Im taking my Iroc into a shop monday to get the 305 tpi swapped out for a stock 350 tpi from a 91 formula. Along with this Im having the shop put on a set of hooker 2055's and a 3 inch flowmaster american thunder cat back system and there gonna just straight tube the cat. so i was just wondering with just these things what kind of horsepower do you estimate Ill be looking at? thanks.

 

Good running 350TPI with headers/catback... figure 220-230whp.

Same mods on my car but with 2800 stall on slicks with 3.42 gears it went 13.63 at 97. It would have dyno'd about 220-230whp Stealth ram intake and rocker arms dyno'd 254whp and went 13.2's at 101+ in similar air quality so it had abit more power.

 

I thought the 91 350 was rated like 240 hp stock though?

 

245 actually, but that's at the flywheel, with full exhaust and headers I think Orr's estimate is right.

 

so then with headers and stuff what would the engine be at then?

 

Around 260-270 if you add 15% drivetrain loss

 

240-ish stock at the crank is what they were rated at but I feel they were underated. MOSTLY see near 15-20% loss thru the auto drive train from engine hp to wheels hp. That would put the L98 at 192whp. MOST I've seen are near 210-220whp. Mild exhaust mods gets up 10-20whp if that. So 220-230 is about all you'll see...but it will vary on condition and dyno.

Thats roughly 275 on motor. Full intake bolt ons that dyno in the 250-260whp range is closer to 300-315 at the motor IMO.

Most "275" hp rated LT1 autos dyno 250's whp, but they really are rated same as the vette at 300hp.

 

I have a manual trans on mine so does that help a little?

 

Yep. few more % points Figure another 10hp or so, maybe 15. These are all just rough guesses. Autos loose 18-20% typically. Manuals lose 12-15% typically.

 

My 1990 IROC 5.7 G92 (ORIG. 198000 miles)when it was stock dynoed 255whp with a full exhaust system and air box cut out. This is with SLP 1 3/4 headers.

 

Wow, good numbers. Seems on the high side of the "norm" you see posted around but doable I suppose. And then again not all dynos will read near the same. 10-15whp variance is common across the country

 

I forgot to mention that with a chip tune. ItsMikey 89 GTA G92 5.7 dynoed 251whp on the same Dyno and he too has a full exhaust system with Dyno Dons 1 3/4 dual cats and Magnaflow catback. My cay has dual cats too. I think dual cats helps also.

 

Definately some power to be had in a chip tune. Abit of advance curve tuning and fuel tuning helps on everything. These cars do run a tad rich. Mine was dyno'd originally with some bolt ons at 246 with stealth ram intake and was 12.4 to 1 12.5 to 1 air fuels. Later added rockers, changed injectors and underdrive pulley...254whp on a different day same dyno but running 14.2 to 1 Figured 10 hp more was left in it.

Getting 250's with stock TPI is doing very well IMO