so i have this 302 with 351 timing, im trying to put it into my truck and as i tryed to put my header bolts in so i didnot loose them i realized that the thread is different. dose this mean heads could be from 351? or just newer or something?

 

It depends on the size of the bolts. From 1977 onward, the 351W shared the same head casting as the 302, differing only in bolt hole diameters, 7/16 inch for 302 and1/2 inch for 351W.

 

i think they are same dia. but the bolts will thread in 1/4 inch by hand. intothe oldheads andi knowthey arefactory 302 then this other engine the same bolts will only go 1/2 turn in and i dont want to put a wrench on them and break something.