Exhaust Manifold Bolts

I know what size bolt and length I need. But does it matter what Grade or is there a special type bolt for installing exhaust manifolds?

 

I used the grade 5 I believe from Lowes/Home Depot and 3 of the heads of the bolts broke off. I replaced all with grades 8's and lots of anti-seize and they seem to be holding up. Not sure why the others broke.

John

 

I was thinking about going with Stainless to keep from rusting and getting brittle. Just not sure how the heat will affect them.

 

There are kits that use a steel stud and a brass nut that is supposed to reduce the chance for seizing. I'm going to something like this soon.
http://www.americanclassic.com/Google_Base_HTML_Pages/EXH-B1-1963.htm
http://www.amazon.com/1959-1980-Corvette-Exhaust-Manifold-Stud/dp/B000GF31NC
There are many different lengths and applications available.

 

I'd avoid stainless. I don't believe there is any advantage in terms of seizing less, and they are no stronger than plain steel bolts.

If It were mine, I'd use high quality grade 5 or grade 8 black oxide steel bolts and liberal anti-seize paste. The studs and brass nuts would be another option, although I suspect that the stud kits linked above are not for the manifold-to-head mounting, but instead for manifold-to-pipe. I used a couple of studs on my J-10 258 manifolds, but those were mostly for ease of assembly. The studs came out of the hardware drawers at my local NAPA.

 

Purchased Grade 5s and Anti-Seeze at lunch. Hardware store did not have grade 8s in length I needed. I did some research and most places said avoid stainless with heat. Maybe I will never have to remove them again anyway.
Is there a sealent that needs to be applied to gaskets?

 

You using gaskets on the exhaust manifolds? V8, 6?

Warning - exhaust gaskets under exhaust manifolds won't last very long. They'll last a while, but it's better to use no gasket like the factory did.

The Wagoneer guys like the Remflex gaskets http://catalog.remflex.com/ or copper gaskets under headers. But iron exhaust manifolds should not need a gasket if the sealing surfaces are in good condition.

IMO any sealant you put on exhaust gaskets will soon burn away - not much point.

 

Huh I was thought they came with them, all the what I thought original engines had a gasket on them. I also noticed on some of the manifold bolts I've taken out they were hollow in the threaded section, is this to help with heating and cooling possibly? I can get a pic if necessary.

 

Yes, the hollow bolts are factory. Not sure what the purpose is - maybe if you get them hot they come out easier because they expand less?

No gaskets under iron exhaust manifolds. At least back through the '70s, exhaust manifolds came from the factory with no gaskets - iron on iron. Even the pipe-sealing doughnuts went to steel in the early '70s, and later manifolds have no provision for a gasket at all; the flared pipe goes right up against the iron manifold.