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  1. #1

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    Installing new CP pistons... ring config?

    These pistons/rings aren't marked well; no arrows, no dots.

    I've got it figured out that the piston side with the smaller valve reliefs go toward the exhaust side... check.

    I think I've figured out that the copper-colored ring is top (and the number imprinted goes up?)

    The grey steel ring is second, and I know the side with the ledge cutout around the edge goes down.

    My question concerns the bottom oil rings... there's a tab that sticks up at the end of each; am I correct to assume these tabs face inside towards the expander ring when inserting into the piston?


    Also, any opinion on filing the rings? My bore is +0.010 at 3.948, and so was going to gap the top ring at just about 0.020. Should I leave a much bigger gap in the second ring? (the bottom oil rings don't need filing).


  2. #2

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    I was told the CP logo underneath goes toward the exhaust number up and ridge on second down .20 should be fine on first I think 2nd should be ,005 bigger

    http://www.cp-carrillo.com/LinkClick...Ls%3D&tabid=83

    Try that - good luck

  3. #3
    West Texas RXP skoepp's Avatar
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    What did you out ring gap at?
    what us everyone else setting there's at?

  4. #4
    Nothin' better than Doo'in it! BigDaddyRXP's Avatar
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    Quote Originally Posted by skoepp View Post
    What did you out ring gap at?
    what us everyone else setting there's at?
    CP recommends that bore size x .0055" will determine the top ring end gap on a boosted engine. So in his case 3.948 x .0055 = .0217 roughly .022" Second ring should be .004" to .006" larger.

  5. #5

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    Yeah, I aimed for .021 on top, and .023 on the middle. The CP rings did not require a lot of filing to get right; most were nearly right on the money.

    The rings were easy. The parts of this rebuild that had me cussing like a madman was installing the piston wrist pin circlips, and getting the pistons in the cylinders. I have a ring compressor, but it just didn't work well. Ended up bending an oil ring, and had to wait on a replacement. CP recently bought a company who invented a better wrist pin circlip which installs easy, and they tell me future pistons will start shipping with that, but I had to deal with their old ones.

    I started it for the first time today! I spent all day getting it back together. Needed a thick shim on one side to align it correctly; I had always thought I wasn't aligned perfectly from the factory. That's a scary moment, starting the engine after such a long rebuild. It ran well (only near idle at the ramp, so far) , but got a p1116 overheat after a few minutes. The problem... I put coolant in, BUT DIDN"T BLEED THE AIR BUBBLES OUT! The hoses are on the thermostat correctly, so I'm 98% that once I bleed the system, it'll be fine. I ran out of sun before I could remedy that.

    With the Riva ECU, Bosch 48#s, new Walbro and the fuel pressure set at 58#, the idle AFR was bacon rich at 10.5. I dialed my RRFPR down to 35# to get idle at AFR 12.5. Next, I'm installing a BEGi, so we'll see if I can finally get the fueling right at WOT.

  6. #6
    Eastside Powersports Slow 91's Avatar
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    Good to hear Scott. The CP wrist pin clips can be a PITA, until you get used to them.

  7. #7

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