I have 2 sets of pistons, for my Pontiac 400 engine. One set has 4 valve reliefs ,and the other set has 8 valve reliefs. What's the difference ?
A lot, I would guess. One is an aftermarket set for a hot rod or racing engine..The other is a rebuilder or replacement item. Probably other differences too. Of course Lloyd is correct, given the limited amount of info ;-)
Loyd your math skills are amazing. Your really wasting your talent on fire fighting and pushing sand paper. And I don’t believe I’ve ever come across Pontiac 8 valve relief pistons. Pics or part number would help.
Nice try, but you forgot he said "set" of pistons. So, 8 in a set means 4x8 = 32(for 4 relief pistons) & 8x8=64(for 8 relief pistons); Then subtract: 64-32=32 Your answer is 32. @Lloyd's paint & glass gets an "E" for effort.
The 8 valve relief pistons were made for both early (389) and later model (400) valve angles. 2 barrel 67 400's had the earlier 20 degree valve angle like a 389. Every 4 barrel 67 400 and later model 400 (both 2 and 4 barrel) will use the later model 14 degree valve angle. Those 8 valve relief pistons are cast and sit way down in the hole and lower your compression. I have seen some that the edge is beveled on to lower your compression even more. They usually sit around .050 down in the hole. I would not use them.
Yep! The Ford high output 5.0L engines from '87-'91 were factory equipped with TRW forged pistons....
Nothing wrong with a set of 455 L2359 TRW forged for a street or Bracket engine. They are 4 eyebrow, multi-directional , of course. Don't know the 400 number, off hand.