Header Bolt Question

[mnmrmstd]

I'm installing a set Ford shorty headers (M-9430-P50) on GT-40 heads (1989 GT). I've seen the header bolt size for this application listed as both 3/8-16 " x 3/4" and 3/8-16 " x 1". The key dimension here is the underhead length: 3/4" or 1" ? Thanks for the assistance.

 

[TheBocSez]

Get the 1". More threads into the head and better clamping force. Tighten down and drive around for a few days, then tighten em up again while the engine is warm and your done.

If using aluminum heads, use anti seize and the recommended torque specs.

 

[vristang]

1" would be good, as long as it doesn't bottom out inside the threaded hole.

I am not sure what the actual length would be on those?

Do you have any other bolts laying around to use as a guide for length.

Maybe you could poke a stick or something in the hole, then measure the length of stick that would fit in the hole?


jason

 

[TheBocSez]

I think the 1" would be ok, I believe the headers he's using have a 3/8 flange so you lose 3/8" just to the flange plus just a little more for gasket thickness. That would probably only leave a 1/2" or so to screw into the head. (sorry, not good with fractions)