66impalaTPI

I wanted to know how much rear wheel horsepower I can get out of this engine without changing anything internally. Does anyone have dyno numbers? Any numbers at all?

leeperryracing

if you're only doing external mods...I would guess anywhere between 220-240 and that's if you get the tuning dead on.

66impalaTPI

220-240 rear wheel horsepower, just external mods? That seems really low. Does this include headers with exhaust cut outs and a fully ported intake manifold, runners, and plenum? Does anyone have this setup without changing anything internally?

leeperryracing

if you add all those you will get some more hp but remember the best year for the iroc was '89 when it made 240hp brand new and you said yours is '87 350 tpi which i think was rated lower than 240..thats 17years ago and the thousands of miles they racked up over the years induced a lot of wear and tear which always significantly reduce hp and torque numbers on these engines...my point is that worn out internals is gonna put a limit on how much power you can squeeze out of it and this is not only for tpi motors.

3.8TransAM

91 GTA 50k miles

24# injectors and SLP catback are the only mechanical mods.

I do my own tuning.

225hp and 315ft lb torque.

later
Jeremy

leeperryracing

thats nice, but an average '87tpi motor has more like 150,000miles.

nidyanazo

Is that 240hp at the crank? So factor in ~18% driveline loss too.

leeperryracing

good point..i didn't even remember drivetrain loss!

DJP87Z28

The Stock 87 350 TPI was rated at 225 HP at the crank and with a Auto 20/22% drivetrain loss you would have about 177 RWHP.
Without changing the Cam I don't see very much improvement over those Stock bunbers.

Orr89RocZ

iTrader: (20)

full bolt-ons

like intake, heads, 1.6 rockers, CAI, full exhaust i would think you can get 240-250rwhp easy. Thats 300-312 horses on motor with 20%loss. your cam will be holding you back from there.

like a stealth ram with AFR 195's and longtubes with free flowing exhaust. If the tune is real good, should make some good power if the motor is good condition internally and didnt lose any compression over the years.


now, the fun part. do all the above and add nitrous 125-150 shot and see what happens. could get 400hp or more but who knows how long internals will last under that abuse. LOL

DJP87Z28

For the Mods suggested in the above Post by Orr89RoZ to the Stock 350 TPI, I would just go ahead and change the Cam and get the same results easier and cheaper.

Orr89RocZ

iTrader: (20)

true, just a cam swap on 350 TPI would yield good results. probly equal to my previous post. good point, and ofcourse if you go as far as intake and heads, your gonna get a cam as well unless your after some kinda record or something with stock shortblock. LOL

66impalaTPI

I have 200,000 thousand miles on my motor. The motor is running really strong because I cruise most of the time ,but The only time I would actually beat the crap out of the motor is when I do highway roll on's. I had the car on the dyno machine and it pulled 206 rwhp and 306 ft of torque. I have a custom cold air intake, x-pipe, 58mm Throttle Body, and 3.73 gears. The numbers that I am seeing from you guys scares me a little bit because I thought these motors would have put out a lot more horsepower than 240 rwhp.

DJP87Z28

All numbers from the Factory are at the Crank and are not RWHP. the quoted 240 was tops for a 350TPI in 89 model and its at the crank.

Orr89RocZ

iTrader: (20)

yeah, TPI intake is the thing that holds back HP production. lots of restrictions in the airbox, intake/runners, and exhaust. Replace all that and you will see good gains on the 350+ motors for sure. TPI was a 305 intake and doesnt flow enough to support lots of hp since it only makes power to 4500rpms.

you may only see like 20rwhp from alot of bolt ons, but look at the torque output. thats what you get from TPI is torque. They love it and so do I. LOL

and that 89 350 power numbers were for the dual cat converter cars which probly made abit less than the dual cat speed density 90-92 cars.

WinnipegGTA

Wow those are some impressive stock RWHP numbers
Thats what like 270/370 at the the crank? Can i borrow that Prom?

kevinz85

I thought the 90-92 made 245 from the factory.

nick418

true it is.. But on the Firebird L98s they made 5-10 less hp then the 245 hp Camaro due to the intake design