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Old 01-07-2013, 08:11 AM
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If you use those pistons (flat top) make sure you have 1971-1979 cylinder heads with no less than 90 CC combustion chamber volume or you will forced to use a large percentage of 108 octane racing fuel. The alternative would be to machine a dish in the L2359NF pistons. The L2359NF or L2359F pistons are Sealed Power VMS 75 alloy which is a thicker medium eutectic silicon alloy forging. The top of those pistons will take a dish .300"deep x 3.00" diameter.

With no less than 90 CC combustion chambers, and Fel Pro 8518PT head gaskets that have .039" crushed thickness, your 455 engine will have 10.6:1 static compression ratio. That is borderline for 93 octane pump gas with the initial timing advance set where the engine will run best. There may be off the shelf dished pistons available for the 455 engine but they are smog pistons made of 4032 hypereutectic 18% silicon alloy. My 455 engines had 1963 heads with 70 CC combustion chambers and had 11.8:1 compression ratio. I had to use 100% 108 octane VP C-12 racing fuel with the initial timing set anywhere.

Standard 455 Pontiac rings are 5/64" top / 1/16" second / 3/16" oil. The 455 engine has high thrust loading so GM used a 1/16" second ring in an attempt to reduce cylinder wall wear. The 455 SD racing engines used 1/16" top and second rings and the pistons were forged 2618 (2% silicon) eutectic alloy. The forged pistons and 455 SD/RA-IV camshaft is the reason why the team of engineers who developed the optional 455 SD engines were fired in 1975. . The 455 SD engine could not comply with emissions tests mandated by the revised 1970 EPA Clean Air Act, even after it was tested and equipped with the relatively mild 1966 HO / Tri-power and 1969-70 Ram Air III camshaft. The 1/16" rings and the low silicon pistons had too much blow-by before they reached operating temperature. .
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