Fat Kid

Now, this is for my truck, but if it makes you feel better the TPI intake was from my 87 GTA. Now, my T/A had a tpi 350 in it. long story short, crashed the car, parted it out, now i have a 91 GMC with tbi (speed density) and a tpi intake and computer (mass air) from a trans am. both motors were 350's.

what i need to know, is what do i all need to do? i think i am going to use the truck's computer and wiring and the t/a chip (modified for no vats and no mass air). I'm not sure, but i think it might work better if i put the fuel and air settings on to the tbi chip. is this possible?
as for wiring, the injection systems are pretty much the same. the various connectors/plugs are very similar if not the same. as for wiring the injectors, i figured i could put the leads to one tbi injector to one bank of tPi injectors, and the same on the other side. i am certain this would work.
my main concern is with the computer programming, and other things my feeble mind doesnt know are different between the two. I would just like some difinitive answers that i havent been able to find on other corners of the web (even here!).

thanks in advance!
-Max

thirdgen88

You can't use the TBI computer for a port-injected application... The thing to do is to repin your harness for a TPI computer (Speed Density TPI would be the easiest, 1227730 ecm)..

Go here for details:
https://www.thirdgen.org/techbb2/sho...+harness+repin

They have a procedure for going from the '747 ECM (what is probably in your truck) to the '730..

kevinc

It doesn't.

dimented24x7

iTrader: (2)

The defintive answer is your going to need the entire setup off of your GTA or some other car that had tpi. You only have a few little bits and not the whole thing at the moment. No part of the tbi system will work with the tpi system and vice-versa. The computer issue will probably be the least of your worries as it only plugs into the harness. You need a wire harness, injectors, lots of misc. fuel system parts, new fuel pump, ecm, gaskets, etc... Youll be nickle and dimed to death if you try to peice it together. It might be possible to reuse some of the wireharness, but getting one meant for tpi or an aftermarket would be easier.

A 7730 SD setup would work provided your using a mostly stock L98. Once you put it on a modded motor, using a stock ecm with a stock cal. becomes a real hit or miss situation. Youd need to tune it to get the engine to run right.

If your just looking for an extra 20-30 HP, then working with the tbi will be easier and cheaper. Once youve done all the typical stuff, theres alot of stuff in the stock calibration that can be changed that will radically alter how the motor runs. FYI, even with just bolt ons, an L03 can drop from high 15's to mid 14's. That should tell you how restrictive the stock intake/exhaust/gearing is.

Fat Kid

i dont know why you have to be a ***** about it....i mean, i had a trans am (how i found out about this board). i dont understand why people have to be so closed minded...

anyways, i have the stock computer from my car...stock L98 tpi (MAF). in my truck is the tbi setup (speed density).

the one thing i'm wondering is, since almost all the sensors/whatnot are the same (minus knock sensor), can't i just wire up one bank of injectors to the wires to one tbi injector and the opposite for the other side? then, hook up my map sensor and all the others? i mean, woulnt i just have to tell the tbi computer that it is getting more air/fuel? i dont understand how that wouln't work???

dimented24x7

iTrader: (2)

You could just wire one and one or both banks up to one of the drivers in the tbi ecm and cross your fingers that it works well when you start it, but the overwhelming odds are that it wont even come close. There are many fundamental differences in how a dryflow behaves vs. how a wetflow system does, and thats reflected in the algorithms that run in the ecm. Could it work, sure. With lots of tuning you could probably get it to work alright. The easiest solution, though, is to just pay a little extra and do it right by getting all the tpi related parts for your tpi conversion.

thirdgen88

Did you even try to read the link that was posted to help you?? That procedure is the most direct way to achieve what you are trying to do.. And again, you CAN'T use a TBI computer in a port-injected application.. I'd recommend against doing that procedure (or messing with your truck at all) anyway, because unless you learn a lot more about the way things work, you won't have very much success..

You say that you don't understand how that wouldn't work.. This implies that you do understand how it would work.. Explain how you would accomplish it if you understand how it works...

If you're unwilling to do any of the research to learn the things you need to know, there's no point in continuing this conversation further...

kevinc

Because the more 'open minded' boards that let anyone post anything are complete trash. Jammed up with posts about trucks, mom's station wagon, SUVs, etc.

The name here is thirdgen.org not thirdgen_and_anything_else_resembling_them.org

But since you're here, let's try to help.

I say you can use your TBI computer, the other guys are trying to throw you off. Just wire up the sensors, change the cylinder volume constant to 350ci, and away you go.

thirdgen88

dimented24x7

iTrader: (2)

I would assume he's joking but at best youd just be throwing fuel and spark at the motor with the tbi ecm. The tune would be off as the tpi intake will change the ve, spark requirements, etc. of the motor. It can be made to work, but the easiest and best solution is again, to get the right parts for the job.

Fat Kid

yes, i did read the entire thread top to bottom. i was just wondering if what i thought had been considered yet. thanks for the serious answers tho.

as for kevin, i brought up the subject of a tbi to tpi conversion....it just happened to be in my truck instead of a thirdgen. i mean, i got the stuff from a thirdgen that I had...so i dont see what the problem is...at least everybody here doesnt share the same views as you.........

thanks guys!

kevinc

What you typed:

What I saw:

You're welcome!

five7kid

iTrader: (14)

Well, Kev doesn't make the rules. Neither do I, I just enforce them.

We're allowed to make allowances if it can be called "3rd gen related". Having a 3rd gen base or computer isn't adequate.

Since there are those who go out and get a TBI 350 from a truck and may have similar questions, I decided to let this one live. If it continues to be a flamefest instead of a techfest, then you can be sure the will soon follow.

ShiftyCapone

iTrader: (7)

I would stick with the TBI and mod that. Swapping to TPi won;t gain you anything really. I would use the L98 heads and cam on your current 350 TBI if you still have access to them. TPI makes for a good truck motor but so does TBI. Dyno charts show minimal gains going from TBI tp TPI. The real problems are with the stock heads cam and intake. You can make more power with less than money than with the stock GM TPI.

CLiff notes: Stick with TBI or convert to another form of multi port that won't choke your motor.

kdrolt

Dyno Don did a test where he tested a 305 TBI engine in a 3rdgen Fcar and dyno tested it; some months later he emoved the TBI assembly and replaced it with a TPI intake, throttle body, and appropriate ECM. He left everything else the same (block, cam, heads, exhaust).

The engine with TPI installed made 70 more ftlbs and 18 more hp on a chassis dyno than it had when it had TBI. IIRC the TPI test was done in colder month than the TBI test, and I think the difference in hp would have been around 5 hp. In other words the TBI might have made 161 fwhp instead of 156. I think two different dynos were used as well, but I'm going to ignore that because there's nothing that can be done about it. The test, however flawed by resources and time, was the best comparison test ever made by any TGO member especially since it tread on the tricky TPI-TBI issue.

In any event and IMO the test proved two things which I summarize as:

1. the TPI intake manifold + filter, in stock form, has less air breathing friction than the stock TBI intake intake + filter, because the TPI engine made more power. TBI uses the same intake manifold on a 350 as on a 305, and the TPI intake/runners are the same on a 305 as on a 350 --- so they are both more air challenged on the 350 than on a 305. So you should get the same type of result if you did a 350 TBI-TPI test.

GM actually did that test: the police 9C1 LO5 engine (1992-1993) used the L98 cam and made 205 fwhp and 300 fw ftlbs. The L98 engine (more correctly called the B2L), as used in the Fcars, was rated at 220 fwhp and 320 fw ftlbs during it's first issue. Yes I know the heads were different, but the L98 iron heads don't flow that much better than the iron 193 swirl port heads on the LO5. The point is that the TPI intake, viewed as an air mover, has less loss than the TBI intake manifold.

Back to Dyno Don's test: For the TBI: 156 fwhp corrected to 161; 174 fwhp TPI; so it's a +13 fwhp difference in favor of the TPI. It would be interesting to flowbench test a stock TBI intake manifold to see if it flowed 7% less than the TPI, which would confirm the dyno measurements. TPI intake/runners has been previously flow tested by a car magazine (Car Craft?) and the data appears on TGO if you search for it. The +13 hp gain for the TPI also compares well to the LO5-9C1 vs L98/B2L (205 fwhp vs 220 fwhp, a difference of 15).

2. The TPI intake manifold makes a lot more mid range torque in stock vs stock form (70 fw ftlbs raw data; but more like 55 ftlbs after temperature correction). The single-plane 48mm dia bore TPI uses equal-length runners and only two tight turns (plenum-to-runner, valve throat) so it gets a big acoustic boost in cylinder-filling near 3000 rpm and not much friction. The dual-plane TBI with a 43mm diam bore uses unequal length runners so there is no single rpm for boosted cylinder filling, and there are at least 3 tight turns (under the TBI, from the mini plenum to the runner, valve throat) so there are more flow losses on TBI than on TPI. Again it looks like, after temperature correction, the TPI is 7% better in torque based on Dyno Don's data and the GM data looks more like a 10% gain for TPI vs TBI. 7% is close enough to 10% to confirm the results. In the L98/B2L vs LO5/9C1 comparison, it's 320 fwftlbs vs 300. The difference is only 20 ftlbs (vs 55 in Dyno Don's test), so I'll guess that some of that is made up for by the better combustion of the 193 head.

So in stock form, TPI does outperform the TBI even when the rest of the engine is identical. Period. Kevin91Z posted most of the results done by his dad (Dyno Don), per these two main threads on the subject:

https://www.thirdgen.org/techbb2/sho...threadid=22270
https://www.thirdgen.org/techbb2/sho...threadid=40212

Both can be modified to improve power, but there is a long list of issues + costs for both designs, because both TPI and TBI have their own warts. And though the swap from one to the other isn't that hard, it can be for the inexperienced. So sometimes keeping things simple is better, so long as you can live with the results. FWIW, HTH.

Fat Kid

if that's true, then ban that idiot kevin... i didnt make this a flame-fest, he did. i could have lied and said this was for a thirdgen and nobody would have known the difference....at least there are some people willing to help.

kdrolt, thanks for the advice and the serious answer!!

dimented24x7

iTrader: (2)

With all due respect, that conveniently skips past that whole problem of what happens when your out of the rpm band that those intake runners resonate at. Namely the lack of low end torque and plummeting power above 4000 rpms. Aftermarket intakes will cure this and turn the crusty tpi into a solid high performance induction system, but then we're talking $$$. Another option is to put together a DIY-mpfi system. Both good solutions.

Just my opinion, but comparing stock tpi to a stock tbi is like comparing two piles of dog poop. One might not smell as bad as teh other, but theyre both still piles of crap.

Back to the topic of doing the conversion. The closest thing your going to come to a bolt-on stock system is the MAF tpi. It has shortcomings of its own but itll be more forgiving of being bolted onto a completly different motor then it was origionally on. The L98 is a 300 HP longblock with decent heads and a better stock cam. The L05, well, to put it bluntly, the L05 is one of the worst 350's ever made. Has lousy flowing heads and a teeny-tiny cam. The 7730 will work well and is one of the best ecms available, but its SD and it must be tuned in order to realize the full power potential (fancy way of saying you need to mess with the computer). There have been people who've swapped over to SD tpi from tbi and found that the car was just as slow because like the tbi, the tune was way off.

At any rate, make sure you research what you need to do before diving in. No part of your present induction system will be compatible with tpi. You need a complete setup in order to get it to work.

SSC

Ebay or sell the TPI and harness to some local street rodder that thinks it looks cool. Get a Holley TBI to MPFI conversion kit made to work correctly with no hassle, fairly inexpensive as go fast parts go. This way you make more power and have less down time.

kdrolt

The TPI still made more power than the TBI did even after the rpm band you describe --- so that also means the TPI made more torque (via torque = hp*5252/rpm). Said differently, the entire torque curve on the TPI would be above the same curve of the TBI.



Two statements, and with all due respect - both wrong.

A) The 9C1-version of the LO5 used the L98 cam. 773 (suffix) part number, IIRC, it's listed in the GM P & I books for the Bcar, and it was confirmed by removal from a 93 Caprice 9C1 (LO5 engine) and followed by micrometer measurements on the cam lobes. If you call it tiny -- fine, but it's the same cam used in the L98.

B) Read this thread for TGO-sourced data on the LO5 (193 casting) vs L98 (083 casting) head flow; or condensed here for the 350 heads:

---
Stock (unported) peak cfm's summarized L to R by: casting number suffix (last 3 digits), material, RPO code, cfm peaks for intake & exhaust and the (owner). The owners (or thread poster of the info) ME Leigh, smithtc, rhuarc30 and Dyno Don are all from TGO threads:

350 heads, stock
083 iron L98 head: 185 intake; 106 exh (smithtc)
083 iron L98 head: 194 intake; 118 exh (rhuarc30)
083 iron L98 head: 202 intake; 141 exh (F-BIRD88)
113 alum L98 head: 199 intake; 159 exh (Chevy High Performance)
113 alum L98 head: 182 intake; 145 exh (Vizard book, p124,127)
193 iron LO5 head: 178 intake; 146 exh (Dyno Don)

350 heads, ported
083 iron L98 head: 200 int; 139 exh (smithtc, stock valves)
083 iron L98 head: 206 int; 144 exh (smithtc, stock valves)
083 iron L98 head: 203 int; 171 exh (smithtc, 2.02/1.60 Manley)
083 iron L98 head: 229 int; 171 exh (rhuarc30, 2.02/1.60)
113 alum L98 head: 210 int; 172 exh (Vizard stock valves, backcut)
113 alum L98 head: 224 int; 177 exh (Vizard, 2.00/1.55 valves)
193 iron L05 head: 196 int; 183 exh (Dyno Don, stock valves)
193 iron L05 head: 224 int; 216 exh (Fast355, stock size valves, backcut)
---

The 193 casting heads are not nearly as bad as the ignorant and misinformed of TGO like to think they are. The 083 heads are likewise not as great as many of those same people like to think they are. That's what the measurements show -- period. There is also limited track data, and dyno data, available on the above. So the head flow argument has no merit, as proven by TGO members.

The manifold-vs-manifold test, as done by Dyno Don, showed that the stock GM TPI makes roughly 7% more power than a stock GM TBI. The original L98 (Fcar) TPI made approx 10% more power than the 9C1 LO5 TBI engine (230 vs 205 hp) --- data consistent with Dyno Don's comparison. So the (9C1) LO5 had reduced airflow (and GM power rating) purely because of the airflow through the intake --- the cam can't be blamed because it was the same cam as L98; the heads can't be blamed because the 083 iron heads aren't much better in the intake side and they are arguably worse on the exhaust than the 193 iron heads, per the above table and TGO member data.

The intake flow can't be utilized unless the exhaust can clear out the cylinder, so don't be fooled in thinking that a marginally better intake on the 083 heads proves anything. Any head hampered by a poor exhaust has a built-in EGR. The LO5 has less power than the L98 because of the intake on the TPI is better than on the TBI.... and I can think of many worse 350 engines built earlier in the smog-era than the LO5.

If you believe none of this -- go read the original posts by the other TGO members that posted them.

Finally -- for Fat Kid -- I should have added in my last post that if I were doing it, I would use the TPI. The TPI is the best intake system for torque that GM never installed in a truck. You don't need big airflow nor power. A heavy truck is never going to be as quick as a 3500 lb Camaro anyway and you own the truck + the TPI --- so install the TPI and enjoy the looks of it under the hood and the awesome torque. Read the threads on doing the swap, so you have everything you need. HTH.

dimented24x7

iTrader: (2)

Which one of those heads is better, agian?

178 CFM at the intake is awful. As far as porting goes, thats a whole 'nother story. Im sure I could take a set of L05 heads and CNC the hell out of them and get 280 cfm, but that still wouldnt change the fact that theyre the worst flowing stock head around. The big advantage to the L98 head is that it doesnt have that big blob of cast iron in the intake that obstructs flow and would be a pain to grind out of the intake port.

kdrolt

You included the alum L98 heads (which have a different exh port) and you conveniently left out the other iron L98 heads. Here are all four as I posted them:

083 iron L98 head: 185 intake; 106 exh (smithtc)
083 iron L98 head: 194 intake; 118 exh (rhuarc30)
083 iron L98 head: 202 intake; 141 exh (F-BIRD88)
193 iron LO5 head: 178 intake; 146 exh (Dyno Don)



A brilliant deduction. Picking at the intake flow alone doesn't help, because the 083 heads have their own warts in stock form. And using intake flow alone is an incomplete means to evaluate the head.

Look at those exhaust figures on the 083 heads. The spread on them is incredibly large, but even if you take the median (118 cfm) or the mean (122 cfm), the exh flow is still terrible. The key point you overlooked is: how useful is good intake flow if the exhaust is poor? I asked that in a different thread and the engr student that replied basically punted on the answer. You can't assess the goodness of a head based on the intake alone, because if the exhaust doesn't clear the cylinder from combustion, then the next intake stroke can't be fully used. That fact should be obvious, especially to a mech engr student.

"Worst flowing stock head around" --- if the 193 heads are so bad, then why is the comparison between the L98 and 9C1 LO5 so close? If the 193 heads are so bad (which means you have to be basing it on intake flow), the how can the L98 heads be better given that their larger intake flow is severely constricted by the poor exhaust?

I made an argument, here and above in this thread, that the 193 heads are not nearly as bad as many TGO people believe. Here I argued that they really aren't any better than the 083 iron heads. I used data/facts to support the argument. I haven't even mentioned the benefit of the extra swirl the 193 heads have over the 083, and that matters too (see Vizard on cylinder head porting).

If I made sweeping statements about using a MAF on a TBI system (your thread btw), that it's a stupid idea because TBI is a turd, then I would be doing exactly what you are doing: drawing a conclusion based on a personal bias, especially in the face of measured data and engineering/science argument. If you have an argument to make, please do it with facts.

As far as porting is concerned, neither Fast355 nor Dyno Don removed the iron blob and yet they still got decent/great intake flow numbers. In both cases the exhaust flow is good/excellent which means that the intake flow is not constricted by a weak exhaust. When I last checked, neither used CNC equipment and neither are professional head porters. 280 cfm would be of little use to either a TBI or TPI engine, as you already know. If the 193 heads were that bad, due to the much maligned swirl ramp, then neither Fast355 nor Dyno Don should have gotten anywhere near the performance of the ported 083s because both smoothed the ramp but left it otherwise alone. The poor intake, good exhaust comment applies to the stock heads as well. The intake flow on the 193s is poor, but the exhaust is very good (for stock heads) so the intake flow is fully utilized. It is not fully utilized on the 083s. And that's why the 193 heads are not so far removed from the 083s. The TPI makes better numbers, in stock form, than the TBI because of the intake manfold, not because of the heads.

The fact that Dyno Don's test on TBI-TPI intakes even on a 305 shows enough of a percent difference for peak power to explain the power differences between the 350 L98 Fcar and LO5 9C1 Bcar engines, then there is no further merit is saying that the heads are the problem. The intake manifold dyno data, of Dyno Don, shows that even on a 305, there is at least a 7% difference that favors the TPI. So if we took a L98 Fcar engine and yanked the TPI and replaced it with a TBI, leaving the heads/block/cam alone then we should expect at least 7% loss in peak power. Using exactly 7% loss, the 230 fwhp L98 would then peak at 214 fwhp. If we reduced the timing to 0deg base, which is what the LO5 used IIRC to run on 87 octane, then I wouldn't be surprised to see the power drop to below 210 fwhp. The LO5 was rated at 205 fwhp. That's basically a wash.

If the 193 heads were really that bad, as compared to the 083 heads, this comparison made here wouldn't even be close and I never would have posted any of this. I have no affection for either head design, nor for the intake designs (well -- TPI does look cool). Anyway, the head comparison is more than close. Both the 083 heads and the 193 heads have flaws. On the 193 heads, it's the poor intake flow. On the 083 heads, it's a very poor exhaust flow. Both can be fixed by porting. I included both the stock and ported data, so that I wouldn't be accused of hiding anything just to support my own views. The data by ThirdGen members shows that both 193 and 083 heads can be ported to levels equal to, and in some cases better than, the L31 Vortec heads. Problems from both heads can be avoided entirely by using modern and costly AFR heads. Or buying a new Vette. But the AFR heads, or new Vette, don't address the head flow issue, nor the intake manifold flow issue, on ThirdGen cars built 15+ years ago. And the new heads/Vette don't help someone trying to improve the performance of their 3rdgen car especially on a budget.

So my discussion was aimed entirely at linking Dyno Don's work on TBI-TPI intake manifold comparisons, and on the head flow numbers (especially 083 and 193 castings) made by various 3rdgen members. The link among all of them has not been done here before, until this thread and the one on the 193 casting by Fast355 on the TBI forum. If you have some useful technical argument to make, please do so. We already know your opinion so you don't need to remind us again.

dimented24x7

iTrader: (2)

As far as the 193 heads, the simple fact is that most of us dont have trailer hitches on the back of our cars, so we'd at least like to have a prayer of making something reasonable in the line of power. 178 CFM implies that there will be a good deal of pressure loss in the cylinders of any engine that tries to rev past 4k with those heads. They might be ok for towing or in HD vehicles, but they really have no place in anything set up to make power. Even in truck applications, jsut about any small runner head like the vortecs or some aftermarket head that flows above 210 CFM or so will open up a 6-pack of whoop-*** on those heads in any application. They where a neat idea and they worked for the the application that they where intended for, but they have little power potential in stock form. Sure, you could make 250-275 HP with them, but just imagine how much a better flowing head with an equal sized runner would make.

As far as the exhaust port goes, all stock SBC heads flow like crap at the exhaust, but with those heads that wont matter much as the cylinders wont really fill to begin with. The flow at the intake is even more critical as there is only 14.7 psi of atm. pressure to force the air into the cylinder. If the air/fuel cant get in there, the engine simpy isnt going to make much power. With the exhaust, the engine can at least use some of its power to force the exhaust to flow out of itself. If you think this will cripple a motor, take a look at teh vortecs. Not perfect, but people have run very good times with them even though they flow like poo at the exhaust port. With the intake, if it doesnt allow the cylinder to fill fully theres no hope of making much power to begin with.

As far as a stock tbi system being a turd, it is. Id never use it on anything but a stock L03. But, however, like tpi, with some mods it can be melded into a unique system that can be suited to any users taste.

With those heads, you can grind away at them untill doomsday to clean up the intake and exhaust, do any machine work needed to them, upgrade the springs, etc. to accomodate a reasonable high lift cam, or you can accomplish the same thing with less effort by just buying a decent set of stock or aftermarket heads to begin with. IMO its misinformation to say that theyre a good head for performance use. Maybe for towing, but theyd be pretty low on my list if I wanted my engine to at least have a prayer of making power. Can they be made to make power, sure, anything can, but its easier to start with a good head to begin with.

kdrolt

That line of reasoning is similar to: if you can't argue the facts of the case, then argue about the law.

I was refering to what the engine can put out, in stock or ported form, based on the heads (083 vs 193) and the intake (TPI or TBI). You are talking about trailer hitches and implying that vehicle weight has anything to do with it. It doesn't. That GM intended the 193 heads for fullsize sedans and light trucks doesn't preclude it from having power potential. More modern GM examples: L31 Vortec heads, LSx-family truck heads.



That's another conclusion based on no evidence -- just opinion.

http://www.chevyhiperformance.com/te...98/index4.html

Vortec L31 heads, peak values: 239 cfm int, 162 cfm exh

Let's see, that outflows both the (stock) 083 and (stock) 193 heads by 10 to 30% on the exhaust, and by a lot more (stock) on the intake. So it's no big surprise on the whoop-***. And the L31 heads are designed for lightweight C/K trucks, which are heavy compared to the Fcars. Do they also have no place on lightweight cars as well? You introduced weight into this discussion, and you are resting part of your argument on it.



A handy conclusion since you completely ducked the 083 stock head flow data, and after having ignored the effects of TPI-TBI manifold on airflow.



I don't have to imagine. I already said that the problem(s) of both heads can be solved with AFR or equivalent. i.e. money can solve the problem. This is also not a surprise to anyone reading this post, so you aren't offering anything new.



When the 083s only flow in the 120 cfm range, then they are not using all the 180-190 cfm available on the intake. They are more imbalanced in stock form; the lack of a good exhaust inhibits the good intake numbers. On the 193s the opposite is true, so the 193 in some respects is better balanced because it probably CAN use all of it's (feeble) intake flow. But on the whole, both heads are flawed and that's what the data (so far) shows.



Now your logic, if any, is really failing. If the engine uses it's own power to force the exhaust out, the power of the engine is reduced. i.e. BSFC goes up. And as I keep saying, over and over, there are two parts to this: the intake has to flow well to make torque and power, AND the exhaust has to flow well enough to flush the cylinder from the prior combustion event. Ideally you want both to perform well. The 083 does a better job on the intake; the 193 does a better job on the exhaust. Viewed as a system, neither are stellar performers and both perform similarly (albeit poorly --- but they're stock heads from 15+ years ago). That's what the head flow numbers show, and the dyno data (Dyno Don, GM) are consistent with that conclusion. The intake manifold choice (TPI vs TBI) has more of an effect on the engine output in stock form than the heads do. Q.E.D.



I already quoted the Vortec head flow data --- it's much better than the 083 and also better than the 193. The L31 heads flow extremely well on the intake, and the exhaust is still very good even in stock form, so the total system runs well. That's where the power comes from, along with the swirl induced by the chamber shape and the projected nose of the spark plug into the chamber.

Another L31 data point. Dyno Don started with an L31 block, and added stock unported 193 heads and an Fcar LT1 cam and a factory TPI. It made 210 rwhp into what ever (unknown) exhaust he had on the car. That's 240 to 250 fwhp depending on your choice of a fudge factor for the T5 trans he was using. The Fcar LT1 (which has the same chamber/port casting as the L31) was rated at 275 fwhp. So clearly something was limiting the output power compared to the L31/LT1 heads and the LT1 intake, because he only reached 89% of the output power of the Fcar LT1. That means 11% power (and airflow) is missing.

Q. What's responsible for the missing 11%, the use of the TPI intake vs the LT1 intake, or the use of the 193 heads vs the L31/LT1 heads?

If you say that the heads are responsible, then the effective pumping of those stock 193 heads should only be down by 11% on power as compared to the stock Fcar LT1 heads. Those numbers appear here too. CHP got 215 cfm on the intake and 171 cfm on the exhaust. Comparing the intake for the 193 to the Fcar LT1 is 178/215, or 83%. On the exhaust it's 146/171 it's 85%. I don't know if Dyno Don flow benched with a exh pipe extension so assuming he didn't, then the exh ratio of 193 head to Fcar LT1 head would be 146/154 or 95%. IOW the exh flow is close, so it's sensible to assume that the 193 heads were limiting the intake flow, but not 18% worth. Only 11% based on power.

Of course, if you say the TPI intake is responsible for the 11% loss as compared to the heads that that would mean the heads are not a restriction relative to the TPI intake.

Then Don ported the 193 heads and repeated the test: 250 rwhp (294 fwhp, again using 15% loss), and ran 13.7 @ 101 mph. The point in all of this is that the 193 heads can be used for some level of street performance, especially for the budget-minded, as demonstrated by other ThirdGen members. Can you do better by porting 083 iron heads from an Fcar L98? Maybe, but the data so far suggests that the 193 heads will do as well for the novice porter.

And your post, dimented24x7, along with others show just how stubborn TGO members are to changing their views in spite of measurements, dyno data, and track data from other TGO members.



I used that description to illustrate how narrow-minded I would be if I made that blanket statement, with no consideration for the engineering & science you put into the job. IOW if I dismissed it just because I didn't like it, or someone here told me it was a stupid idea, or that it was a stupid idea because it doesn't look good for performance, even if you had data to support that it was a decent idea given the limits of what you were working with (TBI, 2 injectors, airflow limits in 2 bores).

IIRC we have had people here that have said "swirl port castings are junk -- everyone knows that." I don't. I can see the ramp in the port, I know why it was put there, and now (recently) we have flow data on the 193 swirl port heads to compare with the 083 heads. The 083 heads are better on the intake, and worse on the exhaust compared to the 193s. The power output for the engines is similar, so long as they use the same cam (L98 Fcar vs LO5 using in the 9C1), and after considering that the TPI outflows the TBI. If the power outputs are similar, after taking the intake into account, then how is it that one head (083) is so much better than the other (193)? The answer is that one isn't better from a intake-exhaust system view. They are both flawed. Both can be used in stock form for similar levels of slight performance gain; both can be made to flow MUCH better after porting. I'll leave aside the argument for which is better after porting. And the heads, both 083 and 193, can be replaced with more modern, better flowing, and more expensive heads. There really isn't anyone here that doesn't know that.



Great. We agree on something. Go back and READ where I've said that several times. Money will solve all the head flow, or intake flow, problems. Hell, buy a new car instead. That's no surprise to anyone here, but it also offers no insight into the 083 vs 193 comparison.

And there you have it ---- readers judge for yourselves. dimented24x7 says that it's misinformation to say that the 193 swirl port heads, even after a doomsday's worth of porting, are a good head for any kind of performance use. I don't agree with him at all.

The 193 heads are arguably no better, in stock form, than the stock iron 083 heads (which are often used for budget street performance). The 083s flow better on the intake but they flow poorly on the exhaust; the 193s have almost the same averaged numbers but they flow better on the exhaust side. The 193s are, at the very least, the equal of the 083 heads after porting even by the novice. For the budget minded looking for a performance gain, either 083 or 193 castings can be used because good results can be had by both heads. I'm not making those claims based on handwaving or hearsay or from just looking at them, I'm basing my comments entirely on the flow data, dyno data, and track data of the TG people I cited previously.

dimented24x7

iTrader: (2)

believe as you wish...

kdrolt

Agreed.

Low C1500

As posted aready, I don't think a TPI swap is worth it. Mod your TBI to get the extra power.

If you want some bigger power go to a carb, or for more effiecent big power to a Stealth ram intake (or similar, with the TPI computer).

Fat Kid

well, say i stick with tpi for a while, then go to stealth ram. i hear SD makes it harder to mod the engine? what if i wanted new heads, or a cam? how difficult is it to do with a SD computer? i have tunercat...maybe i could get a bin from someone with a modded motor like mine (hypothetically)?

thanks

five7kid

iTrader: (14)

SD makes it easier to get to most out of such changes. The PROM forum is the place to hang around to get more info about that.