Quote:
Originally Posted by Brad_bb
Nice b-man, Are you planning to reuse the pistons or?
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Both the 421 and 389 pistons were damaged by hammering them out of rusty bores, so enough of the pistons were damaged that each set became essentially unusable. With that said, using old pistons really can't be done that often anyway. The amount of bore wear on most of these old injuns makes new pistons pretty much mandatory. I photographed two of the pistons that didn't have hammered-on tops to show the valve reliefs here.
In keeping with the theme of this thread here is the best way to set up your 389 or 421 to run on pump gas, a set of dished pistons. The one pictured below is for my 421, custom-ordered with a 26cc dish to drop compression all the way down to 9.05:1.
Another forged dished 421 piston, from RaceTec with a 23cc dish. The valve reliefs on this piston will allow the use of both early 20-degree valve angle 389/421 1966 and earlier heads (1.92"/1.66" valves) as well as 1967 and later 14-degree heads (2.11"/1.77" valves).
