Replacing exhaust manifold bolts - grade 5 or grade 8

[thegreatjustino]

Today I pulled all 11 bolts out of the 170's exhaust manifold to replace the leaking gasket. Two snapped off, one was an incorrect size, and all of the others are in some way pitted or otherwise degraded.

I'm going to pick up all new bolts and lock washers tomorrow along with some anti-seize. Is it generally recommended to spring for grade 8 hardware for exhaust manifolds?

 

[Bferrari]

Nope, use grade 5, they work well.

 

[B RON CO]

Hi, the manifold on my 170 was warped. The machine shop put it on a giant belt sander to flatten it out. I'm going with a new manifold and 2" exhaust in a couple months. You should check out Fordsix.com and get the Falcon Performance Handbool to get the most from your Ford 6

 

[blubuckaroo]

Grade 8 would work. But if you ever do break one off, it's really hard to drill out a grade 8 bolt.
I think its more important to use good quality fasteners. There's a lot of junk out there and not all grade 5 or grade 8 are actually as they are marked.
I think I'd just go to a good bolt store and get good quality grade 5 black oxide bolts.