Bob, I suspect .175 is OK. An easy way to gain a small amount of compression. I did mine .020 and the block the same. Bored .125. Then sprung for aftermarket pistons for a compression increase to 9.5. A note of caution! The cylinders should be sonic tested to make certain the walls have enough meat for this much bore. I did not and payed the price. One cracked. Necessitated a complete teardown and sleeving the affected cyl.
In this case we are just using a common replacement piston at 0.030" oversize, so cylinder walls won't be a problem.
I am just setting up for piston valve clearances and have them to be about exh. at .275" and intake at .270" without a gasket.
With the Ford valves, and smoothed combustion chambers, the volume is about 97.5cc which, with a .015 head gasket yields about 7.02:1 cr, and with .045 gasket gives a 6.74 cr.
Removing about .050" yields about 7.25:1 compression ratio. .100" gives about 8.15:1 and .150" gives about 8.89:1.
After removing material, the measured combustion chamber was about 75.4ccs giving about 8.94cr.
After surfacing, without a gasket valve piston clearance is about 0.120".
Last edited by Bob; 03-14-2019 at 02:00 PM.
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