Pistons specs question for 340 build

33IMP said

My 1989 TRW catalog shows a 2295 dome piston as 13.1/12.1 cc. No plus or minus.
It shows a 2266 as "flat head" (no cc rating) cause its a flat top with no reliefs.
It shows a 2355 (six pack, four relief flat top) as minus 7cc.
It shows 2399 (my 454 chevy piston, small dome, with an exhaust valve relief) as 13.8 cc. (No plus or minus)
All of these are in a column marked "effective dome volume".

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And that's correct. What's getting lost and dazed and confused is, we're talking about two different things. Piston volume is not the same as chamber/cylinder volume. That's where the problem is.....and it should never have been measured like that. They should have measured pistons in the same manner as chamber and cylinder volume, but somewhere along the way somebody glommed up the works tryin to be "smart".