In order to get to the two oil galleries that feed the center mains I drilled 3/8" holes in the main gallery. I was able to reach through with a 5/16" spherical end rotary file on a die grinder and radius the entry and create a bit of a pocket. Then the hole was enlarged to 25/64" and tapped 7/16"NF. A set screw or short bolt will plug the hole but won't be inserted far enough to impede oil flow. Some good quality thread sealant should prevent leaking.

Bob,

I'm planning on doing the same thing for my high RPM 170 build. See it's right here on my note pad!

Can you tell me how thick the outer wall of that passage is? I'm thinking I can either use pipe plugs or spot face the surface and use a copper washer on a bolt. I may also feed the oil galley from the ends as well as the middle to ensure adequate and equal pressure to all the main bearings. 8000 RPM here I come!

_________________
Joshua

interesting,,
more on this subject?