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Who wants to take a guess at the CCs of dish on these pistons?

Discussion in 'The Garage' started by Russell, Dec 13, 2006.

  1. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

    Jun 23, 2000
    Likes Received:
    Fort McMurray, Alberta
    Hey guys!

    This is a pic of my TPI engine when I had it taken apart a couple years ago, long before it became TPI. I still have those same pistons in there, but with a set of smogger heads, and a camshaft that isn't particularly built for TPI.

    I'm wanting to swap a set of mildly ported swirlport TBI heads I just rebuilt on, with an 87+ TPI lower intake I am planning on buying, then porting and gasket matching with the rest of my plenum, and swapping in a new EFI camshaft in.

    I feel some money spent up front will make me far happier with the TPI system, and will save me a crapload of tuning time invested into the chip.

    However, before I switch from a set of 78cc heads to a set of 64cc heads, I need to confirm my thoughts that these pistons have indeed got at least 10cc dishes in them. With a standard compressible headgasket, and 64cc heads, and a 10cc dished piston, my compression ratio is about 9.3:1, which is still in the 87 octane range, right where I want it.

    I know these pistons arn't particularly the best out there, in that they basically eliminate the quench effect during compression, but they are what I have, and I don't really plan on taking the bottom end apart to replace pistons, cause then suddenly new heads and a cam is gonna turn into a total engine overhaul, and cost a whole lot more than I am hoping to spend right now, lol

    Attached is a pic :)

  2. MaxPF

    MaxPF 1/2 ton status

    Apr 13, 2006
    Likes Received:
    Chandler, Arizona
    Well, the 4 valve reliefs are usually around 6cc's, so with the shallow dish and chamfer around the edges you are probably at about 12cc's. Run it, and if it pings use a higher grade of gas :D

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