Thread: 390 with 1U crank--> 410 , eh...pistons??

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A 390 has a 10.17" deck height. A 410 has a 3.98" stroke. Both have 6.489" rods. Take the 10.17 inch deck height, subtract the rod length and one half the stroke. The remaining number will be the necessary compression height to achieve 0 deck. It is 1.691" Most pistons are going to be set no more than .025" down in the bore, so we subtract .025" from 1.691" to get 1.666" The piston you want will have a compression height between 1.666" and 1.691" I believe most pistons you are going to find will be around 1.675"