1968 H/O vs. 1970 W30
#41
thanks. That’s also the minimum. You’ll find if you actually cc the dish it’s more than that. It’s a cast dish, not machined.
But let’s take that number anyway. what was the thinking on dishing the piston starting in 68 when the 67 was flat and had the same 10.5 rated comp ratio and the same cubes?
there is no argument they dished the piston for a reason. The 67 C head was 80 +/- and 10.5
any explanation?
But let’s take that number anyway. what was the thinking on dishing the piston starting in 68 when the 67 was flat and had the same 10.5 rated comp ratio and the same cubes?
there is no argument they dished the piston for a reason. The 67 C head was 80 +/- and 10.5
any explanation?
Last edited by CANADIANOLDS; July 9th, 2021 at 12:22 PM.
#42
thanks. That’s also the minimum. You’ll find if you actually cc the dish it’s more than that. It’s a cast dish, not machined.
But let’s take that number anyway. what was the thinking on dishing the piston starting in 68 when the 67 was flat and had the same 10.5 rated comp ratio and the same cubes?
there is no argument they dished the piston for a reason. The 67 C head was 80 +/- and 10.5
any explanation?
But let’s take that number anyway. what was the thinking on dishing the piston starting in 68 when the 67 was flat and had the same 10.5 rated comp ratio and the same cubes?
there is no argument they dished the piston for a reason. The 67 C head was 80 +/- and 10.5
any explanation?
. Many people did use factory style forged pistons, so, the spec was needed for those pistons. Oldsmobile supplied to NHRA specs shown below. You should note the 75 CC's minimum for all 400's except the 67 W-30 OAI which uses 71.9 CC's.
#44
#45
#46
woops. not sure what I was thinking earlier. I have nothing else other than some guesses. Seems like at least by 1970 they were most comfortable having actual production compression ratios at <10:1.
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