Can someone give me a ball park idea as to how much I need to elongate my pushrod slot when swapping to 1.6 rockers, on a 416 head casting, if it matters. .050"? 1/16"

My machinist reminded me that I needed to do that, and thought I didn't have much chance doing a good enough job with a file and a drill, but I do have a mill, and a 5/16" end mill so....

Thanks

 

Maybe its just because of the severe hangover but going from 1.5 to 1.6 rockers shouldnt make any difference...

 

Going to 1.6:1 rockers might possibly "correct" what you may have lost by going to a higher lift (smaller base circle) cam. Then again, depending on the castings and their stock slot machining, installed valve stem lengths, spring installed height, specific rockers you are using, and the resultant rocker geometry, you may or may not have to open the slots. How much is a question I can't answer. I've taken .050-060" for moderate lift cams and '416 heads and had plenty, but that doesn't mean that is a good number for your application. Mocking up a head on the deck, installing a pair of lifters and pushrods, and measuring would be the most certain method.