I get 9.78 to 1 with a 19.3 CC dome.
I add the ring land volume which this formula does not include, but it’s nice to be really accurate with the compression ratio and some big bore pistons on some motors that have the top ring pretty far down the piston can have over 2.3 CCs of ring land volume detracting from the compression ratio.
Here’s what the TRW catalog shows for the compression ratio for that piston, but it’s wrong.
First this assumes that the head gasket is round and it’s not, it’s oval so it’s bigger.
2nd the stock deck clearance is not .001”
Also note in that catalog page that TRW list .015” ring groove shim stock, so whatever rings you use with those pistons make sure the back clearance is not excessive.
That bump on the peak of the dome has to go as it’s killing intake flow.
I dont know what compression your trying for, but that bump would be a deal breaker for me and send me off for a different piston that could get me to 9.5 to 1 with a 111 Cc chamber.
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Last edited by steve25; 02-04-2024 at 05:05 PM.
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