Midnight_Z

Anyone have experience with installing MAC Mid headers 94/95 style?


I can get the OEM manifold gaskets from my Chevy Dealer for $30 a pair. I have been hearing that these have worked good with Mac headers. Percy's dead soft aluminum or Earls aluminum are my other options I have been thinking about. Felpro 1406's don't work with these headers because of the bolt pattern I guess.


I was thinking OEM gaskets and a nice thin coating of high temp silicon on each side of the gasket to prevent any leaks?

raroz28

I ran 94-95 Mac mids on my 97 for years with fel pro gaskets without a leak. Never used any sealer, just the gasket by itself and ARP header bolts.

Injuneer

You are aware that the LT1 heads have dual bolt patterns for the end bolts? Stock manifolds use the outer bolts, most headers I have ever seen use the inner bolts, matching the 1406's. Might want to check the MACs in this respect.

KYWes

I've got these headers on my '95Z and like them very much.

Originally I used Percy's header gasket and header bolts. The gaskets worked very well and lasted seven years. I didn't use any sealant.

I had a header bolt break allowing an exhaust leak which took out one side but that will happen with any gasket. The other side was still in good shape.

I'm redoing my headers right now and going to try Remflex gaskets and a new (for me) Percy header bolt called vibe lock.

GCEZ28

Which Percy's did you use? How are they holding up? And aren't the Vibe lock bolts like stupid expensive?

KYWes

Sorry for the delay. I wanted to check my receipts.

The Percy gaskets I used the first time were the metal ones (Percy's High Performance 66031 - Percy's Seal-4-Good Header Gaskets $39.95 Summit Racing). They worked very well. The only reason they developed a problem is because a header bolt broke causing an exhaust leak that burned the gasket. That will happen with any gasket on an exhaust leak. The first time I used a Percy header bolt (Percy's Split Lock Friction Lock Header Bolts 21003 $69.95 Summit Racing - discontinued) that had the set screw inside. These were split four ways on the end. You then screw in the set screw to spread the ends causing a tight fit. These did not work well for me. I had bolts come loose and one of the set screws broke causing me a LOT of trouble to remove, and that's an understatement.

This time around I went with the Remflex gaskets ($30.68 Amazon) as I had read so much good about them. They have been on for about six months now and I've experienced no problems.

Yes, the Percy Vibe Locks (310000) are very expensive ($64.49 Amazon). They work with just a quarter turn of the set screw to lock the bolt in. In six months I've not had a leak develop nor has a bolt come loose.

Injuneer

The key to a successful header gasket install is checking the header flange for flatness. If it isn't totally flat, you are going to have a leak. Get a steel straight edge long enough to span the entire length of the header flange. Put the edge of the straight edge on the flange and check for gaps.

I bought my AS&M's used from a buddy. He had checked for flatness and had them planed flat. They were installed on my car in 2000, using Mr. Gasket copper Ulta-Seal gaskets and ARP stainless bolts. 16 Years later and never a leak or a loose bolt.