Log Manifold bolts
 

I ordered a 12 bolt exhaust manifold set and got only 8 bolts! Will hardware store bolts hold up with the heat or should I wait for Ames to send more? I need my car back on the road I'm missing work! Thanks

I’ve used Grade 8 hardware store bolts and they work fine.

Only problem I have found using hardware store bolts is you can't always get the correct length.

I purchased a pair of new reproduction Ram Air manifolds many years ago. Almost none of the supplied hardware was the correct length.

To really get the full and proper thread engagement I had to cut the bolts I ended up buying down. Even buying bolts in 1/4” increments wasn’t going to be good enough, I cut them down in 1/8” increments to get what was needed to do it right.

If I had a nickel for every Pontiac exhaust manifold I've used, or seen grade 2, 5, bolts used in, I'd probably have $10. The only time it's going to be a disadvantage is when you're trying to remove them, and if you coat the threads with never seize, you'll eliminate that problem.

Grade 5 is what I believe the factory bolts were, but since they're not a critical fastener, any 3/8" bolt works. If you're worried about them not rusting into the cast iron heads, stainless will nullify that problem , but you'll likely end up making them to custom lengths as has already been touched upon.

Any correct length bolt with never seize, and send it. They can be changed out at a later date if you feel the need to.