I've got an 89 IROC with a TPI 350.

After a recent head gasket replacement I decided to get a new base, runners and injectors. I got an Edelbrock base and runners off of EBay and I bought 24# SVO injectors from Summit. After I completed the installation and started the car last night it sounded like I had the biggest vacuum leak in the world. Luckily I got the engine to idle up high so that I could feel around, listen, and spray suspect joints. I had no luck finding this major vacuum leak. It sounds like a very sizeable hole, but I just didn't see anything, even after disassembly.

I think that my problem may be related to the way that I blocked the Cold Start Injector. Below are some pictures of my base and runners on the drivers side. Do I need to block any of the other holes shown? You can see the plug that I made on the runners. The injector O-rings all looked good. Is there anything else I should try?

Thanks,
Joe

 

I guess I'm going to attack it again tonight. I think I'll try pluggin' hole "C". I'm also going to try putting some RTV on all my gaskets.

 

Let me guess. You didn't have the air cleaner bellows on the TB when you started it up. That loud 'vacuum leak' you heard was the IAC.

If you're not that green (i've seriously seen it more than once), i apologize.

With a MAF car if you left the CSI hole uncovered the engine probably wouldn't run at all, and would certainly set a low MAF code in no time. But, assuming you did buy runners for a CSI car, all you need to plug is the hole where the CSI comes into the runner. No need to mess with the base or anything else.

 

I think ed is right I had the same problem when I used the edelbrock runners.on the tube you have it marked as C will leak at the top of that same tube where it meats the plenum

 

Thanks for the replies.

No, I didn't leave the bellows off or leave the IAC out, but I could see how someone could do that too. Sorry I'm not one of those.

I got it running just fine last night. I plugged hole "C", but that shouldn't have affected anything. (For refrence, hole "A" is the passage way that leads to the PCV valve. Hole "B" is part of the EGR system)

The bottom bolts on the Edelbrock runners require longer than stock bolts. Unfortunately since I dind't buy these new I didn't have the correct bolt. A trip to the hardware store fixed that. I think the replacement bolt may have been too long and bottoming out before it sealed the runners. So I cut the bolt shorter.

A whole bunch of RTV and a few cuss words getting it all lined up again and somehow it's running again. I really don't know what fixed it, but everything seems good now.

Does anyone know if I can get helicoils for metric threads?

 

Sure can, most auto parts stores should carry them.

 

You shouldn't block the PCV or EGR holes. Just block the single hole the CSI sits in. Period.

Anything else will stop air flow from where it normally goes.

PCV GOOD! EGR GOOD FOR EMISSIONS!

The biggest vac leak that occurs from alot of people, myself included, is to forget to plug the Brake booster back into the back of the plenum.

 

I just had the same problem, using early large tube runners on my 89 GTA. Yes hole "C" definitely needs to be plugged. Theres no matching hole for it in the late plenum, and it sucks air from under the plenum. Obviously the hole for the CSI also needs to be plugged as well.

 

Brake booster hooked up?

 

Isnt hole C for the EGR? Doesnt it lead upto the plenum? Yea check the brake booster, I forgot that once

 

What I'm saying is that if you use early runners with a late plenum, hole C causes the vacuum leak and must be plugged.

Theres nothing for hole C to mate with on a late plenum, it just sits out in the open underneath the plenum and sucks air!