Skidmarks

I have a '88 Corvette L98. I also have access to a complete TPI setup off a '90 IROC L98.

My plan is to take the IROC TPI and port the plenum and base and either polish the whole setup or have it powder coated. Then I can make the swap on a weekend.

I know the '90 unit doesn't have the cold start injector, but I don't believe that will be a problem. I believe the fuel rails are different, but I dont see that being a problem cause I can use my original rails.

My concern is if there is any difference in the base between my '88 unit and the '90 IROC unit. Is there anything that will make the swap difficult if not impossible.

Thanks for the help.

cheese_kake

To my knowledge the corvette and camaro tpi units were exactly the same with concern to L98's. But as far as going from 88' - 90' I dont remember, because there are differences from 85-92. IE as you mentioned cold start injector. And as you know the dizzy cover on the vette's are aluminum. If I remember right the changes in the TPI setup were from 85-87 style , 88-90, and 91-92. So if Im remember correct you shouldnt have a problem at all.

ZZ28ZZ

The EGR system is different between the vettes and 3rd gens. Can't remember if the stock intake from a 3rd gen has a provision for the vette egr tube. I know my Accel intake can go either way.

cheese_kake

Your right about them being different but my buddy awhile back used a camaro base on his vette' for a few days untile he got his other one back, he sent it to get polished. I dont remember him having any problems hooking up the EGR. Its possible that they're just different but compatible.

Rob Wade

Your camaro base won't have the egr provision in it. Only the vette base has that opening.

Skidmarks

Ok, thanks for the answers.

If I understand correctly, the base should bolt up with no problems, I'll just need to do a delete with the cold start injector and the EGR.

Thanks again.

cheese_kake

Wade, are you kidding me. 3rd gens had the egr opening.

MattODoom

iTrader: (1)

3rd gens have EGR passages in the intake itself that enter through ports in the heads. Corvettes have a tube that bolts on the intake and feeds off the exhaust manifold as the corvette heads do not have egr passages in them.

Skidmarks

I know that's absolutely correct in regards to the vette L98.

Rob Wade

Let me rephrase that. You can't use the iroc base plate on your corvette because you don't have the egr TUBE provision. You CAN use the corvette intake on your iroc. Did I 'splain that better now?

Skidmarks

If I just delete the EGR entirely can I then use the IROC base on my Vette?

Rob Wade

Yes

85C4fanatic

The 85 vettes have the EGR passage in the intake. Only Vettes with aluminum heads have the external EGR passage.

Skidmarks

OK, thanks for the help. I guess I'll get to porting and polishing.

Mark 89Formula

The angle at which the center intake bolts enter the cylinder heads is different between the L98 AL (90 degs) and iron (72 degs) heads. Not a show stopper, just something to be aware of. You can grind the holes in the IROC base to allow mounting on the AL heads. Aftermarket bases (gen 1 SB, not Vortec) are set up for both angles to allow it to bolt on without modification.

Skidmarks

Ok, to sum up and see if I have this clear.

1. I can delete the cold start on my '88
2. I can delete the EGR

(No. 1 & possibly 2 will require chip reprogramming)

3. I can use my '88 throttle body even with out the cold start provision

4. Plug the MAP sensor vacuum source since I don't need it with my MAF system.

5. If I elongate/enlarge the center mounting holes on the manifold, it should work with my aluminum heads.

Am I missing anything?

Shagwell

your list looks good. - that's all I know of. You may be able to run your cold start/fuel rails if you re-use your runners. not 100% on that though...

MattODoom

iTrader: (1)

I have an 88 with no CSI. Im using an all 88 TPI with 89+ SLP runners. All I did was cut the metal line to the CSI and weld it closed at the cap (!!with it off the car!!). Then I run an 89 bin in the ECM that adds fuel to all inj at startup

-Matt