?? on Drilling 3/32 Hole in Rocker arm

Billr57

Well-known member
When you drill out the 3/32" holes on the valve side to 1/8" do you want to champer them also or just drill them to 1/8"?

Thanks Bill
 
Howdy Back Bill:

Just drilling them out to the 1/8" size is adequate. Champering is not necessary. What is necessary is a good clean up of the area after drilling. Remove any shavings and smooth any nicks or roughness that can promote crud from catching and building up in the holes.

We discovered this subtle difference between early and late rocker arms by making running the drill bit through the holes as a standard part of cleaning out the whole rocker assembly. And, as usual, we found this out the hard way- broken rocker shaft, destroyed pushrods and rockers, and lots of noise.

If the system is absolutely clean and is well maintained, the extra 32nd of an inch is probably unnecessary. The problem is that, when a system is not well maintained these tiny holes are the first to plug up, causing unnecessay wear and problems. In these cases, a little more hole area may make all the difference. And in 40 year old OEM adjustible rocker arms a little more engine blood (oil) can't hurt.

Adios, David
 
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