posted, and the rest of their posts sound legit --- so I don't discard them. But I do look for trends in what they report, which is why I concluded that there is very little difference in the TPI heads (081, 083 iron casting for 305 and 350 respectively) vs the swirl port castings (187, 193) for the same engines.

The list of those people (with real data: head flow, dyno results, track data) is growing and yet there still hasn't been any single piece of data to support the title of this thread. There has been ample evidence that the opposite is true -- the SP heads are really no different than TPI type heads in terms of flow and power potential. They aren't high performance heads, and neither are the TPI heads. Both can be ported for excellent gains.

Quote:
....Think about it, how many articles really have enough room to say things like, "porting the intake gave us x hp." None. They always do things in huge chunks like porting, cam matching, roller rockers, electric water pump, open exhaust.


I know. They work hard to make their advertisers look good while still trying to be somewhat honest to the readers. The advertising revenue pays much of the cost of the magazine production, so they're not likely to cast stones. But that also means that their performance claims are an upper bound on what everyone else might attain. IOW you won't obtain 301 fwhp in a 270 v6 build, as HRM did, unless you do exactly the same things they did (which means elec water pump, no air filter, and a velocity stack atop the test engine). I know how to deal with that, as do many informed readers, so the articles are still useful.

Quote:
In the end it's difficult to even compare v8's to each other let alone a v6 to a v8.


For you perhaps.

Quote:
... Here's a story that will explain my sceptisism of posting "edjucated" guesses on hp numbers; a friend of mine with his 4.6L 2002 GT went to the track .....


Remember what I said about an upper bound? There are also lower bounds on performance, and they're usually caused by the thing your don't expect. If your friend's car fails to perform, then there is always a reason for it. It could be driver error, it could be a weak component that needs replacing (ignition, fuel pump), poor weather, or some combination of the above. So if your friend's car runs extremely well, it's because everything was working properly (car, driver, engine, weather)... and the car traps what it ought to.

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Before I forget, my name is Jon, not Jonathan. So try your seniority in person, not here (it'll work in person, just ask Grumpy).


Sorry. I thought you were the same guy that wrote this a few years ago here on the Save the Fbody page:

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GM needs to learn how to market a legend. No ads is a way of slowely killing a car. I actually couldn't care now that GM has totally lost my support. They are loosing trust and that is why they are getting rid of their best followers. I don't know ONE f-body owner that owns a ford as the "other" car.
Jonathan Prevost <jprevost@crosswinds.net>
Columbus, Ohio USA - Friday, May 18, 2001 at 03:44:02 (EDT)
Quote:
And lastly, no, you can't extrapolate performance of a 5300lb van running in x part of the country to my own 3rd gen when even I don't know what hp I'm putting down at the wheels, let along at the crank!!!


Jon, you should be able to estimate both fwhp and rwhp in your car... if you really wanted to. You choose not to, which is surprising since you once were a Mech Eng student and you must have modeled the performance of the SAE competition car you worked on. If you could do it for that car, what's stopping you on your 3rdgen, or on Fast355's van?

You can also assess, if you choose to, whether the performance estimate falls closer to the upper or lower bound of what it should run based on track data. Is 13.6 @ 102 (?) mph appropriate for a 350 HO-type engine using L31 heads and a 4L60? Is your front end tired, has it been aligned, was your driving during the run good/poor? You probably know how maintained your car is, so you ought to be able to assess whether your car's performance is good for it's mods and state of tune.

If Fast355 ran 17.2 sec in his modified van, I would say he has a problem somewhere because even in that van the timeslip would be excessively slow. But he didn't. He ran in the 15s, and that works out to 330+ fwhp, so I'd say he was darn close to the upper bound for performance for his engine with his mods. That's true for the 312 he has now with 081 heads, and true for the 355 he had previously with the [return to thread content] swirl port 193 heads. IOW he'd be hard-pressed to make it go any faster without changes.... but poor maintenance/weather/traction/driving can surely make it run slower.

Last edited by kdrolt; 12-14-2005 at 08:09 AM.
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Old 12-13-2005, 11:37 PM   #33
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Geez guys. What where we arguing over again? I got lost...

Im sure a 350 could make around 380 - 390 HP with the mods stated for the 262 in the hands of some magazine. Im also sure that HP output for the 262 would fall to around 265 HP by the time it was in a car with transmission, a full length exhaust, accessories, and all the other stuff you usually have to do/have when a motor is in the car.
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Old 12-30-2005, 03:37 PM   #34
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this is all great for the 350, but what about the 305?
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Old 12-30-2005, 04:41 PM   #35
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I just need to know one thing and hopefully this won't start any arguing. Are ported SP L05 heads better than or equal to stock Vortec heads? If they are on par with the vortecs is it cheaper to have someone port the SP or is it cheaper to just buy a set of vortec heads? I'm trying to save money and build a good daily driver with around 325 FW HP.
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Old 01-02-2006, 01:34 AM   #36
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Here is a Dynojet dyno sheet of a 9.5:1 350 with the following cam specs roller, 209/210 in/ex duration at .050, .459/.459 lift in/ex, 115LSA. It has lightly ported 193s on it.
Attached Images
File Type: jpg 7c_3.jpg (49.2 KB, 845 views)
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Old 01-02-2006, 07:56 AM   #37
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Quote:
Originally posted by TierAngst
I just need to know one thing and hopefully this won't start any arguing. Are ported SP L05 heads better than or equal to stock Vortec heads? If they are on par with the vortecs is it cheaper to have someone port the SP or is it cheaper to just buy a set of vortec heads? I'm trying to save money and build a good daily driver with around 325 FW HP.
From the chart at the top of the page with the flow numbers, ported SP still fall way short and really bad at mid lift. Any SP head you have is going to be over 10 years old and probly have over 100k on it. Your probly looking at a complete Valve job, new valves, Springs, valve seals, and then pay for some one to port them, I think a new set of vortec's start to look really good. The price on Vortec intakes has dropped in the last few years too, Not like you where going to keep the stock intake anyway right?
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Old 01-02-2006, 09:18 AM   #38
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Originally posted by 91RedFirebird
From the chart at the top of the page with the flow numbers, ported SP still fall way short and really bad at mid lift. Any SP head you have is going to be over 10 years old and probly have over 100k on it. Your probly looking at a complete Valve job, new valves, Springs, valve seals, and then pay for some one to port them, I think a new set of vortec's start to look really good. The price on Vortec intakes has dropped in the last few years too, Not like you where going to keep the stock intake anyway right?
89k to be exact, but I know what you mean. I was looking at a kit that Scoggin Dickey's sells, let me know what you think. SD8060RAKIT
http://www.sdpc2000.com/catalog/2172...mer-Intake.htm

With a 213/219/112lsa cam running .493/.502 (1.6rockers) lift.
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Old 01-02-2006, 09:28 AM   #39
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I just ran the setup on Desktop Dyno 2003, its showing peak torque of 420 @ 3250rpms and hp of 346 @ 5000 with power taking a serious dive after 5500. Does that seem right? If it turns out to be right I'll be extremely happy.
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Old 05-06-2006, 10:02 AM   #40
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from my expirence, the swirl heads run better, i believe the swirl in the intake above the valve is directing stray air back into the area where the velocity is higher. i use my big camshaft to my advantage there. you guys really like those *peanut* cams dont you.
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Old 12-01-2006, 12:54 PM   #41
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So what your showing is that the best heads are either vortec's or afr's which i see around alot. So if I wanted to buy heads that are worth buying I would buy Vortecs or AFR's? Or are these stock heads? I am looking to purchase a pair of heads later in the winter. Shall I purchase afr's or vortecs then get them ported and polished?

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Old 08-08-2007, 02:47 PM   #42
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Re: Swirl port heads and why they need to go

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Originally Posted by I H8 WWD View Post
So what your showing is that the best heads are either vortec's or afr's which i see around alot. So if I wanted to buy heads that are worth buying I would buy Vortecs or AFR's? Or are these stock heads? I am looking to purchase a pair of heads l8er in the winter. Shall I purchase afr's or vortecs then get them ported and polished?
I think AFR heads are to the tune of 1500.00 or so more expensive than a set of vortec heads just FYI.

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Old 08-08-2007, 03:04 PM   #43
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Re: Swirl port heads and why they need to go

Yes I know the AFR's are more expensive....but they are more common at least to what I have read. I think I will go with the AFR's because of the popularity and success of these heads. Thanks for the info though.
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Old 08-09-2007, 02:29 PM   #44
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Re: Swirl port heads and why they need to go

My brain hurts after reading all that ..... I always thought the swirl ports were only designed for low end torque I didn't realize fuel economy and emmisions were also a part of them.
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Old 08-10-2007, 07:33 PM   #45
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Re: Swirl port heads and why they need to go

emissions and fuel economy are a big part of the design of any post 1972 engine. tha is when the tree huggers and oil companies dug in to take our money and the fun out of the hobby.

i still don't agree(even after all these years) that the heads are the biggest problem choking the LO3 in stock form. for a much lower $ to HP ratio you can grab a stock LT1 cam and some fresh valve springs for what amounts to an even bigger gain that swapping a set of heads.

if your goal is to totally build a 305, yes, you will want to go to better heads. if you are jsut looking to up the performance of your stock or mildly modified LO3 car, you will do a lot more buy installing a mild cam and putting some time into tuning it.
----------
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Yes I know the AFR's are more expensive....but they are more common at least to what I have read. I think I will go with the AFR's because of the popularity and success of these heads. Thanks for the info though.
if you buy AFR's you are jsut paying for a name. there are a variety of much better heads out there for a lot less money. you can even match their flow rates and tumble and swirl with a set of off the shelf edelbrocks for $400 less.

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Old 08-11-2007, 03:28 PM   #46
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Re: Swirl port heads and why they need to go

so what is am emissions legal cylinder head that flows well enough to feed a mild 350 tbi
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Old 08-12-2007, 10:38 AM   #47
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Re: Swirl port heads and why they need to go

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so what is am emissions legal cylinder head that flows well enough to feed a mild 350 tbi

Look at a set of ported stock 193 350 TBI heads. Fast355 has made numerous 400hp engines using those heads. A little port work goes a long way all the while retaining good CR, EGR, and the ability to run 87 octane.
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Old 08-12-2007, 11:23 AM   #48
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Re: Swirl port heads and why they need to go

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Look at a set of ported stock 193 350 TBI heads. Fast355 has made numerous 400hp engines using those heads. A little port work goes a long way all the while retaining good CR, EGR, and the ability to run 87 octane.
I ALWAYS get resistance when I bring that up, but Hot Rod also made the equivalent of a 400 HP engine with their 300 HP 4.3 V6, using guess what, PORTED SWIRL PORTS.


HotRod also used a high mileage 318 short block as one of their Junkyard dog buildups and used some #302 swirl port heads on it as well.
Click the image to open in full size.
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Old 09-03-2007, 12:10 PM   #49
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Re: Swirl port heads and why they need to go

(We should get a picture of beating a dead horse on this thread cuz this topic will never die.)

I have a 350 TBI in my 1993 Caprice. It came with a 305 Peanut cam and and 193's. In stock form its rated at 180hp. I have done as many bolt on's as I could...and still hate it. I have an Edlebrock TBI intake that I wanted to use. I figured...due to money constraints...I would be reusing the the 193's. I wanted to just do the gasket matching and the slight port work that has been discussed a million times on this forum and this thread. I figure I am not going for a drag race engine so...they should work fine.

Dyno Don and Fast have both convinced me that they will work...I mean...if they work...then they work. No need to invest in some top dollar heads. Sure aluminum would be swell but...look at the price....then look at the power guys like Fast have methodically milked out of the 193's. Cost vs. performance. I can get what I need out of them. As long as I don't try a cam that is so stout that it'll fracture the head...I won't have any problems. Even just adding some 1.6 rockers will add some nice lift without having to swap a cam yet....but snce the peanut cam is so small...I just can't see myself keeping that P.O.S. with my Caprice. The cam was designed for a F-Body...how it ever found its way into the 1993 Cappy LTZ...I'll never know.
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Old 09-11-2007, 07:36 PM   #50
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Re: Swirl port heads and why they need to go

Wow, this thread just keeps coming up.

Fast, have you ever done a straight swap over, on ported SP, to something else, without other changes? The thing is, all I hear is a ton of theory talk with numbers that we don't have all the data one. We have extrapolated numbers, numbers from all sorts of combo's, diffrent flow numbers, desktop dyno numbers etc. No direct stock 350 SP heads, to standard heads, etc.

I am going to leave it at this. In my car, I hit the wall at about 220 RWHP with the stock SP heads from the LO3. I changed NOTHING else but the heads, and picked up 30 HP at the wheels. In my book, end of story, at least the 305 heads, in stock form hit a wall. If you are going to buy/build a set of heads, why bother with 350 SP heads, at the price of vortec heads, go that route, they are proven time and time again.
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