Patrick,
OEM thickness of the cylinder head is about 4.258". Measure
the thickness after milling and install shims to compensate
the for the difference after milling.
As to measuring the chain slack before and after: two problems.
First: The components really should be replaced at rebuild, and
you would be measuring the slack of a worn out chain.
Second: The U20 uses four gear, and two chains. You can not
measure between the crankshaft and camshaft gears.
Cheers,
Tom
>From: "PATRICK P. CASTRONOVO" <slick@mohaveaz.com>
>
>How would you know how much thickness of the cam tower shims you should be
>using after a mill job. You could tighten up the camshaft chain also in
>the process of compensating for the mill, if you knew how much play you have
>in the chain, vs how much you "should" have in the chain. I think before I
>removed the head from the car, I would see how much play I had in the chain.
>I would lay a straightedge from the crankshaft gear to the cam gear, then
>depress the chain taking all the slack out of the chain, and measuring the
>distance from the straightedge to the chain. Armed with that information, I
>then would talk to a machinist that was familiar with how much you would
>need to shim to come back into a tight tolerance with the chain. Then add
>the metal that was removed from the head to that amount, to come up with the
>right shims for the cam towers. And be sure not to mix up the cam towers,
>nimber them and put them back in the same place.
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