Hi there everyone,
I have a question on the amount of power a stock TPI induction system can make on a flat top 383 motor with stock L98 heads, stock computer, stock 19LBS injectors & a Comp cam XR264HR-12 (264/270 212/218@.050 .487/.495?

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86 Tramaro 90% Trans Am/ 10% IROC/Z (nose, hood,& fenders)
Trans Am Mods as of 1/10/01
3inch
T.E.S/Flowmaster setup,gutted cat,gutted maf,relocated mat,373 gears,upgraded factory chip,255 lph walpro f/pump & throttle body coolant bypass
njdaewoo@excite.com
New mods as of 6/10/01:
383sb engine
Comp Cam Xteme XR264hr-12
smog pump by-pass

 

I dunno, but after all the expense of building a stroker, why not work on the intake?

 

Why in the world would you be using 19 lb. injectors on that motor? I'm not sure it will matter how much you port the intake if you don't have any fuel going in.

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91 TA 5.7 TPI Automatic
w/WS6 and 3.23 rear.
K&N Cone Air Filter (at the end of the plastic tube), Hypertech Coil, Moroso Blue Max Wires, Bosch Platinum plugs, JET 180*fan switch, JET air foil, Dual cats with Flowmaster 3" cat-back, GM Performance PROM, Complete PST components on front suspension, Spohn LCAs/Panhard bar.
My car only uses Mobil 1 synthetic fluids.

 

Im using the 19lbs injectors for now because in 2002 I'll be installing AFR heads & while I have the intake off anyways I will change them then. My car, for now, has been stored for the winter so I dont have to worry about a severe lean out. Once I buy those heads I want to know what size injectors to buy. For 2003 I'm planning on buying a ATI supercharger so is there a in between injector that I can buy to satisfy my needs or do I have to buy 2 sets of injectors?

 

Why not just save yourself some money and time and put a carb setup on it? I will bet a thousand large it will make more power with a 750cfm carb and a decent intake than any ported out tpi setup. The low end torque tpi creates will make it a pain in the @ss to launch too.

Sometimes low-tech is better...and much cheaper

 

You better check your compression ratio: With flat top pistons and L98 heads, I'd bet you see 10.5:1 or more with the 64cc heads.

Since the L98 is a sub-5000 RPM induction system with a 350 block, you'll run into similar breathing & induction tuning issues. Therefore, your cam is probably as BIG as you'll want to go.

I'd say you will want to put in 21 pound injectors and crank up the fuel pressure to 42 to 45 PSI, and keep the revs below 5K. The 19's are pretty small-ish for that size engine.

You are going to be intake limited to approx. 325 HP, I'd say. Still, that's low 13's with good traction...

 

Unless you are going to change the intake and heads, you are wasting your time with the cam. The cam will sacrifice low end TQ for high rpm HP, but you don't have the intake or heads to let the engine breathe. So you will end up with less TQ and no extra HP.

To get the most out of TPI, you need heads, intake and cam to match (with a proper eprom). The cam is the cheapest thing to replace. I would go for the intake and heads first and change the cam to match later. You may find that when you decide upon the intake/head combo that the cam you are planning to use is not a good match.

 

I was kinda wondering the same thing about the TPI set-up, I have a 383 that is almost done, and I am still running the stock heads and intake with the same cam you are using, but my heads and intake are all being gasket match ported. . . will this give me a better yeild than the 325 intake limited horsepower you were just talking about?? also, will I be able to make more high end horsepower cuz of the porting?? I already have 22lb injectors, and I am going to get an AFPR. I plan on doing tons more to the car, definately get a better intake by the end of the summer. . . what do U think for now??

 

What about that adapter that allows a converted carb intake (injectors & fuel rail installed on carb manifold) to be used in place of the restricted TPI setup? Does anyone know if this would make decent power (400 - 500 hp) without having the top end flow restriction.

 

Now youre talking!

A converted carb intake would be ideal (if you MUST have efi) but like I said earlier it would be loads cheaper and just as effective to just get a carb. I have never done one of these conversions, but I can imagine that it would present some computer issues. I personaly like the idea of ditching the computer, for ease of repair/installation/adjustment. You gotta think to yourself which is better? 80's computer technology or 60's carb technology. Emmisions could be a problem, but from my experience it is easier to adjust a carb and get it to pass than mess with a computer.

I think you are on the right track. For your own good, DO NOT PUT TPI ON A 383! You WILL choke your engine. You may want to look into a GM ramjet setup. It will definetly support a built 383. The only downside is that I think you need a cowl hood for it to clear.

Keep looking at everything before you make up you mind and buy something.

Good luck

 

Keep your TPI, go with 24 pound injectors, a 52mm throttle body, a SDPC Vortech TPI intake, and a set of GM Fastburn heads. Roll in a hydraulic roller cam such as the ZZ4 or the HOT cam, and see what happens. Re-tune your ECM and you'll have LOADS of fun.

 

Call Lingenfelter engineering. Back in '89 they built a high-12 second 383 TPI car for a magazine shoot-out (Car Craft(?) - "Twelve Ways to go Fast"). They ported the plenum and base, as well as modified the MAF. It had a single Cat and stock air tract. It also used large tube runners, SLP headers, and a Borla Cat-Back. They are currently selling 383 shortblocks to replace L98 350s. I think they can match your parts for you.

 

I was reading a Hot Rod from '86 the other day where they built a 383 tpi. The best N/A run they could get after the 383 was installed was 15.0! Sure when they sprayed it ran high 12's, but they only gained .2 sec compared to the stock LB9. Their tpi system was 100% stock so I wouldnt think their results are typical, but it just shows you how restrictive the tpi system really is. LTR setups can be made very fast, but in general you'll end up with more low end torque than you know what to do with (breaking stuff/poor launches) and no top end power. The system works great for making 305's fairly strong, but remember that is what the system was designed for...not 383's.

Just thought of something...why not try John's LT1 intake conversion? That would be cheap and work well on a 383!

 

I ported & polished a stock TPI base, added SLP runners, and a 52mm throttle body, and sold it to Bill Davis. His '86 Camaro Z28, with original 305 is now running this modified stocker (with different cam) to the tune of 14.1 seconds and 98 MPH. I think that if Hot Rod couldnt break into the 14's with their TPI (when even some stock L98's can) then they simply missed something in their build up. Like, perhaps, tuning??

 

Still,
14.1 with a 383?!?!
Come on now that should be capable of much more, which is what I was saying. It would be cheaper and faster with a carb.

Period

 

The authors also said they had hooking up. E.t.s don't rely soley on the engine h.p. I remember that article well. When they got it to bite they cracked their windshield. I think people expect too much from 383s - they're not that big of a motor! You need the right combo of engine and gearing.

 

The article said they had trouble hooking up, but that doesnt explain the jump to the mid 12's with the addition of nitrous. That could be explained by saying the intake wasn't flowing well enough. There are many people running 14.2's on stock L98's. 13's are not uncommon for engines that have only bolt ons. I dont think I am expecting too much from the engine. When they (383's) are built correctly they can power your car into the low 12's high 11's easily. If I wanted to run 14's, I would build a 305 not a 383. I think 86ta/maro is expecting faster than low 14's as he/she should.

 

well I am going to be running a ported lower intake, and eventual, (this spring) definately go with better runners and possibly also a better upper intake. I already have SLP short tube headers, and a full 3 inch header-back single cat exhaust. . . . so I guess on the other side of the combustion chamber I am pretty well set up, not all I need to do is throw a better intake on it. I definately want to stay fuel in jected though. what to do??

 

yes, I do expect a lot more out of a 383 combination than14.1! No , I dont want to go the carb route because I've been there & done that before. U cant beat the driveability of a fuel injected car! When I had the stock tpi 305 in there with edelcrap headers, flow master 3in cat back , 3.73 gears & all the free mods. That set up felt really impressive with it's 13.92 @98 mph in the quater. Now, since i've changed the motor. the car seems strong on take off & midrange but, dies out at about 4300rpm WTF! When everything is said & done I want my car to be in the 11s after my blower install. Any comments?

 

The TPI was designed for use on a 305 UP TO 4800 RPM. Now guess how that's gonna work on a 383.

 

Does anyone know what he's asking???? The answer is, with a stock TPI, don't expect too much. Why the heck is he asking this if he's putting a blower on the damn thing?

 

Absolutely. That article gives testimony to a STOCK TPI induction system. It is a "what-not-to-do" guide (keep in mind the technology and availability of aftermarket parts at the time, however).

p.s. Every month in "Muscle Car Review" they give the e.t.s of 60's and early 70's factory stock musclecars. Most are in the 15s, just like the 383 Camaro in the article. It's stop-light to stop-light times that count on the street.

 

LOL i like the blower comment , for got to add that. i'm building a 383 also, i ported the upper and lower intakes, and also the runners . i have the cold air mod and most of the other free basics, i have a 3" cat back exhaust (all on the current 305), and will be porting the heads (similar 462 castings) also, with major attention to the exhaust side. i want to try the setup with everything as it sits right now, and see what happens (buying a g tech to have something to compair with) . it should be pretty good but i want to see just what can be done with the tpi setup and maybe 22lb/hr injectors. if lingenfelter and others can make good power in 383's and 350's with a stock but mildly modified intake setup, i think money can be better spent elseware ($1200 for the "killer" intake setup worth 22-30 hp HP tells me the intake isnt so much the limiting factor) . didnt someone do a 502 buildup with the 48mm TB and the stock (ported) plenum? if i recall that motor made great power and torque with the little TB , so that should say something also. just my .02

 

86ta/maro
The problem of the engine running out of steam at 4300rpm is because you are using a tpi setup. If I were you I'd look into the LT1 intake conversion. That would be the cheapest, best way to get performance out of a efi 383. There is a tech article here at John's page.

http://members.home.net/millicanga/s...into_a_1st.htm

Or you can shoot him an email and he will do all the necessary modifications for you (for a price). The intake can be purchased on ebay fairly cheap.

Or if you are loaded and need to spend some cash, get a miniram .

 

That is incorrect. The problem is a 383 TPI intake will not flow the air necessary to make power past 4,500 rpm. You need more air flow to make useful power beyond 4,500 rpm and the TPI is NOT going to do it. You will end up with a HP line flatter than Kansas after 4,500 rpm.

While, if you went to a "freer flowing" intake like a Miniram or modified LT1 intake, it will continue to make power upto 6,500 rpm (depending on your heads and cam). The difference is FAR greater than 22 HP. Probably more like a 100 HP, again, depending on the heads and cam.

The great thing about a 383, is the long stroke more than compensates for the loss of TQ from a TPI 350 to a Miniram 383 - again, a proper choice of heads and cam can further compensate.

Sorry, but a 383 TPI is a dandy "truck motor" to haul your boat out of the water, but it will not make HP and or produce extra power past 4,500 rpm. You need a better flowing intake.

 

i do agree, that 4800-5000 seems to be the top end for tpi's . i was talking more about power over the entire band. and yes i agree that the better intake systems make more power , just not justifiable for the price for me. in super chevy this month they did a comparison with the scroggin dicky vortech intake. with the stock plenum and TB,zz4 cam and lt 4 springs (about $750 over stock), compaired to the same engine with edelbrock runners and TB, gm performance hot cam and 1.6 roller rockers (about another $1100 in parts) . the PK #'s were at almost the same rpm's (due to the charistics of the efi set up) but they only made 28 ft/lbs and 37 HP more. for me, i would like to shift at around 5500 rpm's (pk around 5200) and have my PK TQ around 3500-3800. which should work about perfect with the tpi set up. it should be a great street motor thats usable and pretty cheap to build also (due to the low rpm's). but yes you are right about the top end , i just think you can make more power for the money in the rpm band thats used the most 1500-5500.