Ok im swapping my 88 over from throttle body but i have a tune port set up off of a 86 iroc. Why is the intake different and can i just use a 88 iroc tune port intake. As far as i can tell the only thing different is the center bolt holes. Any help would be great. Thanks a lot.

 

TBI Heads have to be modified for TPI the center bolts that bolt the intake to the heads are different.. you will need the TPI heads or you will have to redrill the holes at the same angle as the other bolt holes...

 

You will need new heads, the TPI set-up, and the wiring for the TPI.My car was originally a 305 TBI, but now is a 355 TPI.The TBI heads are junk, and don't flow for $hit.It would probably be easier to buy a wrecked TPI car, and use the motor/wiring for your car.mine is wired up with a painless kit, but I would just get a complete TPI wire harness.

 

gm made a change in the center two bolts on all motors in 87. They changed the angle of entry into the heads that is the difference you see. Find an intake for the later engine and the problem is solved.

 

In 87 GM changed the angle of the 2 center bolt on each side of the intake manifold. To use a 86 intake with a 88 head you have three choices to get it to work.

1. Elongate or re-angle the bolt hole on the intake manifold. The bolt needs to run at something like 72 degrees from the head surface.

2. Buy a intake base for a 87+ heads.

3. Replace the heads with 86 or older style head. The stock TBI heads do flow badly, but unless your replacing the cam as well the heads won't gain you much because the only thing worse than the heads, is the cam.
I'm running World SR Torquer 305 head, they are available in ether bolt alignment and work will with a LT1 cam.