Guys/Gals..
I purchased a 87 IROC TPI Auto LB-9 about a year ago.. The engine was in great shape and it only has 90,000 orig miles.

My question: I have a plan of making improvements to the car but since purchasing it I have performed the following:

1.) Air Foil
2.) 3:42 Posi
3.) Rebuild 700R-4 with shift kit
4.) 2800 Stall Converter
5.) Edlebrock ported Intake (with stock runners/plenum)
5.) All air conditioning and compressor/hoses removed
6.) Free flowing exhaust with Magnaflow muffler/ Hi-Flow Cat (single)

***The IROC feels quick/responsive..even with the "peanut cam"... but realistically what type of performance increases would I see with just these mods..??? Stock LB-9 Autos ran 15:5- 16 sec 1/4 miles new... I haven't taken it to a track to get official numbers. It feels faster than 15. I own a 89 TTA so I know what high 12s feel like -

In the future I will go 1:6 ratio drivetrain, LT-1 cam, and maybe some better heads... the IROC is a daily driver.

 

Subscribed and Welcome to the Board.... AS far as your performance, you won't know until you hit the track for some tangible evidence. Many have sourced a set of the '88-'91 Corvette heads (113 casting) for some better flow.

 

The LT1 cam is only a little big bigger than the stock L98 style cam and shouldn't give the computer any fits. Your car is probably in the high 14 second time range so far as the quarter mile is concerned. The peanut cam is what holds back the mods that you make so changing it is a good idea.

A high stall converter really wakes up an automatic trans car. The stall and gears should have really woke your car up in the performance department. With the lock up converter its the best of both worlds. Good performance on acceleration since the stall keeps the motor in the torque band & fuel economy with it locked up in overdrive. The 2.73 gears a lot of thirdgens had really zap the performance factor. 3.23-3.42 gears are a good street performance gear for TPI motors.

Do you have to do emissions testing? Look in to the Edlebrock center-bolt style aluminum heads. They flow better than stock and are a good match for a mild cam. Those heads also have the internal gas cross over passage like the stock heads so they are emissions compliant.

The L98 corvette heads (113 casting) are used on the ZZ4 crate engines. They are a good choice too. I think you'll get more of a gain from an aftermarket company like Trick Flow or Edlebrock though. The corvette heads also don't have the gas cross over passage so if you have to deal with emissions they won't work. Unless where you live lets you have an external cross over package like the C4 corvettes have.

 

Thanks for the advice and opinions guys.

Yes I have been reading up on this board regarding the Head combos...I am thinking of going Trick Flow with LT-1 from a 93-94 year to complete engine work. I was thinking of going World Products 305 heads but for some extra franklins I might as well go with the better product and avoid having to do this again...

Unfortunately I live is So Cal ...so emissions will be an issue. I will be keeping the air pump and the egr. I was thinking of doing a exhaust straight pipe and have a bolt on Cat for emissions...but the extra 2 hp may not be worth the hassle so I will probably stay with the hi-flow cat.

Question: If I add the trick flows, 1:6 ratio drive train and a adj fuel pump reg....what type of 1/4 times am I looking at??? Low 14s...? I will be keeping the CR in the 9: range for 91 Octane.

*** My wife owns a 95 TA, it's totally tuned up with new OPTI and a 2300 stall and hate to admit it but the "Peanut" cammed IROC with the Stall and the gears is a TON more fun to drive on a daily basis--thanks in part to her lame 2:73 Axle.. What were they thinking putting that on a LT-1!!! LOL...

 

With those mods probably in the mid to low 14 second range in the quarter mile. Ha yeah the 2.73 gears are in there for fuel economy and keeping noise levels down on the highway with low rpm's. A good high flow cat is whats needed. The gains with a straight pipe are very small on a street car.

I'm in northern California so I have to deal with the emissions stuff too. It's a real pain but, it is what it is.

 

Agreed.. the 2hp difference isn't worth the hassle or the risk in So Cal emission's police I will be sticking with a Hi-Flow Cat.