In researching online, it looks like the early Gen 1 Coyotes used a fine pitch thread M10x1.25mm stud. Later Gen 1 engines and Gen 2 Coyotes appear to have been changed to a course thread M10x1.5MM stud. Researching on Summit Racing, I purchased the Stage 8 locking fastener kit 8914C for later Coyotes. However, I have seen posts indicating Gen 3 Coyotes have the fine pitch M10x1.25mm studs. I am confused and I guess I will just wait on the header bolts I bought and compare to the thread pitch on one of the studs from my engine.
Is there a mixture of course and fine thread manifold studs out there in production. According to Summit, the fine pitch was only used on early Gen 1 Coyotes, but the comments by some that the Gen 3 uses the fine pitch seems to contradict the fitment info from Stage 8 shown on the Summit website.