I know use Felpro. I did that and went with the 1406 gaskets from Advance. I remember that during the MAC header install on my 94 Trans Am that the gaskets didn't fit right. They were too short and I cut the tab off the end (the convenient hanging flange). I finally got a good seal on my lower exhaust system and can hear a huge leak up top. I inspected the headers and found a leak (carbon buildup) at the rear passenger side header. Is this set of gaskets mislabeled? I paid $20 for these, what are the Felpros that people are saying cost $12? Do I need the stock GM gaskets back. Are the Felpros side specific? I never thought to check that.

Thanks,
Chris

 

From what I've heard Fel-Pro gaskets don't work well with MAC headers for the exact reason you noticed, the outside slots don't line up with the bolts. That's probably why they're leaking. I heard the stock GM metal gaskets work the best with MAC headers.

 

Evilbox, thanks for the reply. I am always reading on here about how good the Felpros are and most of the time they are talking about the MAC headers (I thought). I saw one other post about the same problem I have, but not the answer.

Thanks,
Chris

 

TTT, I am not really understanding something here. If all LT1 heads are the same, then why don't the 1406 gaskets fit the bolt holes when you install MACs? Are the gaskets side specific?

 

For the outside header bolts, there are 2 different sets of threads in the heads. One set is farther out (which MAC headers use as well as the stock manifolds), and the other is closer (which most aftermarket headers use). Fel-Pro gaskets happen to use the inside threads. Hope this helps.

 

On my MAC headers I used NAPA metal gaskets. At first I used NAPA metal mesh gaskets but I quickly blew those out and had to replace them. I did mod the metal gaskets by cutting a tab in the last holes so that I could slide them down onto the header bolts without removing headers.

 

Evilbox, AH HA said the blind man-I never looked at the heads that way or even noticed it when I put them on. Nevermind that explains all. I was looking at my friends supercharged Formula with MACs last night and saw his didn't reach the end either. He must just be lucky with his.
Rocmemphis-I may try them or buy the stock GMs if they fit.

Thanks,
Chris

 

i bought some copper ones off of ebay

the 1406 felpros didnt work for me, nor did the stock gms


i bought 2 different sets before finding the right one

 

I took your advice and looked on Ebay, but could not find any. If you run across them again let me know.

Thanks,
Chris

 

felpros suck..get GM metal gasket...they are THE BEST, and only 12 bucks a pop at your local GM dealer

 

That is what I was going to do, but supposedly they don't fit the MAC bolt holes either. If they do correct me here, please tell me some good news.

 

1406s worked just fine with my SLPs. I put some high temp RTV around the ports for some extra insurance

John