Join Date: Sep 2000
Location: Washington, Michigan USA
Header bolts will ALWAYS loosen up on their own, as they are so short that they don't stretch in order to develop and hold clamping force. I have always used ARP NASCAR header bolts - they are pre-drilled for safety wire and available either in 6-point or 12-point, polished stainless or stainless with black oxide finish. I torque them up, run the car for a few hours, re-torque them, and then safety-wire the bolts. It takes time, but it's a lot less hassle than constantly replacing header gaskets. Have NEVER blown a header gasket.
Another solution is the locking bolts that use a little C-clip (can't remember the name), although clearance to the header tubes isn't always adequate to install/remove the clips (which is why I like safety wire - no clearance required).
I see cars at shows all summer long with header bolts missing - you don't have to live with this - just takes some time and spending a little more on quality fasteners.
Might as well rant now about "chrome" or "stainless steel" bolts - 99% of the ones you buy at speed shops or out of catalogs as "dress-up kits" (except ARP) are junk, and have Grade 2 or less strength - shouldn't be used on anything except valve covers. ARP fasteners are made from special stainless alloys, and are stronger than Grade 8 bolts (which is why they're so expensive compared to the chrome or stainless "dress-up" junk). I've dealt with engineered high-stress fasteners all my life, and it makes me cringe to see some of the applications I see on show cars. Don't ever use anything less than Grade 5 (3 lines on the head) on a car, and use Grade 8 (6 lines on the head) any time it's for steering, suspension, or brakes. Grade 5 and 8 also have rolled (not cut) threads; don't ever use a "hardware store" bolt with cut threads and no head markings (which is what most of the "chrome" bolts start out as) anywhere - your life may depend on it.
'69 Z28 Fathom Green