is it true 305 heads on a 350 produce better power?

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86 berlinetta
350cui w/.30 over
.526 hilift cam
hooker supercomps
3" duals
edelbrock streetmaster
holley 750 dp
bad asshauler

 

No.

How could heads with 1.84" valves allow more flow than ones with 1.94" valves? And then just look at the port sizes.

305 heads generally have smaller chambers than 350 heads, and so would produce higher static CR on any given motor, which would then produce more power if all else were equal. But all else isn't equal, so it doesn't work that way.

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"So many Mustangs, so little time..."
ICON Motorsports

 

When *fully ported* 1.94 1.6 valves and deshrouded combustion chambers they're
not to shabby for a budget street head.
But!, with 20 lbs of turbo boost and 200 hp
shot of juice.........
http://photos.yahoo.com/russ_q

 

I'd agree with the 1.94", but the 1.60" is stretching it. 1.50's are pretty shrouded as it is.

But, as said, if fully ported, and the chambers opened up to unshroud the valves a little, dished pistons, thick head gasket, you'll raise the compression significantly over a 76cc 350 smog head but keep it pump-gasable, and possibly even improve flow. All together, you'll get an increase.

Makes more sense to get a set of 64cc S/R Torquers and put your grinding time into them. 2.02/1.60 valves, 170cc+ intake ports (after some matching and blending), screw-in rocker studs, more valve lift capability, etc., etc., etc. By the time you "fix" the 305 heads, you'll probably have spent as much money as doing these new 350 heads, which WILL flow better.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. 2-1/2" cat-back, ZZ4 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (ported World 305 heads, Crane PowerMax cam, Hooker 2055 headers, 3" Catco cat & 3" catback w/Flowmaster, restalled TC, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

 

Gotta factor in the sleeper factor there some where...I think
Here is recipe for a budget 350 using 305 Ported heads like the ones i did.

355 350+ .030"
stock deck height
H345np Hypereutetic flat tops .045" deck clearance about the cheapest good piston there is.
felpro .039 gasket

full port 305 heads "416" or "601" castings
1.94 1.60 valves 1.255" k-motion K-700 springs 60CC's chambers
remanufactured cast crank
federal mogul deluxe rebuilt kit
rings bearings and gaskets.
your choice intake carb and distributor
your choice Hyd cam and lifters
This motor has a measured compression ratio of 9.73:1 and runs on 92 octane gas
This motor will make between 325 and 380 hp
depending on options combo.
The aftermarket heads are nice stuff but
worked 305 heads on a budget 350 flat top
can be a real life performer.
I had about $650 Canadian into my heads complete so this is hard to beat.

 

Generally speaking 350 heads flow better due to their larger intake runners. 305 heads are best left on 305s. Valve sizes, although larger valves help some, really don't make as much of a difference in flow as the runner size and cam profile used. The smaller combustion chambers of 305 heads make more compression, but you can drop up to a point off using 350 heads going with thinner head gaskets or using higher compression pistons. Use 350 heads if possible since heads are the biggest airflow limiting factor on a motor.

 

Well the intake runner on 305 heads is actually bigger when yu actually measure it.
I found it to be 167CC's with the stock valve..... most 350heads are 155/157cc's Suprised me too

 

Intake runners on 882 heads are 151cc, 441s are 155cc, 462s are 156cc, L98s (aluminum) are 163cc, Performers are 166cc, 855 Vortec iron heads are 170cc, LT1s are 170cc, WPS/R Torquers are 170cc, LT4s are 195cc. Those are the smallest of the 350 heads. Most 305 heads aren't even that big. LS1s are 204cc and aftermarkets come up to 220cc. You won't find many (if any) flow tests on 305 heads due to the fact they flow poorly. It takes alot of time and money to get the 305 heads to where they flow decent, and that's comparing them to stock 350 flow tests. With similar mods, the 350 heads would flow even better also. A good polish & port job results in 5-10% more flow alone. If you want better flow cheaper and easier, go with 350 heads. Aftermarkets flow best, but you have to pay for them.

 

Yes! But limited . The way this senario has been explained to me by EVERY machinist Ive talked to is: "They work alot better than the larger 350 heads (excluding a few castings), because they increase the compression and if you port them a little they wont restrict anything." ME: What about the valves? Machinist: "We can put larger valves in the heads but unless your running circle track or planning on cranking over 6500 an extended period of time the smaller valves wont hurt much if anything!"

Its amazing because Ive used eight different machine shops "two of which were hardcore circle guys" and they all say use the 305 58cc heads.
SSC

EDIT:
Oh I use 58cc's on my Camaro (355) and my truck (355) work great!

[This message has been edited by SSC (edited November 01, 2001).]

 

I don't know what kind of experience these machine shops you've been to have, but I can tell you for a fact that out of comparably ported/modified/stock 305 heads and 350 heads there is no way a 305 head can touch a 350 head on flow. An engine is just a big air pump, more air equals more power. Call a tech rep at Summit, Jegs, GM, any cylinder head shop or anywhere else that knows what they're talking about and they all agree. More flow is more power. Like I said before, the only difference in these heads are the 305 heads have a smaller combustion chamber and usually run a point or so higher on compression. You can change pistons to build whatever compression ratio you want that way. You can even use a thinner head gasket to get back anywhere from 1/2 to a full point, depending on how thick your stock gasket was. 305 heads can be modified to have decent flow results with major porting and polish work, I won't deny that, but the same work done to 350 heads would make them flow alot better too. You can't really compare 305 heads to 350 heads because they were designed differently for the cylinder sizes. Everything on the 305 heads spells less flow from the stock 1.72 or 1.84 intake valves (depending on year and whether it was HO or not) to the smaller intake ports, to the valve bowls and design. IF you have a choice, go with 350 heads. If not, the 305 heads can be ported and polished to make decent HP also if you spend the time on them and money. Read tech articles in Chevy High Performance, Carcraft, Hot Rod or any other magazine. How many 450HP 305s have you ever seen with stock heads? The volumetric efficiency differences in a 305 and 350 only accounts for a small HP difference (most buildups less than 20HP, almost never over 30HP). The biggest difference between the 305 and 350 motors is the torque created (usually at least 50 FT/LBS, commonly more than that). I'm not saying that you should always use the heads with the biggest valves, port volumes, etc. I'm saying that a stock 350 head outflows a stock 305 head across the board, and will result in better overall performance more economically. Consequently, my family owns a major machine shop and does motor work for all of the locals and most dealers within a 50-75 mile radius. I know every engine builder around my area, and we do alot of drag racing around here. 305 heads simply do not outperform 350 heads, except for better gas mileage.

 

Jag : THe 305 casting's intake port is bigger in volume (167cc) than all but a few 350 heads. Once the valve is replaced with the 1.94", it has as much potental as any of the "smog heads".None of which compare with the old camelback fuelie heads. But then we're not comparing apples and apples. But
even then the 305 castings have a bigger port than these. Grab one and cc it You'll see. For a budget build up or replacement these 305 castings are very viable up to 430 hp.

 

Which 305 castings were cast 167cc? Most I've seen were cast less than 150cc. How are you measuring the internal runners, where are you measuring them from, and how are you calculating the cubic cemtimeters from your measurements? The ccs I listed before were all GM's cast in runners. I grew up rebuilding Chevys with my family's business, and I've never heard of anyone measuring an intake runner before. We always used the GM manuals to get the ccs.

[This message has been edited by jag (edited November 03, 2001).]

 

The GM manuals are not accurate ,you know that...
If you really work on hi perf motors
you'd have cc'd a 305 head or two instead
of taking a number on a piece of paper written by an engineer who has probibily never held a head casting in his hand, as holy grail..
I have 3 sets of "416" castings on hand, all 167 cc intake ports . Like I already said
I measured them and then measured them again after porting.... 167cc stock 176cc ported.
I use a 100cc graguated medical buret It is super accurate and available in any Pharmacy
and a 1cc medical syringe for the last little bit. I stand the head ,intake port face up and level and fill it with water till it is full (NOY over full) I use an old CD and some vasoline to cover and seal the
intake opening and valve guide and valve seat
(prevent minor seeage.) This is acurate to whthin 1/4 cc. More than enough TRY it...

[This message has been edited by F-BIRD'88 (edited November 03, 2001).]

 

Without regard to anything else. If you take a basic 350 (fairly low compression) and toss on a set of the 305 heads -- the compression ratio will mostly like end up right around 9-9.5:1. That will overcome all but the best flowing heads on an 8:1 engine IMO.

 

The "Achilles' Heal" (limit) of the 305 heads is the exhaust port. Bad shape, too big.
Not the intake.... Grab a real 305 head in hand and stick your finger in the intake port on the pushrod wall. feel the void of metal right where the rocker stud comes thru the roof of the port? This is the extra volume.
Was made like this to prevent the heads from cracking. This extra volume of missing metal doesn't contribute to or hinder flow in any real way . This is a dead area as far as flow is concerned. Compare to an early or hi perf 350 head.

[This message has been edited by F-BIRD'88 (edited November 03, 2001).]

 

I like you Import Eater, ya know just how to simplify a simple topic... Have a nice day...

 

Ok, like I said, I'll give you that 305 heads will flow decent if you work on them quite a bit. As for the GM manuals, they are pretty accurate - I worked for Gibbs die casting making these heads for while, and the core sizes we cast around were always the same size or within 2 or 3 cc due to heat changes because of how fast the operators were with the cycle time - the faster you run the smaller the runners. Have you ever seen the flow results from a 305 head anywhere? Why has no magazine ever used 305 heads for a buildup street engine? As for compression gains, going from 64cc to 58 cc is not alot and can be compensated in head gasket thickness in most cases. Compression ratios don't account for as big of a HP increase as you might think. A 350 with 350HP only gains or loses around 10HP and 10FT/LBS with each point of compression. The performance of the head (flow data) is what makes power. The only 305 flow data I've seen was about 20% lower than 350 heads.

 

Jag :Read my posts .I just gave you the flow data
on my heads. I don't know where you have been for the last 20 yrs. but certainly never in a performance machine shop
or a dyno room or a race track. Either circle track or drag. Hot Rod and Popular Hot rodding have done many articles on 305 heads on 350's for budget buildups.
David Vizard has done 2 or three specific articles in the last 10 yrs on 305 heads.
305 heads are very popular on street stockmotors cause its a easy cheap way to boost the compression on a stock 350 (76cc) heads with 58cc heads. a big jump in compression for a few dollars.
Summit Racing (no small place) recently had a budget racing assembled long block
(less intake, carb and distributor) 383cu in
small block chev 14.5:cr with Ported 305 HEADS dynoed at 440HP for a very reasonable
price, in their catalog...

A certain IHRA legal Super stock Monte Carlo from around here (Southern Ontario.) Held the SuperStock record for a while with a 305 with 305 heads, stock port size and valves, in his class...Note: I don't claim to get even close to what he is getting on a flow bench with his *legal* heads. but shows you the potential.

10.91 quarter mile ets
I don't think you have clue what you're talking about.... You cite a fact then say you read it or assumed it. there is no truth or credibility to what you say....
All these 305 heads were cast in house at GM
foundries... like ST.Catharines Ontario and
Tonawanda NY and such....

[This message has been edited by F-BIRD'88 (edited November 03, 2001).]

[This message has been edited by F-BIRD'88 (edited November 03, 2001).]

[This message has been edited by F-BIRD'88 (edited November 05, 2001).]

 

F-BIRD'88, First of all, GM does NOT do all of their work in house and MOST of is contracted out to companies like Gibbs Die Casting, where I worked. We specialized in aluminum heads, and aluminum blocks as well as OWN the pattent for the 32 valve NorthStar complete engine that I WAS THE QUALITY MANAGER over these for 3 years before I went to GE Aircraft Engines for more money. Second of all, I never said you couldn't get decent flow results from 305 heads, I said you had to put alot of work and time in to them to get decent flow results where stock 350 performance heads (like the aluminum L98s or LT1s or Vortecs) had better flow results from the factory and didn't require the time the 305 heads did to get good flow from through extensive porting work, valve changes, etc.. My point was that since most 350 heads flow better stock than 305 heads stock (stock valve sizes, no porting, etc), the 350 heads were a more economical choice when the time was added. You need to compare apples to apples. The compression ratio isn't worth as much as you think, and if you're worried about it using 350 heads go with a .020 gasket instead of a .040 to get back the compression lost, or change pistons if doing a rebuild. As for magazine articles, I have seen a few using 305 heads for 300-400HP buildups. The articles I read were basically Chevy High Performance articles and were only built with 305 heads to see how much power they could put out. Consequently, the 400HP buildup only lasted a couple passes before the heads cracked. You gave me the flow data for your heads? Where? Anyway I wasn't talking about your heads, I don't doubt your heads can make alot of power if you've put the time and money into them. What I was talking about was STOCK 305 flow numbers at different valve lifts. As for where I've been the last 20 years, I have a BA degree in engineering and work for GE Aircraft Engines ($130 billion in annual gross revenues) designing turbine airfoils for use in turbofan, turbo prop and other aviation areas including power plants and ships. I worked at Gibbs Die Casting before that as a machinist doing OEM auto parts finish machining. The only reason I don't work in my family's machine shop is that I make $95k/yr working for GE. We do have a dyno that we test engines on, and I do occasionally operate it for my friends' engines. How many articles have you seen 305 heads used versus 350 heads used? Why do you think the 350 heads are used more often than not? Your 14.5:1 compression 383 will have a followup shortly on the fact it won't last a week before cracking the heads due to the increased temp the compression puts on them. (Aluminum heads dissipate heat better and could handle that compression easily.) I bet you'll find that the heads they used were L98 aluminum heads just like Lingerfelter uses in most of his buildups, just like I have on my SS, just like GM put on the 86-91 Vettes, and just like what used to come on the GM ZZ3. They are 58cc angle plugged 163cc 1.94/1.5 and flow well when ported correctly. I respect your opinion that 305 heads can flow well with alot of work, and I'll give you that. My entire arguement is that similar work on most 350 heads would make them perform even better also, keeping their flow advantage over 305 heads. I'm not trying to **** you off, I'm adding points to the 305 vs. 350 head arguement that you seem to be ignoring, like the fact that 350 heads FLOW MORE AIR when similarly compared to 305 heads. Forget compression, you can deck the block, heads, use thinner head gaskets, different pistons or whatever. Give me some respect here, I work with data like this all day for engines measured in thrust, not HP.

 

many of the circle racers around here run 305 heads and make tons of power and go fast. They seem to know what really works and I believe them because you can see the results. I'm going to use 305 heads and port them myself. They seem really cheap and they work. I don't care to have them flowed or whatever, I just want to go really fast.

 

Just two comments.
One, F-Bird'88, in your first post you referenced the "Sleeper Factor". As far as heads go, what are you talking about? Unless the guy's an expert, he'll never know the difference.

Jag, wy does dealing with engines that deal in thrust not HP require that anyone respect you? Or is that some way of saying "Give me some slack?" If so, it doesnt have the same ring. When did Engineering go to a BA degree, thought it was always a BS (Bachelor of Science) degree, what with all the math needed.

Just a couple of quality, value added, customer driven comments from you local, only-for-you, and always for less,

Clayton

 

Thrust is actually more sensitive than HP. Jet engines run anywhere from 2700 degrees to over 3500 degrees depending on the application (commercial versus military). Different engineering areas may have different degrees, going to school through GE taking their prepaid courses gets you a BA degree. And no, I'm not looking for anyone to "cut me some slack" because I don't need any. A good arguement is healthy and fun as long as it's between educated people that although they may not ever agree, they both understand the other's points. It seems F-bird got a little insulting when confronted with facts versus hearsay from some machinists probably right out of high school with limited engine building experience, or some old foggies with a sixth grade education. I've built quite a few engines, mostly 305s and 350s, and I've always had better results with the 350 heads. I know 350 people that have used 305 heads in their rebuilds (as a matter of fact one of the guys working for my dad does this), and to be quite honest I'm not that impressed. Anyway, the point I was making earlier was that I deal with such crutial air flow tolerances that a turbine airfoil can actually melt down if it flows .00001 cfm over or under the tolerances specified on the B/P, which are usually not very wide. I know that ANY engine makes more power if it flows more air. Obviously a car motor is not going to be as sensitive to airflow data as a jet engine, but HP just like thrust is calculated by the volume, density, charge, temperature, pressure, etc. of air moving through the engine. Generically, if a cylinder head 'A' flows better than cylinder head 'B', then cylinder head 'A' will make more power on the same engine if all other variables are kept the same. The problem is that inexperienced or uneducated engine builders only understand that compression makes more power, which to an extent is true, but on an average motor with 300-400HP going from 9:1 to 10:1 (one point) compression will only yield 10HP and 10FT/LBS on average. Stock 350 heads come in 64cc and 76cc commonly, where 305 heads come mostly in 58cc. Going from a 76cc 350 head running 8.5:1 compression to a 58cc head will result in 10.5:1 compression. That's a little much compression for an iron head and will need timing changes, EGR, a very good cooling system and a good combustion chamber polish job to slow detonation and help keep the heads from cracking. Going from the same (8.5:1) 76cc to a 64cc however will result in 9.7:1 compression which is about ideal for a street application. Every .020" added or removed from the compressed thickness of the head gasket changes the compression by 1/2 point. Another way to control compression is to have the heads milled, removing some of the combustion chamber and raising the compression ratio. (Pistons are the best way to control compression if you're rebuilding.) My point is that there are several ways to raise compression with little time and money involved, so compression is not a good reason to use a poor flowing head. Overall flow data and port volumes should be how you decide what heads you want to use. Has anyone ever seen 305 flowbench data? Here is a link to some 350 data http://www.airflowresearch.com/chptest.html for anyone intrigued. 305 heads and 350 heads run the same price at most machine shops rebuilt, so why use the underdog? The only way I'd use 305 heads on a rebuild is if I didn't have the money to buy heads and already had 305 heads. By the time you spend the money having the heads decked, magnafluxed, ground, cleaned, etc. and then modified with larger valves and invest the time to extensively port and polish the 305 heads, you'll have more money and time into them than 350 heads and have about the same power.

 

F-BIRD'88, we can go on and on with this, I don't expect to get you to change your opinion and don't expect me to change mine. Don't get mad, I'm just giving you a good friendly argument. At least we aren't arguing Ford versus Chevy! Anywho, How much does $650 Canadian equal in US$? I used L98 aluminum 350 heads on one of my 305s I just built, and stock L69 heads on the other. I got the L98s for $200 rebuilt from a buddy (he needed the money), and the 305 heads cost me $250 in parts to rebuild (with new valves, etc.). I did port match intakes and heads on both engines to the Fel-Pro intake gaskets. While my 305 heads seemed to make more power ported than they did stock, they just don't compare to the L98s. My 87 SS Aerocoupe runs 14.8s with the modified heads and performer cam. My 88 with the L98s runs 13.1 at 109. They were both 15 sec cars before any mods were made. The only advantage the 88 has over the 87 besides the L98s is a Performer intake, but it is also handicapped with it's factory 2.25" 'duals' with a high flow cat where the 87 has true duals and 2.5" plumbing. Overall I must say I've been impressed with both of them. Next spring the short block will change in my 88 to a 400 block with a 350 crank for a destroked 377 and some new 2.5" duals. I don't want to change my 87 Aerocoupe much, so it will eventually get a forged assembly with a supercharger.

 

hehe i'm with fbird88 and ssc.
I trust those old guys that been racing for 20 or 30 years and winning before i trust flow numbers.

------------------
1986 Iroc 305 small block chevy getting modded now for speed

 

I'll trust the engineer.
bsa

 

I wouldent trust anybody who though 145 crank HP would suffice in a "sportish" car.

SSC

------------------
85 Camaro, 355/400 "drag car" in moth ***** 13.1@ 101mph on its last season run.
Plans: Possibly add N20 for next season.
82 Firbird, getting a beef injection 355/700r4 3:42 powertrax system.

 

Jag – Quote - My 87 SS Aerocoupe runs 14.80’s with the modified heads and performer cam. End quote-------------------14.80’s -- that’s a little quick, with “port matched” 305 and a cam,, with the stock intake,,, even with “true 2.5 duals”,,, and especially in a Aero,, but I’ll give you that without much grief – IF you did more than just a “port match”.

Jag – Quote - They were both 15 sec. cars before any mods were made. End quote.---------------They were high 15 second cars stock,,, the Areo were the slowest of the Monte Carlo SS,,, but no need to challenge that.

Jag – Quote - My 88 with the L98s runs 13.1 @ 109. The only advantage the 88 has over the 87 besides the L98s is a Performer intake, but it is also handicapped with it’s factory 2.25” “duals” with a high flow cat. End quote -------------------That’s about a total load of crap. Bolting on a set of L98 heads, performer intake,,, and the stock exhaust,, including the cat,,,, is NOT going to reduce your times 1.7 seconds. That’s over 97 horses at the rear wheel. I don’t care if you say the guy had bought the heads from LPE,,, that they were fully CNC ported,, he paid over $2400 for them,, and you got them at a steal of a deal for $200. No way no how.

This internet really ticks me off,, it’s like hanging out listening to the BS artists at the local street racer hang out,, and not being able to shut them up by demanding they put up or shut up.

[This message has been edited by BadSS (edited November 04, 2001).]

 

An Aerocoupe has exactly the same L69, 200r4, and 3.73 gears as a notchback SS. They run pretty much identical times, usually low 15s stock. The Aero runs side by side with the regular SSs, they are the same car except for the rear window. I don't know what the 88 ran before it was modified, so I don't know how much the heads and intake improved it. Chevy High Performance did a similar setup starting with a SS Monte Carlo in 96 (base 180HP 210FT/LBS, L69 305). It started running 15.08 at 92. They added a 203/212 degree .429/.438" 110 degree cam and redynoed it at 200HP and 240FT/LBS. The car ran 14.7 at 93. Then they advanced the timing and added a Performer intake. The engine dynoed at 224HP and 254FT/LBS, and the car ran 14.3 at 96. The next step was adding 305 S/R torquers, changing to a 219/229 degree and .462.482" 110 degree cam, and rejetting the carb. This combo made for 264HP and 272FT/LBS and the car ran 13.4 at 102. The car they used had quite a few miles on it, so the suspension was probably not tip top. This is where I got my idea for my engine in my 88. I used a 214/224 .442/.465" 112 degree cam that would work with my computer and added a set of Flowtech headers to go with the angle plug L98 aluminum heads. The metering rods were changed to the suggestion of some carb guys here that emailed me the idea to try smaller dia ones. They seemed to work well. They also had me use a different spring for the secondaries to help them open faster. I didn't do the carb mods myself, I don't know carbs well so my dad rebuilt it for me. I added the Performer intake and Comp roller rockers (1.5) and used single chamber Thrust mufflers, PFP high flow cat and widened the rear tires and wheels to hold better traction. I also changed to an open element 14x3 air cleaner. I expect to pick up a couple more HP going to 2.5" true duals with no cat. My 87 wasn't modified as much, it doesn't have roller rockers, it has the stock intake and no carb mods, only gasket matched heads & intake and a 204/214 .420/.443 112 degree Edelbrock performer cam and 2.5" dual exhaust. It will have headers soon, and hopefully a supercharger when rebuilt with forged pistons, forged rods, forged crank, Trick Flow heads. You guys are missing my point entirely. Show me just one 500-600HP 350 using 305 heads. 305 heads are ok for lower 300-350HP 350s, but they suck for performance when compared to performance heads, stock, modified or aftermarket (Vortec, LT1/4, Trick Flow, etc). Why do think they don't sell performance 305 heads? They suck! Look, I don't do the circle track thing, but I do frequent the quarter mile dragstrips. I can't say I've known anyone that uses the 305 heads there (to my knowledge). Everyone around here seems to order the $600 Vortecs, LT1s, S/R Torquers or other aftermarket heads. They make more power and you don't have to grind the crap out of them hoping to make up for their pathetic flow numbers, small valves and port sizes. Granted 305 heads will hit peak flow before a 350 head will due to the smaller valves and smaller intake runners, but they will bottleneck to their flow capacity usually around a .400 lift. 350 heads will not respond as quickly because of the larger valves and runners, but will make more power due to higher flow data usually up to .500 or .600 lift. How large are the circle tracks anyway and are they just a circle? (I've heard the term, but we don't have any around here.) If they are short bursts of power, that would explain people wanting to use 305 heads for them. For a daily driver performance 350-500HP street car I'd go with 350 heads (any day of the week and twice on Sunday) that were designed for the desired purpose. Note that all 350 heads were not created equal. Example: 882 castings flow well up to .400 lift, but due to their small intake runners they have excellent torque and response time with 1.94 valves. They are good for 300-350Hp buildups, and comparable to 305 heads with exception of the combustion chamber size. I have seen people mill these down to 60cc for use on 305s and to gain compression on 350s even. Even though they make excellent power for a 300-350 HP buildup, they suck when compared to a 500HP buildup using Vortecs, L98s, or other performance styled 350 heads. My advice to anyone building would be to first plan out your powerband and expected power range. The decide how much money you want to spend. I usually suggest finding a 350 from a Chevy truck and rebuilding the long block with a master kit (pistons, cam, etc) for the power you want to make. Stock 350 heads are generally good for an easy 400-450HP if machined correctly, built properly, and are decent castings. No iron head should be used on anything over 10:1 compression for a street car due to the heat problems. Aluminum heads should be used when higher compression ratios are used. EGR does help somewhat (if used) by reducing temp and will not affect flow. HP is the measurement of how much air moves through the engine, torque is how strong the movement of air is. Torque gives acceleration, HP gives speed. If you want to build a mild 350, use 305 or 350 heads. If you want a 12 sec. screamer go with performance 350 heads or aftermarket. How many circle track racers use aftermarket or performance 350 heads compared to 305 heads? (just out of curiosity I've been assuming you are talking about the 1.84 valved 305 heads not the 1.72s correct?)

[This message has been edited by jag (edited November 04, 2001).]

 

BadSS: Don't be suprised if ya don't get to far with Jag. The credibility gets worse and worse, doesn't it. "Horsepower is the measurement of airflow through and engine"
- Realy now? I hope to *** the college guy
who handed you your "BA" Engineering degree
isn't amoung us here. 'Cause He'd be Chokin'
and laughin'. Horsepower is a measurement of
WORK over time/distance. Did ya catch the Quadra-holy carb he's got on the Monte that his Dad swapped sec metering rods and secondary springs on? It very well may have gone as fast as he says, but he sure had little or nothin' to do with that.
Of course the thing had all kinds of other bolt ons like roller rockers, intake manifold, modified qjet or holley, (not sure which) His Dad probabily reworked those corvette heads and throu in a 400 crank too. {Ok Jag, I'll lay off ya... } But only if we "put this to bed".
Yes, Jag there are other heads! But I stand by what I said to the original poster:
You can throw on a set of 305 heads on a 350
and get some power. Works even better if ya tweek 'em a bit. Most of us have more time than money so that shouldn't be a problem.
Look for around 325 to 380 Flywheel HP on the street, depending on final combination.
There are lots of ways to skin a cat. And this is one. Have a nice day....

 

Actually HP is not a measurement of WORK over time/distance, it is the unit of measurement for the mechanical rate at which work is done, and is a factor of torque. Torque is the force of the rotation, which is controlled by the airflow through the engine. That's why I said HP is the measurement of how much air moves through the engine, it is. My heads and carb were rebuilt by my dad's shop (except for the porting work I did myself), this is true, what does that have to do with anything? He has the only machine shop around where I live, where else would they have been built? Someone's back yard? As for the 400 crank, I wish I did have one. I'd grind down the journals, notch the bottoms of my cylinders and make a 335 stroker with 6" rods! (I'm joking about that, I would prefer a 350, 377, or 400 though to my 305 block) Yes, 'the guy that handed me my degree' would probably be laughing his a@% off if he were here that I was taking the time to explain simple theories such as airflow determining HP to people that can't seem to understand anything but 'bolting on 305 heads to raise compression'. What do you do for a living? How educated are you? I find it interesting that you can't seem to handle an argument without attempting personal insults, despite the fact you won't deny that 305 heads don't flow as well as 350s stock, and that when comparing apples to apples (both heads polished & ported or not) most people building engines go with 350 heads over 305 heads. You should read a few books by John Lingenfelter. It's like he says, "The world's best cam combined with a poor set of heads will produce an engine that's a dog. But bolt on a set of great heads, even with a poor cam, and that engine will still make great power.". Read some of his literature, the man knows his stuff and is an old pro at what he does. He used L98 aluminum heads on most of his 450+HP small block projects until the newer Vortecs and LT heads cam out. I have never seen him use 305 heads, even modified. (Personally, I have no argument that 305 heads can make some power on a mild buildup, but they need alot of work that performance 350 heads generally do not.) It's obvious that we differ in opinion, even most builders will not agree on alot of details. I have quite a few friends into 1/4 mile drags (they got me into it), and people at the strip argue all the time over the best setups. We settle arguements on the strip around here. If you were more local I'd take you down to the dragstrip and we could run'em! I'll start looking for some flow bench data on 305 heads, if you come across any post a link, I'd love to see the numbers.

[This message has been edited by jag (edited November 05, 2001).]

 

Not to take away anything from Linkenfelter
(Talented long time racer, engine builder,
and noted corvette tuner.) whom I'm very aware of. Your statment about more airflow always leading to more horsepower is wrong and way to broad. I'm sorry they misled you in engineering school. Unfortunatly it is much more envolved than this in a piston engine. Here's one of many documented examples of a
a to b test where things didn't quite work out the way you'd claim them to.
Check out Car Craft Sept.2001 pg 76 and 77.
basicly it is a back to back test of the two new E-Tec (vortec style heads) from Edelbrock. One has 170cc ports and flows
233@.500/@28" the other is 200cc's and flows
253@.500 and a max of 259@.700. both heads are otherwise almost identical. Yet in a back to back test, the head with less air flow made the most power. They are two good heads on the same motor with a lowsy camshaft
But by your rule. the one with more airflow should have made more power. Well it didn't.
nor did it make even close as much torque.
The smaller one would spank the bigger one on any dragstrip in this motor, as it did on the dyno on this motor. All thou I don't have an engineering degree like you or pretend to know as much as J.L. I've been to the school of experience for while now and understand the physics of this result. Do you? This is not a hair dryer . And bigger is not always better or faster but usually costs a lot more.
There are lots of other influences that contribute to how much power and torque an
engine will make... like velocity, charge quality, induction and exhaust tuning, Port swirl,and friction, $$$$'s and airflow too. Other wise it wouldn't take much thought to design a motor
for more power, just put every thing big on.
This is why such lowly heads like the 305 heads often can out perform a better flowing head especialy on the street and for a lot less. Of course the L98 heads have more ultimate potential. J.L. and CNC Cylinder heads get about 300cfm out of them. But check the price
lately? Of course all that's irrelevent when ya make $95K a year and got friends that toss
away $1000 cylinder head cores (L98) for $200. No dig intended just the facts.
If you'd like a copy of the article let me know....

 

I think what some people here aren't seeing is that most people who are doing a 350 buildup in a thirdgen are switching from an underpowered 305 and dont have a lot of $$ to spend. Lets face it, a well built engine would cost more than the bluebook on some of our cars, so not everyone is after ultra high performance. Most people are looking for a decent engine that is more powerful than their 305, that is as cheap and easy to swap as possible. Having your old 305 heads worked a little is much cheaper than buying any new set of heads. Once you get the new heads, some will require modification or expensive intake bases to even bolt up. So YES 305 heads will work on a 350!!! They may not work as well (without porting) as L98 heads, but performance is all relative. Go to a junkyard and grab any truck 350(low compression), bolt on the 305 heads and put a small cam in it. The result is something that performs like a much more expensive engine. period.

peace

 

Oh no,, a 1996 magazine article ran an SS (that they say is stock),, it went 15.08,, now all stock SS should run low 15’s. Truly the wisdom of an engineer making 95K. I don’t have the time you apparently have,, but I’ll make it. You like magazine articles,, as an original owner of a 85SS I bought about every magazine article I could find with the SS’s in them. While I’d rather talk about actual tuning, testing, and modifying experiences, I’ll play on your level. Here’s a few magazines that tested SS Monte Carlos.

June 85 - Car Craft – 15.90 @ 87
July 85 - Car&Driver – 15.90 @ 86
Summer of 85 - Muscle Car – 16.02 @ 85.8 (best) – 16.49 worst
March 86 – Super Chevy – 15.39 – 15.57 @ 88 –89 (Vericom times)
August 86 – Car&Driver – AeroCoupe 16.8 @ 82
March 87 – Muscle Car – AeroCoupe 17.35 @ 80.4
May 87 – Hot Rod – 15.87 @ 87 (Vericom times)
June 88 – Muscle Car Review – 16.44 @ 87

Car Craft did a Mission Impossible article – 15.90 @ 87 base line - chassis dynoed peak 141 HP @ 5000, 122 @ 5500. Added 1.94 valves to heads, cam, intake, exhaust up grades – chassis dynoed at 170HP @ 5500 – first pass it ran 15.50 @ 90. They finally tweaked it enough to get it to run 14.80.

With the exception of the March 86 Super Chevy (15.39 – which I’m not sure how accurate their Vericom was) and the March 87 Muscle car (17.35),, all these cars ran right there with the 10+ SS Monte Carlos I tested and tuned on back when they were new,,, and truly stock. My SS was used as R&D for Hypertech chips,, and the 5 tested before mine,, the fastest being 16.01,, the slowest 16.7 (all coupes) also indicate these cars were a high 15 second,, low 16 second car stock. The Aeros are HEAVIER than the coupes and were not as fast, theoretical “same car” more weight,, slower. I don’t doubt Chevy High Performance published 15.08 as a time for a stock Monte Carlo. The guy doing the story could be ignorant enough to believe the thing was stock or was lying about it,, I don’t know and neither do you. If you or anyone else wants to believe that magazine car was that fast stock and can run that fast with those bolt ons,, go right ahead and duplicate it. You know,, this 15.0 “stock” SS, 14.30 with cam,,, also appears to be Ed Maher’s “buddy’s” car,, cough,, cough. I’ll ask you the same question I asked him,, do you actually believe that an automatic car weighing between 3550 – 3600 (w/driver) with an engine rated at 180HP (190HP in the Z) could get remotely close to a 15.00? I know it can’t,, I’ve seen and worked on too many of them.

I do have another question for you. On October 28,, you stated your car ran high 12s,, the same day you were asking about swapping metering rods in the stock computer controlled carb because someone said it could make you faster,, right. Did you change the metering rods between then and yesterday to slow it down to a 13.10,, or did you just not remember you said the car ran high 12s? You know,, to bad you live to far away that a buddy of mine couldn’t show you what a REAL 12.90 Monte's tail lights look like with your doors (that were blown off) following behind in it's draft.

[This message has been edited by BadSS (edited November 06, 2001).]

 

F-BIRD'88, I think we understand each other's basic points, and yes I agree that smaller port volumes (170-190cc) can create streetable HP for less $. I see the point about reusing the 305 heads if you've already got them. They will make decent streetable HP (idle to 6000RPM) for a moderate buildup of probably 300-350HP on average, and up to probably around 400HP. If you're building a 8000RPM motor, or not on a budget I do suggest aftermarket heads though. Most heads with intake port volumes of over 190cc are not practical for average street buildups, and will not respond as well without other mods. Just like 2.02 valves or single plane manifolds. There are plenty of 350 heads that do flow better with smaller port runners: 882s, L98s, etc (see previous post of runner sizes) These are the 'performance' heads I was talking about.
BadSS, as for the Aerocoupes being heavier, my SSs weigh in stock within about 200# of one another (3,473# Aerocoupe versus 3,239# Notchback). My Aerocoupe also had And the readings of ETs and MPH for different runs were not adjusted readings, the 15.08 time I referenced was. I grabbed that number from the first article I saw, and I never said ALL SSs ran that. I believe what I said was that I estimated the SSs were low 15s cars, which when the ETs and MPH are adjusted accordingly is correct. As for MY ETs, I HAVE broken 13 before, but not consistently. I average 13.10, and have ran as high as 13.6 unadjusted after my mods. http://cgi.spots.ab.ca/~monte/cgi-bi...ime_quarter_et Here are some other ETs (if the link works). My carb questions from my post on Oct. 29 were answered by several emails, and as a result my dad made alot of the changes suggested, but I haven't ran it in a quarter strip since then. I expect to break 12s consistently once it's tuned correctly. What does any of that crap have to do with 305 versus 350 heads? I don't think you've had one post about the subject matter everyone else has been discussing.

 

Jag : I think now we have come to common ground... Except those 882's. The late, light castings. They really suck. Even thou thet flow 205 out of the box, on a motor they
really miss the mark. But that's another story. Have a nice day...

 

I'm glad we finally found the common ground! The 882 flow tests from an old Chevy High Performance cylinder head special edition weren't too bad. the 151cc/76cc/1.94/1.5 heads flowed (intake, exhaust, and piped exhaust @lift"): 39, 34, and 34 @.050; 70, 58, and 59 @.100; 125, 108, and 109 @.200; 175, 135, and 136 @.300; 204, 141, and 143 @.400; 205, 142, and 144 @.500; and lastly 206, 142, and 145 @.600. The flow tests wer completely stock with no port work or polishing done to them. They stated that with 2.02 valves, the heads performed even better. They outflow the 441s and the 462s through a .400 lift in those tests, but fell flat at .500 and .600 lifts due to their smaller port volumes. They also stated that on occasions, depending on each individual casting, the 441s outflowed the 882. They flow pretty close to one another. As you can see, they aren't as bad as you'd think. If used with around a .400 lift camshaft, the crappy .500 & .600 flow limits could be bypassed with a longer duration cam and torque converter. They make alot of responsive torque, and work great for milder 300-350HP buildups. Alot of guys on montecarloss.com mill these heads down to around 60cc and put them on their L69s. They seem to work well from what they tell me. They make decent heads for a budget buildup and are in abundance.

[This message has been edited by jag (edited November 06, 2001).]

 

Jag,,, it's not that I disagree with everything you've said. However,, there are guys coming here for answers and I have a problem when guys say stuff like – “I was running 14.80’s (giving you that’s what your Aero ran) and I just bolted on a set of L98 self ported heads, intake, I took off my true dual exhaust and put on a catalytic converter and the stock cat back with the fake duals,,, dropped 200 lbs off the car (to equal the weight of the coupe),, and now I’m running 13.10 (a 1.7 second drop) with the stock unadjusted computer carb”. What a load of crap. That is what you’re saying whether you realize it or not. You ask what my post has to do with anything,,, I’m just trying to make sure some kid with a 305 doesn’t waste all the money he makes part time at the local McDonalds on a set of L98 Vette heads,,, thinking he’s going to run low 13’s with the combination you described. You’re the one that brought it up anyway,, and just what did that link show? I saw a stock SS running 15.80s, an SS with cam and ported heads running 14.60’s,, an SS with 355 and Vortec heads running 13.50’s,, and an SS with a 408 running 12.80’s,, all these seem perfectly reasonable to me.

About all I could add to F-88’s coverage of the subject applies to circle track guys using the 305 heads. The vast majority of the circle track guys are about the cheapest tight wad mothers around (no offense meant),,, and they won’t deny that. 305 heads are cheap. There are some claimer classes depending on what place you end the race in,, you can “claim” the winner’s engine for $500. Most are not going to spend a lot of money on hard to find head castings,, since they’re going to port what ever head they run. Really,,,,, the only guys that win on a regular basis (around here anyway) are the guys that have a machine shop,, the guys being sponsored by a machine shop,, or the ones that at least know how to port heads,, and /or are willing to take a chance and sink a lot of money in a engine that they could loose for $500. Some machine shop guys will take the 305 heads (cheap and plentiful) and use 1.99 / 1.57 Oldsmobile valves,, using the stock hardened seat in the 305 heads. The Olds valves are shorter,, so they don’t have to buy longer push rods to run with the mechanical cams,, but you do have to machine the rocker pads. You can also shape the 58cc chamber into a nice chamber design,, and stay around 62cc. Heavily porting the pocket area and blending that into the runners,, along with the “high dollar” looking and functional 62cc chamber design,,, you now have a head that will hang right there with a similarly ported 2.02/1.60 (with 68cc chambers),, and all they have in the heads is their time and a set of valves and they don’t have to buy longer push rods. I’ve seen 406 engines with these heads (done right) making best guess 425 horse range,, and would estimate flow in the neighborhood of 235 cfm around .550 lift (which is close to F-88’s numbers). However,, these sure wouldn’t be very cost effective if you had to pay someone to do all the work. Although,, a lot of machine shops when faced with idle time,, they’ll “work” a set of the no sale 305 heads,, do these tricks, and sometimes you can pick up a set semi-reasonable. The only problem with that is if you don’t know what to look for,,, you would really have no idea the amount of time spent on heads,, or what to expect from them. At least with a cost efficient box stock head like the Vortecs you pretty much know what to expect once you bolt them on.

[This message has been edited by BadSS (edited November 07, 2001).]

[This message has been edited by BadSS (edited November 08, 2001).]

 

BadSS: Thats where my 305 heads ended up.
On some guys 406 55 chevy. I gave him a full money back guarantee, they would perform as stated. Never heard from him again so I assume he was happy. Am working on two other sets now in my spare time. Going to try David Vizard's 30Deg valve seat angle trick for grins. I pick 'em up for $20 a set. The first set I pulled out of the garbage (broken guide boss).

[This message has been edited by F-BIRD'88 (edited November 06, 2001).]

[This message has been edited by F-BIRD'88 (edited November 06, 2001).]

 

Very intresting thread so far. I had a set of worked 305 heads on my 355 in my old 85 Z28. It had the standard bolt ons (headers, exhaust, performer intake, 600cfm carb, etc) cam was a 222@050" .467" list with a 110LSA. The car had 4.10 gears, 700R4, and a stock suspension.It ran quite nice, excellent throttle response and excellent gas milage. I'd get 400-450 kilometers on a tank of gas, with the 4.10s. Best run was a 13.7@101mph.

I've got several sets of 305 heads at home in the basement waiting for some port work. I've got a set of my 350 in my TA, but they are comming off for some port work as they are stock now. You can generally get them for nothing, and if you do your own port work, the are an excellent low buck alternative.

------------------
Current
86 TA 350 TH350, hardtop
99 Ducati 750 Super Sport
76 Yamaha RD400 track bike

Former
85 Z28
94 TA

 

That's the "sleeper factor" I was talking about....

 

jag,

I was just wondering if you would have a quick second to answer a question for me.

Does the "Tornado" flow duew-hicky thing work? I figure since you have a degree in air flow stuff, then you would at least be able to understand the principle behind this thing. I can't.

Also, does the "Turbulator" exhaust tip work. It claims to increase backpressure at low RPM, and therefore increase low RPM torque and MPG. Would this thing work? It's a nice thought. Maybe it does work.

Thanks,
AJ

 

"However, these sure wouldn’t be very cost effective if you had to pay someone to do all the work." That's what I've been saying. Some people can do their own work while others can't. It is important to note that mild porting & polishing is not hard for anyone to do http://www.sa-motorsports.com/diyport.htm , but major porting and polish should be left to professionals, it's easy to screw up a head. Anyway, anyone reading this and wanting to build a performance engine (any size or type/stock or modified) should stick to the performance basics with their money before looking for new heads. Good areas to spend money effectively are 1. Suspension & braking (Most people use older cars with alot of HP loss into the body's worn suspension, and you have to be able to stop so check the brakes out, 2.Exhaust (less restrictive mufflers, high flow or no cat, headers, 2.5" pipes lead to the best HP gains for the $), 3. Intake (cam & lifters (something 200-220 degree intake duration and around a .450 lift for example), intake manifold (usually dual plane for street driveability), heads (as you can read from the other previous posts, for lower HP (less than say 350-400) more driveable street engines 170-190cc intake port runners with smaller 1.84/1.94 intake valves, and for higher HP (more than 350-400HP) use GM performance heads such as Vortecs, LT1s, LT4s, L98s or aftermarkets such as Trick Flows or Airflow Research. Cylinder heads are the best investment for your engine after exhaust and intake criteria previously listed, and are the #1 limiting factor of HP in most engines. 4. Other areas to spend money effectively, depending on the individual application usually include ignition, clutch/stall, and weight loss). The "Turbulator" exhaust tips I have never used, but I wouldn't expect to gain much, if any, HP from changing an exhaust tip. It might change the sound of your exhaust, but don't expect more than that. What "tornado" thing are you talking about? Swirl ground valves create kind of a tornado effect on airflow in the heads, and this does result in better airflow (and fuel mixture). If you want to increase MPG, HP, and response, exhaust is where to start. Replace the mufflers with higher flowing ones first and 2.5" pipes make a good investment also, next either gut the converter or replace it with a Catco or PFP high flow version (gutting it depends on whether or not you have to pass emissions where you live), then add headers. Don't worry about the heads until your exhaust and intake work is done. They are more restrictive than the heads most of the time. Do what your budget allows, and make every dollar count for HP.

 

What are swirlflow valves ??
nobody I talk to ever heard of them. I've heard of swirlpolished, and they say they don't cake up with carbon so much.
I'm confused, are you saying that air spinning around in a circle flows into the chamber better? this will make more power right?

 

Swirl valves are what I call valves that have been swirl polished. They promote better airflow for little more money than stock valves. The carbon thing may be true, but the swirl polishing gives the airflow more of a twisting or tornado styled airflow into the combustion chamber giving faster airflow compared to non-swirl valves. Faster airflow gives more HP, but about the same torque. Larger valves give more torque. I think they run around $10-15 higher per set of 8, but are well worth it for any application. There are also different degrees of cutdowns that can be purchased where the valves are cutdown around the combustion chamber area allowing better airflow. Cutbacks have proven through bench flow testing to flow up to 35% more air, and are also lighter.

 

The "Tornado" thing is a little 'fan blade' that you put in the air passages going to the carb/TB. They don't spin like a fan blade does. It's a fixed unit. You can either put them into the duct going to the intake system, or for people like me that have a TB or a carb with a 14" by 'x'" air cleaner, they make an insert that promotes swirl before the air even goes into the TB.

They claim better HP, MPG, and smoother acceleration. Everyone on here seems to think that it's a load of crap. Although I've read a CHP article that they put one in a S-10 with a CPI Vortec 4.3L V6 and they picked up 8 RW-HP. They also stated that they've added one to a LT1 and had no improvement at all.

It's not that I want to buy one, or the "Turbulator" for that matter. It's just the claims that the manufacture of the "Tornado" makes could hold some truth. Obviously not in every engine/combo, but perhaps some.

AJ

 

so swirling air moves faster than straight air? I've never heard of that kind of engineering before.
I have seen swirl polished valves and they are smooth and do not have grooves and there's no way they could cause air to spin, so I cannot agree with you on that one.

If spinning air moves so good then why don't racecars run those tornado things? and why don't the factory make the air swirl?
just wondering maybe the obvious.
thanks


------------------
1986 Iroc 305 small block chevy getting modded now for speed

 

that tornado thing is just another make you waste your money items. hot rod tested it and it made absolutly no gain in power or gas milage.

 

The question was: will 305 heads make more power on a 350. Answer yes they will make more power on a 350 than on a 305.

 

Good Answer

 

I never said that. Did I? I just wrote what I read.

The swirling of the incoming air does increase efficiency. That is why GM used the swirl port heads for a while. If you increase efficiency then it increases the VE%, which should decrease lost power.

I can understand how it works on the valves and even in the ports, but to say that it works before the intake manifold? That's what the "Tornado" people claim.

Why it worked on the Vortec 4.3L CPI, I don't know. Maybe they also cleaned out some leaves that were stuck in the intake duct coming into the air filter? Who knows.

I was just asking jag because he has a degree in air flow. Maybe he would better understand the theory involved here. That's all.

AJ