I have a 1995 Blazer 4.3 that I am having the tranny rebuilt on. While removing the Y pipe the some of the studs broke from the flange on the exhaust manifold, does anyone know what size the threads in the manifold are? The look to be around 5/16-18 but I want to make sure before I buy a tap.

 

Looking at what's available from RockAuto.com, it is a M10x1.5 thread. The stud was OE PN 15677737 and is 70mm long. I would go with one of the kits available at most autoparts stores for your replacement. The stud/nut type kits seem to last longer than the kits that are just a bolt with the spring.

 

Thanks!!