Editing Pontiac V8 engine (section)
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==Pistons== Generally, using flat top pistons are the best way to go. There may be cases where a dished piston is needed, but the cost is generally higher than cast flat tops. In 1967 the 400 4bbl engines went to new valve angle and placement and all Pontiac V-8's 1968 and newer. Newer valves don't line up correctly with the 67 2bbl, any 326 or all 1966-back piston valve reliefs (and obviously vice-versa), the correct piston has to be used if any sort of aftermarket high lift cam is used, or else there may be destructive valve to piston interference. There are 8-valve relief pistons available to fit all the valve angle differences used through the years on Pontiac 400 engines. While these pistons will get the job done, from a high performance standpoint they are not desirable partially due to the lower compression. Pontiac went to an advertised 7.6:1 compression in about 1975, due in part to the design of the top of the pistons. Pontiac pistons from the low compression years have a 45 degree machined outer edge of the piston top. {| |[[File:Oem pont pist.jpg|thumb|450|center|Note 45 degree cut (arrow) to the top edge of the low compression piston]] |[[File:8 vr pont.jpg|thumb|450|center|8 valve relief rebuilder-type piston, undesirable for high performance use]] |} ;[[Pontiac V8 engine #Parts interchangeability|Return to Parts interchangeability]]
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