Header bolts
 

Are they 8 X 1.25 PITCH X 35 MM Long ?Got a set of NHP header but no bolts and want to replace them , Would like to have the bolts before I take the old manifolds off increase one or more break . Thank you guys

Unless the car came from the rust belt or lived it's life near the gulf, you probably won't break bolts taking them out. Mine came out smoothly and in good shape and I reused them. If you think your's might not, crawl under there and spray them with PB Blaster or Kroil, do it a couple times starting a couple of days early.

That said, my header bolts were the same diameter and pitch as the rest of the middling sized bolts on the engine. 8mm x 125 pitch I suppose. You can probably source the correct ones at a local speed shop.

The next time that I have any need to remove my manifold bolts, I will be replacing them with short pieces of threaded studs and matching flanged nuts.

I am always nervous, for installations like this, of the steel bolts buggering the aluminum threaded holes due to wear, accidental cross-threading, etc.

Removing the nuts is a far "safer" approach, with much less potential for damage.

Thanks - DM

Use all stainless and a high temp (nickel) anti seize compound on both the nuts and studs. An alternative for ease of future repairs is to use SS studs and brass nuts.