I think that should be 4.528-4.530". A head at 4.258" would have one heck of a
compression ratio!
Thomas Walter wrote:
> 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.
>
--
Gordon Glasgow
Renton, WA
http://www.gordon-glasgow.org
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