My Mac headers are not level. The middle two flanges are fine, but the two outside flanges are raised each about 1/4" from a straight edge. I searched for this but couldn't find anything. Will this be a problem or will the flanges be pulled in just fine by the header bolts during install? Thanks

 

Are they new? If they are, send them back.

If they are used, they maybe a little warped from the previous owner. The MAC's do not have a continious flange (one of the very few drawbacks of MAC's), so they can warp from car to car. If they are not coated, You could probably take them to a muffler shop and have them heat up that primary and bend it into position. I would not try to horse it on the car like it is, by torquing down the header bolt really tight. The LT1 heads are aluminum and may not like that.

Dan

 

I got them new from Jet-Hot. I'm not sure how their return policy works, I'll have to check into that. Now why wouldn't they create a one-piece flange? Doesn't make much sense to me, their design is just asking for problems. Anyone else have issues like this?

 

Had the exact same issue. Every time I would have to take the MACs off they would be warped a little bit more.

 

Were you able to put them back on after the warping without leaks or stressing the threads on the heads? I suppose if I can press down on the primary and bend the tube back into place on a flat surface, I should be ok, but I don't want any problems.

 

Are you able to push them flat? If so, then I doubt they would be able to damage your heads. Make sure you don't use short header bolts.

Dan

 

Mine were like that when I got them brand new from MAC. My car was in pieces and it was my only mode of transport at the time so I had little choice but to make them work. I bent them as best I could but they still leak some even with copper gaskets. I was not at all impressed with the quality of MAC for how they are so often raved about, I wouldn't buy them again and MAC was not willing to help with my problem at all, granted they were already installed at that point. They need to invest in a bit more R&D and some customer service if you ask me.

 

Mine arrived in perfect shape from Jet-hot, as far as the flanges are concerned. The copper gaskets are not the best choice if you need to seal a flange that's not perfect. I had a few tiny leaks with my copper gaskets with my MAC's. Mr. Gasket Ultraseal gaskets work great. They are a composite construction and mold very well to the flange to seal nice and tight. Felpro header gaskets are pretty much the same, and seal great too.

Dan

 

When I first got them they were way off so I had to get them bent back to normal. They worked alright for a couple of years but this last time I took them off they were not aligned right again. I also dont think I ever got them to seal perfectly. I will not be buying MAC again or any header that doesnt have a solid flange.

 

Yeah I hope I didn't make a mistake...

I bought the stock GM gaskets after reading good things about them. I guess I'll see how well it all seals in a few weeks. If you guys read this, did you use Breslin bolts? I've heard only good things, but is it worth the extra cash? I worry that my warped condition may lead to an increased chance of bolts backing out, so I wouldn't mind spending a little more if the Breslins work. Thanks all.

 

Regular header bolts work great, at least they have for me. Just snug them up every week for a couple of weeks and they stay tight permanently after that.

Dan