i think, well pretty sure that i cross threaded the bolt for my header while putting them back on, i tightend all the bolts in then tried to put the last one in with the other ones tight, and didnt work and cross threaded it in, it is in my new pp 5.3's, any one know the size so i can get a tap and re-do the hole so i dont have a leaking header!! thanks a million... dwayne

 

I'm pretty sure it's a 8mm x 1.25 mm
Take a bolt with you & match the thread pitch, I'm almost positive it's 1.25.

 

thanks man, any others that are sure also just incase...thanks for the help, i just dont want to really mess it up...