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Dave,
I am not positive, but I do not think the deck height is .080. Mine was about .020 with flat tops. This difference, .060 is 1.5mm. I have not run the new figures for CR, but feel it is closer to the 11.5-12.0 range. Just Checking:)
Joshua L.
 

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I am running a stock Nissan L28 head gasket, I'm not sure how thick it is, probably 1mm. I am running special flat-pistons from an L18? I can't remember the part number, but they are Nissan Performance pistons from an L18 or L20, and they have a shorter wristpin to deck height to go with the 280 rods that I'm using. It took me forever to find the right rings to go with these pistons as I'm told that these pistons haven't been made since the late 80's.
 

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Re: With the pistons you have, you have a lower CR

> I am running a stock Nissan L28 head gasket,
> I'm not sure how thick it is, probably 1mm.
> I am running special flat-pistons from an
> L18? I can't remember the part number, but
> they are Nissan Performance pistons from an
> L18 or L20, and they have a shorter wristpin
> to deck height to go with the 280 rods that
> I'm using. It took me forever to find the
> right rings to go with these pistons as I'm
> told that these pistons haven't been made
> since the late 80's.

Chris,
That explains the radical difference in what some of us were calculating for your CR. With the L18/20 pistons whose wrist pin is closer to the top of the piston, you are not a what is called zero deck height, which we were using for calculations. Just as a quick example, if they are 35mm height, vs the ~38-39 mm height of the stock pistons, then you need to add that volume to your final volume in the calculations. Bottom line, my guess is you are at 10:1-10.5:1. Anyone who is at 11:1 with an E-31/E-88 is not really able to run pump gas. The chambers just aren't designed for it. Some people have it that high, but they are on the ragged edge of pinging, and that is with perfect timing. It leaves no room for error. With a chamber design like the P-series heads, you can run the compression up higher, and I have seen in the mid 11's on 93 gas. The design is more detonation resistant.
-Bob Hanvey
 
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