TBIThrottle Body Injection discussion and questions. L03/CFI tech and other performance enhancements.
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I have a gut feeling that the dual pattern cams aren't "right" for swirl port heads. My reasoning is simple. All together SMC exhaust ports are crappy and the intakes are good. Then came the swirl port heads. They have the worst intake port (in my opinion). So how about using an single grind like a 210/210 and .450/.450 cam. If the car has headers it should feel really good.
The only reason I'm thinking along these lines is from the experience of others. If you look at the newest grinds for the LS1 engines you'll notice the fast guys are running with equal if not MORE duration on the intake. The reasoning has been that the exhaust ports on the LS1 flow so well that it's the intake restricting power. The swirl port TBI heads have the opposite going for them. All together the exhaust ports aren't pretty but with headers and a 3" cat-back it works well.
Does anybody run or know somebody running a single grind and have results?
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I don't know that the swirl ports are as limiting as one might think. The only reason I say this is because I’ve measured one. Even with the extra metal in the intake runner it still came out to 168cc's. That's darn close to the Vortec casting with 170 cc’s.
Granted the portion of the port that's filled with the extra metal does protrude into the port and would certainly interfere with flow, however, you can look inside the port and see that the roof on the runner is quite a bit higher than other castings. The neat thing is... guess where a lot of engine gurus (such as David Vizard) suggest that you remove metal from the intake runner? The roof.
Coincidence? Perhaps. Actually... more than likely.
I can see where you’re thinking is going with this, but keep in mind that even the BETTER (not BEST) aftermarket heads still have a exhaust-to-intake ratio difference of 80-85%. It’s not until you get up into that area that you no longer “need” a dual pattern cam. I doubt the percentage of the swirl ports (even with the “loss” of intake flow) is much over 75%.
It’d be interesting to have some of those heads flowed to see how bad they are. Although I doubt anyone would spend the $$$ to ever do it.
The set I have now are off an LO5 (#14102193) that I’m going to put in my ‘83 ½ ton pickup. I plan on yanking a TBI system off a car/truck and use it for ease of drivability, as well as MPG. If you can believe it, I’m actually pocket porting them as well. I got them off a 500 mile engine for $100. Might as well make the best of them, right? However, I’m still going to use a dual pattern cam. I’m gonna keep it low duration for more low RPM torque, so it’s hard to say if it would better or worse since the cam isn’t gonna allow “a lot” of flow anyway.
Originally posted by AJ_92RS
However, I’m still going to use a dual pattern cam. I’m gonna keep it low duration for more low RPM torque, so it’s hard to say if it would better or worse since the cam isn’t gonna allow “a lot” of flow anyway.
I had an L05 with a Ram Jet cam in it and it was a blast...I could stomp anything off the line to about 40 mph then it ran out of steam at the top end
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well if the lo3 heads are so bad why does everyone say they flow very well??? i don't understand and i have searched this b4. and i still don't get it. you say they flow 168cc and they are almost as good as the vortecs. then why would you get rid of them if they flow good.. also what can be done to improve them. like you were saying to raise the roof on them. is that all you can do?.
i looked into buying tpi heads and also vortecs. but if they weren't an option what could i do to these heads to make them better... thanks for any info you can provide!!!!
The 168cc he mentioned isn't the flow of the heads. It's the size of the runners. From what I've read the swirl port design is used to make low end torque. That disturbance is great for getting you off the line, but for high rpm power the swirl port turns into a wall of blocking flow. That's part of the reason why tbi's can get out of the hole descent but can't breath above 4500 rpm's.
When I put on my Vortec's along with the cam and intake I lost most of my low end, partly because of the cam but I think the different head design changes the powerband as well.
Originally posted by 92rsv8 well if the lo3 heads are so bad why does everyone say they flow very well??? i don't understand and i have searched this b4. and i still don't get it. you say they flow 168cc and they are almost as good as the vortecs. then why would you get rid of them if they flow good.. also what can be done to improve them. like you were saying to raise the roof on them. is that all you can do?.
i looked into buying tpi heads and also vortecs. but if they weren't an option what could i do to these heads to make them better... thanks for any info you can provide!!!!
i dont think anybody suggests keeping the swirl port heads that came with LO3s for a performance application
Originally posted by V8Astro Captain I had an L05 with a Ram Jet cam in it and it was a blast...I could stomp anything off the line to about 40 mph then it ran out of steam at the top end
What rpm did the cam fall off at? I was thinking of using that cam in a tow vehicle (chevy Tahoe) in the future. Do you think that would be a decent cam to go with?
Have you ever looked at the specs on the ram jet cam. I think is something like 196int 206exh and .450lft. It's not much differant than a stock vortec cam.
The reason you seem to see so many dual pattern cams is because thats what the aftermarket is catering to. With the swirl port heads, the intake runner volume is quite high to compensate the loss of final velocity of the incoming air/fuel. Remember it's not volume but velocity that makes the power. I think this single pattern camshaft theory is a good one; it will compensate the loss of velocity on the intake side but generating more valve duration for the 'slow' incoming air/fuel. We just need a guinea pig now
Originally posted by steve8586iroc Have you ever looked at the specs on the ram jet cam. I think is something like 196int 206exh and .450lft. It's not much differant than a stock vortec cam.
Steve
A stock Vortec cam is 202/207 .410/.424 lift 115° LSA.
The Ram Jet cam is 196/206 .431/.451 109° LSA. IMO the Vortec cam has too much LSA and not enuf duration. I would say that the LSA is what saves the Ram Jet cam. I can't really comment on the Vortec cam as far as performance, but I can on the Ram Jet because I had one for close to a year. In fact, I bought another one to put in the 310 I'm having built...yes I liked it that much.
JokerRS, to answer your question...with the stock L05, Ram Jet cam, Holley Pro-Jection intake and headers it was done pulling around 4800 rpm. The low-end was awesome...I miss it...
BTW, I thought I'd include a couple of pics of the heads I'm toying with just so those who aren't familiar with a "swirl port" will know what it is.
In this pic I circled the casting number in orange. I also drew a couple of red arrows in the intake ports so you can see the direction of airflow, as well as how much that “ramp” (for lack of a better word) protrudes into the intake port.
yes and no, it did what they wanted it to do, TBI cars with swirlports make great torque (i have the dyno sheets to prove it, then putter out just enough for an overweight TPI car to beat them, but they gave the TBI enough grunt to make it feel fast.
Originally posted by Dewey316 yes and no, it did what they wanted it to do, TBI cars with swirlports make great torque (i have the dyno sheets to prove it, then putter out just enough for an overweight TPI car to beat them, but they gave the TBI enough grunt to make it feel fast.
Could you prove it for us.
Kevin's dad slapped on a TPI onto the L03 longblock and got lots of low end grunt, more so than TBI. Personally I'd rather see results from either a comparative dyno session or track times.
You can tell me the heads aren't all that bad but I can tell you they are! You talk about port shape and what not but the most critical area's of the port are closest to the valve seat!!! You also can't say that because the volumes are similar that they are just as good. Look at a set of vortec heads and you think swirl ports will flow comparitively, .
Those heads don't produce "low end" unless you are measuring torque from 500rpm to 1000rpm because everywhere else a good set of heads will make more torque.
I think what's happening is that the big picture isn't being taken into account. Those heads are a performance bottle neck in OEM form. NJSpeeder swapped heads and was running 14.2's with exhaust and a performer intake. You can't tell me swirl port heads with headers and a intake will get you running 14.2's let alone mid 14's. He had also lost compression and running aluminum heads is another draw back.
I'm not saying the heads should be the first thing to be replaced on a stock RS camaro but I am saying they suck. Porting can help but it isn't worth the price in gaskets to rebuild em. It's like a 305 that needs a new rotating assembly.
I still think a single pattern cam is worth a try. You'll loose some resonance tuning with the extra intake duration and mild intake manifold but the extra open time should let the motor pump more air/fuel.
i am not arguing that the swirl ports suck, i know they do, we all know they do, and your right, it may not be the head design that gives it the torque, but my local car clubs dyno day, my lo3 put down as much or more torque below 3k than all but 1 of the 305s that dynoed, the combos ranged from stock TPI to carbed. it also had more than a couple of the 350s. but we could see about 3k the l03 had nothing. now why it did this i don't know, i haven't taken the time or effort to swap on a pair of stock TPI heads, with everything else untouched to see the diffrence.
Originally posted by AJ_92RS Actually there are two "Vortec" cams I've seen.
I see...
That second spec you posted is almost the same as the Ram Jet cam. I see where yer comin from.
Also, thanks for the pics
JPrevost...I found some specs on a stock cam for the '95 302 Mustangs. They run more duration on the intake side. I found alot of r!cer cams in my Comp Cams catalog that have more intake duration than exhaust. This is just a guess, but I don't think the intake side benefits as much from scavenging as the exhaust does.
Mustangs and imports don't suffer from the exhaust problems that SBC's do because of the cylinder head design. Plus due to the fact that they have a higher RPM range (Mustangs due to the short stroke and imports because of small engines) their goal is to allow the engine to pull in air/fuel easier at higher RPMs.
As you well know, the pistons push exhaust out. That's why exhaust valves don't have to be as large. This happens at any RPM. (Granted there are pumping losses involved, but that's another subject.)
At higher RPMs there's less time for the air/fuel to be drawn into the cylinders. Air only moves so fast, so the engine needs help in order to pull in as much air as possible with less time. SBC's have always been known to do this by increasing overlap in hopes that the exhaust scavenging will further increase pressure drop in the cylinder.
Since overlap makes a car less "streetable" due to lack of vacuum at idle, they (Mustangs and imports) increase the amount of time the valve is open (as well as how much it's opened) so it's easier for the piston to draw in air/fuel even with less time at higher RPMs.
This is basically just my theory. Mustangs have always come with either a dual exhaust system, or the car makes it very easy to run an aftermarket dual exhaust. That takes care of the exhaust flow. Since that's taken care of rather easily, the only other objective is intake.
Of course imports don't have a problem with exhaust since a pea shooter is large enough for 2 liters or less.
Hey guys, I am a novis by all meaning of the word so if i sound stupid bear with me because I am at this point. However I do have the interest in learning so please be patient. My only thought on the subject is this, one person stated that the intake runner is about 168cc and just from reading jegs and summit looking at aftermarket heads I know that number is respectable, maybe not "good" but respectable, but I also saw the pictures that were posted of the heads and what makes them "swirl".. so hypothetically I would be inclinded to think if you simply had them machined and gound off that ridge they wouldnt "swirl" anymore. I dont know if I am on the right track or not but im trying. My thought was if you have the intake runner size at 168cc and get rid of the swirling motion that is preventing the car from breathing up top you would have a good head. I dont know what other obstocales the head has but those were the two i picked up on .. good intake runner size but bad flow characterisitics due to the "swirling" motion created. And JVprevost (sorry if i spelled wrong) I would be a prime canidate for you cam experiment. I have stock TB, intake, heads,cam, block.. I would be happy to install a cam that would give you an idea of your theory.. i have time slips of what my car currently runs and the ability to run it directly after the swap also.. just an idea and just my opinion guys, now pick it apart and let me know how im wrong I have alot to learn so keep up the technical conversations because you dont realize how much education you give from them.
Scott Rooper
Originally posted by JPrevost Could you prove it for us.
Kevin's dad slapped on a TPI onto the L03 longblock and got lots of low end grunt, more so than TBI. Personally I'd rather see results from either a comparative dyno session or track times.
After doing the L03 thing I put a pair of those heads (193's) on a '96 Vortec 350 short block. It made 210hp & 330tq. to the rwhls. I then did some porting experimenting on them. You're right on the 168 cc's I had them flowed beforehand and was shocked at the results....178 intake 146 exhaust ( on a standard Super Flow) I was able to increase the cc's to 175 and the flow to 196 intake and 183 exhaust (didn't measure ex. cc's). I put them back on and went back to the dyno....250hp & 335tq The car ran 14.07 previously and 13.70 after, this was using an LT1 cam and 1.6 rockers on the intake. I know it had more in it but I didn't spend anymore time on the project. So in conclusion they may not be real good heads but they do perform with a little work ( I didn't spend alot of time on the porting, just roughed them out but polished the ex.).
Don>>>
Originally posted by Duke They must have been smoking crack when they came up with that head design. Swirl port, lol.
Read either of the books by J.B. Heywood or R. Stone and you'll understand why they did what they did. There are very good reasons for it. 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).
Originally posted by Dyno Don 178 intake 146 exhaust ( on a standard Super Flow) I was able to increase the cc's to 175 and the flow to 196 intake and 187 exhaust (didn't measure ex. cc's).
Don,
Just curious... what lift was that? The .450" lift since that's about there the LT1 cams lift, or was it at .500" lift?
BTW, good numbers with that car. You obviously have/had other things done to the car also.
178 intake,145 exhaust. that's pretty respectable for a crappy swirl port head. not too mention a 305 head. stock 882 76cc 350 heads can't even do that with port and polish on both sides.
Originally posted by jasonbennett 178 intake,145 exhaust. that's pretty respectable for a crappy swirl port head. not too mention a 305 head. stock 882 76cc 350 heads can't even do that with port and polish on both sides.
193's are not "305" and 882's are alot better than that. They came on 'vettes and are listed as one of the better heads to modify (except for the large chambers).
882' and 624's suck htey can be made to run good if you know where to port and polish them. the mirror polish really hurts the flow on the exhaust side of the head. these haeds are very prone to cracks. they are the first of the lightweight castings.
Originally posted by jasonbennett 882' and 624's suck htey can be made to run good if you know where to port and polish them. the mirror polish really hurts the flow on the exhaust side of the head. these haeds are very prone to cracks. they are the first of the lightweight castings.
Care to explain how polishing the walls in the exhaust port "hurts the flow"? That's a new one on me.
I suppose I should stop washing my car. The clean finish hurts it's aerodynamics, right?
if you would have read the whole sentence, i said "mirror" like finish. it doesn't provide enough trubulance to get ultimate flow from the port. you don't want to mirror polish them you want the marks left over from the polish with a carbide tip.
on the intake side you want it slightly ruff. i am porting/polishing a set of heads right now, i have the full SA kit, i know for a fact that in the kit they give you everything to do a MIRROR finish on the exaust, but on the intake the highest you go is a 400 grit cartridge roll, that gives it enough textures so that the fuel will stay atomized, and not create droplets on the walls of the intake ports. you also want to polish the combustion chamber. the idea behind polishing them is 2 fold, 1) flow, 2) it helps to keep carbon build-up down, but i hear on a street car it doens't take long at all for it to build up , even with a great finish.
I have a gut feeling that the dual pattern cams aren't "right" for swirl port heads. My reasoning is simple. All together SMC exhaust ports are crappy and the intakes are good. Then came the swirl port heads. They have the worst intake port (in my opinion). So how about using an single grind like a 210/210 and .450/.450 cam. If the car has headers it should feel really good.
The only reason I'm thinking along these lines is from the experience of others. If you look at the newest grinds for the LS1 engines you'll notice the fast guys are running with equal if not MORE duration on the intake. The reasoning has been that the exhaust ports on the LS1 flow so well that it's the intake restricting power. The swirl port TBI heads have the opposite going for them. All together the exhaust ports aren't pretty but with headers and a 3" cat-back it works well.
Does anybody run or know somebody running a single grind and have results?
i run 480/480 cam in my race car with 193 heads 1.94/1.50 valves.good bottom end . top end is lacking. going to try 2.02/1.60 valves 507/507 lift 247/247dur. machinest open the intake port up from the seat all the way down to the end off the ramp. did not touch the ramp. looks like the fuel will come off the ramp and go around the valve and out better. rules will not let me port or polish.
ok guys, i've got a real dilemma on my hands now....
I'm in the middle of building a TBI 350 for my 'bird. I'm at the point where I need to find some heads and intake options here. I want to go vortec heads, and the $400 intake was holding me back from it. Now I found one locally for $130 and am doing some more research, and I find this thread.
My 350 has the 193's on it right now. It crossed my mind to open them up a bit and use 'em with an edelbrock intake, but all i heard was how crappy they were, only low end, etc.
My question for you guys is this: Should I sell the intake for a profit, port the heads, buy the tbi performer intake and take the gamble that it'll make power through a decent portion of the rpm range? I'm not too deep to go back, but the stock heads are for sale locally, and I can't afford to take a huge stupid risk like lose my deal of the century with that GMPP vortec/tbi intake.
ok guys, i've got a real dilemma on my hands now....
I'm in the middle of building a TBI 350 for my 'bird. I'm at the point where I need to find some heads and intake options here. I want to go vortec heads, and the $400 intake was holding me back from it. Now I found one locally for $130 and am doing some more research, and I find this thread.
My 350 has the 193's on it right now. It crossed my mind to open them up a bit and use 'em with an edelbrock intake, but all i heard was how crappy they were, only low end, etc.
My question for you guys is this: Should I sell the intake for a profit, port the heads, buy the tbi performer intake and take the gamble that it'll make power through a decent portion of the rpm range? I'm not too deep to go back, but the stock heads are for sale locally, and I can't afford to take a huge stupid risk like lose my deal of the century with that GMPP vortec/tbi intake.
What do you think?
Go Vortec, there the best GM production heads for small blocks. Unless youre really tight on money or something.
And wow, i just realized this thread was raised from the dead.
Although I doubt anyone would spend the $$$ to ever do it. 
They both could be, albeit different years, OR one's for a 350 and the other is for a Vortec 305. 
.
