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On Tuesday, August 6, 2013 12:10:47 AM UTC-4, Terry Coombs wrote:
Anybody here have any experience with hoppin' up the engines ? I've been

asked to mill .045" of one from and OHV motor , don't know the brand . One

thing O found after I clamped it to the mill table , the area over by the

pushrod area is about .005 down from the area around the piston .
Snag


How flat was it before clamping the head down? I have no experience on
small aircooled engines, but have worked on a couple of car engine heads
that were blowing gaskets. Did these with a big file and a carpenters
square to check for flatness. As I remember the heads were out of being
flat by about 0.030. I probably got them flat to within .005 and they did
not blow any more gaskets.

Dan

The head is pretty flat , max difference is right at .005 , and there's a
pretty good impression around several of the bolt holes - I don't think this
head distorted at all when I clamped it , it's like 4" thick . I was mostly
checking to see if the valve vcover sealing surface is parallel with the
bottom surface last night . It was pretty dern close - checked with just
enough force to keep it from sliding and the same measurements after firmly
clamped . I was wondering if the slight difference was designed in to
cantilever the clamping force over towards the piston area .
--
Snag