Alright, April 18th I'm gonna be putting in my new GM performance 350, TCI transmission, B&M Holeshot 3000 T/C and full exhaust.
The motor is a GM high performance 300HP /370 ft. lbs 350. I'm gonna be using fulling ported TPI intake on the motor because it peaks at 5000 rpm. I'm expecting a minor HP gain and a huge gain in torque. so maybe 310HP/390ft.lbs to stay conservative. Also have SLP 1 3/4" headers, Hooker Catback with aerochamber muffler and dual exits. Maybe another 10 HP gain out of that. I'm running A/C delete, but all emissions equipment (ordinance mandated) coupled with a 3000 stall and stock 3.27 rear and some Nitto drag radials I'd like to know what this setup can get me. I might get an AFPR and set it to 50 psi if necessary, although probably isn't. I'd like to know what E/T I could get. I'm a good driver, pulled off a few 14.6-14.8 second runs with my car bone stock, so I'm sure this new motor won't be that hard. I predicted a mid 13 second run with this motor, transmission, and stall with everything tuned properly, do you guys think this is accurate? What are other 300-320 HP 3rd gens around here running?

 

That motor is "rated" with an intake system that flows, and that doesn't have TPI's anti-RPM features. I doubt you'll see 300 HP out of it as long as those long runners are on there, you may get close though.

For comparison purposes, a ZZ4 is "rated" at 345 HP; but the same motor with TPI and the cam for it is "rated" at 240 HP when it's a L98 in a Vette. That should give you an idea of how much HP TPI will shave off of an otherwise strong-running motor.

That stall and gear are a good match for the rest of the combo. It should leave hard. I'd guess you should be able to get low 14s, maybe 14.2-14.3, at right close to 100 MPH out of it.

 

this motor peaks at 5000 rpm though, it isn't a ZZ4 motor, I don't think TPI will be even close to restrictive at 5000, that's square in it's operating range. I don't get why TPI would reduce HP when it makes far more power than carbs do on 5000 rpm or less motors I'm also using 1 3/4" headers and full 3" catback, people are saying that'd get .2-.3 seconds off the E/T. I run about a 14.4 now with stock stall, manifolds, and a flowmaster catback. I'm not gonna even bother with this motor it's not gonna be making at least 290 H, **** I could get low 14s with headers and stall alone, might even scrape 13s with the L98. I'd hope this would be much stronger than that with all this stuff. What would be a better emissions legal system to use on it then if TPI is gonna choke out 50 HP... I keep getting confused. Here a lot. People always say "oh TPI is great for motors to 5200 rpm, you'll get better results with stock TPI than you would with a stealth ram or mini ram which claim 40-100 HP gains over stock TPI at the same RPM, you'll just end up losing torque etc, but then I hear that a TPI unit is too restrictive, it will just choke out your motor even at the same RPM, etc. etc. I can see for a motor peaking at 5500+ rpm, TPI just won't cut it, but how can a ZZ4 rated at 345 HP, lose almost 100 HP due to TPI when TPI adds 50 HP on a 305 over a 305 carb'd (LG4 compared to LB9)??? I mean, the carb has gotta be absolute crap when compared to a properly tuned fuel injection intake. It's puzzling, I know TPI is restrictive, but I thought it was only at upper RPMs. It makes a buttload of torque and flows well enough at 5000 rpm when ported out. I dunno, this is just not adding up. I need a scientific explaination for this...

 

http://www.goautocenter.com/300hp_tpi_1987-89.htm
that is the Motor btw ^

 

TPI is "Tuned Port Injection". The "tuned" part refers to its design feature whereby the positive pressure pulse in the intake tract that is created when the inrushing air down a runner slams into the back of the intake valve as it closes; the runners are of such a length that at a certain RPM this pulse (travelling of course at the speed of sound) reaches the next cylinder that's filling and reinforces its filling action. That RPM happens to be 3600, more or less (dependiong on the temperature and a few other variables). That's why TPI has that nice torque peak at 3600 RPM. But as we all know, there's no such thing as a free lunch; the penalty is, as RPMs increase, eventually the negative acoustic pressure pulse that precedes the positive one, reaches the next cylinder just as it's filling instead of the positive one, reducing cylinder fill in that RPM range. This "de-inforcement" peak occurs at around 4500 RPM. Then at any RPM higher than that, the simple restrictiveness of a 22" long runner that's only 1¼" or so in diameter takes over, and it's just not possible for the engine to move air fast enough down it.

So as long as you put TPI on it, that motor isn't going to peak at 5000 RPM, no matter what it does when some other induction is on it.

For a more apples-to-apples comparison of 305s, compare the L69 to the LB9, instead of the LG4. There you have a weenie stock intake manifold and a Q-Jet making 190 HP "rated", using the same exhaust and a similar cam, instead of the grossly inferior pieces in the LG4; the TPI 305 was "rated" at 205 HP when it was introduced, and the cars weren't any faster than L69 cars had been. I had no trouble whatsoever smoking the automatic 305 TPI cars, and still ran about even with the 5-speed ones.

I accept no responsibility for the numbers, I didn't make them up. I only report them. It's really not my fault that a ZZ4, which is a flat-top 350 with a certain head casting, makes 345 HP with a carb, and the L98, which is another flat-top 350 using the exact same heads by part number, made 240 HP. TPI was not my idea I assure you. I was completely underwhelmed by it the very first time I exposed myself to it, in 1985... that's why I still drive a 83 L69 car. While I have nothing at all against fuel injection, in fact I'd love to have it, I'm not the slightest bit interested in TPI. I'll put a MiniRam or an Accel ProRam on my car, or leave it carbed.

But don't believe me, and don't take my word for it. Spend your money how you want and do what you think best, and come back and let us all know how it went. Look at all the signatures of people who have worked-up L98s and look at their times, and think carefully about how what you're going to do will end up differently from all of them that have done pretty much the same thing. Good luck.

 

I don't think the L69 is a fair comparison, didn't all the cars they powered come with 5-speeds and 3.73 gears? Anyways, what about aftermarket options like long tube/large tube or siamesed runners, and ported baseplates and plenums? won't these help increase air flow at higher RPMs? And that motor was designed for a TPI intake, so wouldn't it work best with it? If I can't get past 240 HP with a TPI motor how are there several 300+ HP 350s with TPI? I'm not talking about a ZZ4 or similar engine, this is a completely different crate motor marketed as a TPI engine and equipped with a TPI baseplate from the factory. I think I need a less biased opinion no offense. As I said before, I could knock off 14.5 with a catback, I could probably pull a 14.0 with headers and a 3000 stall alone... It wouldn't make sense to me that a motor designed to operate within TPIs limits but make a few more horses wouldn't make more than 250 HP... Mini-Ram, Pro-Ram, modified LT1, and Stealth Ram units aren't emissions legal anyways, I don't think it will pass here when NOx emissions are way above normal due to EGR removal.

 

basically then, if I were to get a stealth ram and put it on my L98, which is basically a ZZ4, I could expect to see 340 HP with all the proper tuning then?

 

Yes. Easily.

The Stealth Ram is actually a certain old carbed "street tunnel ram" casting, that Holley had come out with years and years ago for street rodders... if memory serves correctly, it was supposed to use 2 390 CFM or 450 CFM 4-barrels. It didn't run worth a flip needless to say, not that iwas meant to; it was supposed to be a play-pretty for the street rod types, to hold lots of chrome and polished things way up high out of the hood or whatever. Well, they designed a new plenum for it, for a horizontal-draft TB, and cast some injector bungs in it, and volią.... instant port injection.

It will support up to about 425 HP before it runs out of flow. You probably won't get quite that much with it on of a 350, but it should be no problem to get 375 out of it.

It's not strictly emissions legal since it doesn't have an EGR passage. However, in most places you can still get by easily enough that way, with a cat installed; you can avoid the trouble codes by burning your own PROMs (which any serious FI tuner pretty much has to do anyway). A couple of people on this board have them, and have gotten pretty good results with them.

That motor wasn't "designed" for a TPI, any more than any other motor is. TPI is directly interchangeable onto practically any relatively late model SBC, and the only "design" feature the motor has to have, is an appropriate;y chosen cam... specigically, one that supports TPIs strong point, namely its 3600 RPM peak.

Aftermarket parts for it such as runners and bases definitely help out somewhat, but do not overcome the fundamental physical behavior of sticking a 22" long tube with a 180° bend in it in the intake tract. And they are $$expensive$$... far more so than alot of other approaches to the same thing.

TPI will support up to about 325 HP, with everything maximized, optimized, and correctly matched. The people who have achieved those numbers don't have some random relatively cheap off-the-shelf crate motor with a TPI just stuffed onto it; they have (usually) expensive heads such as AFRs, one of a very limited number of cam profiles (virtually always roller... unlike that one, which has basically one of the stock L98 cams in it), highly tweaked PROM tuning, higher compression than that motor has (usually 10½:1 or higher, with aluminum heads), etc. etc. Just because some people have gotten their TPI motors up to that level, doesn't mean that the motor in question will do that, once it has been installed in a chassis.

But again, don't just take my word for it. I'm not a fan of TPI at all; in fact I despise it, and consider it to be the single biggest reason for the failure of the F car in the marketplace. It created such a well-earned reputation for being such a dog for so long, that it allowed the competition (the Mustang) to run away with the prize (market share and profitability); and by the time GM fixed the problem with the LT1, it was already way too late. The battle was long since lost. Talk to people who have had some degree of success with it, who are relatively few and far between, and see what they really have, and how much time effort and money they have tied up in it, and then figure out if that's the way to go for you. I think you'll find, if you really want to get to 300 HP and beyond, there's lots of better ways of doing it... if your local emissions laws don't prevent it.