"On any OHC engine, it would be a good idea to always check the top
of the head for warpage. You're correct that the top sealing area of the
gasket and top of the head are milled. Should be obvious that the towers, and
rocker adjusters, are all removed to allow the top of the head to be milled
flat. Look at a feeler gauge, check the thickness of a 0.020" blade. A gasket
could still seal with 0.020" warpage to it. Now look at the camshaft..while it
MIGHT be able to withstand a 0.020" "bend" in it, it will not last for long.
I've seen snapped camshafts due to a warp in the top
of the head. Once both top and bottom are surfaced (milled flat), you should
install some cam tower shims. I picked up a set from Stan Chernoff.
Cheers, Tom"
Tom, Philip and others...
I had an L-16 in a 620 pickup that snapped THREE camshafts...I finally bought a
junked head and never snapped another one. I know the head was milled (on the
bottom) but nobody ever mentioned the top or the cam towers. And yes, the cam
rotated perfectly freely when I installed the new ones, and the engine would be
just fine for thousands of miles, but eventually they'd break.
The moral of the story...if it's me, any time I remove the bottom of the cam
tower, I'm going to have them bore-aligned. I would suspect that a cam for my
U20 would be a lot harder to find than the L-16 cams were 20 years ago.
(And that means LOTS more expensive!) But shimming the bottom of the towers
makes a lot of sense. Thanks for the info.
Fred J.
69 SRL 09546
(Elk Mound, WI - 55F and not a cloud in the sky)
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