piston to wall clearance
I have had several 389-400-428 engine combos built for me using TRW pistons including 3 400s using the L2262s style you are contemplating using, over the last 40 years. I have always used a clearance setting of 5 to 5 1/2 thousants on all my forged piston motors. The engines always sealed and Never locked up due to too tight clearance. Use 2 to 2 1/2 thousants on cast pistons and 5 to 5 1/2 thousants on forgings. Use a Double Moly ring set or double plasma moly with your pistons -thats what Pontiac fitted in all its high perf engines-the low performance combinations (usually 2 bbl 400s) used a single moly ring on the top rail with a cast iron derivitive ring on the bottom ring rail. That low po combo would seal almost immediately but would not have the long term durability of the double moly combo.
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