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  1. #1
    LTX Member


    Status
    Offline
    Join Date
    Jul 2020
    Name
    Jim
    Vehicle
    1996 Roadmaster wagon
    Location
    Minnesota
    Posts
    3

    Default Dynamic compression ratio

    Has anyone done any testing on various dynamic compression ratios in the LT1 gen 2 engines, particularly the iron head models?

    I ask because I have been finalizing specs for my new engine build for what is really a stock torque curve shape, but higher, type engine for my daily and cruiser RMW, 1996.

    Over the years, I have found the "rule of thumb" that says somewhere in the 7.0-8.5 DCR is where engines will make the most power to be quite true unless on racing gas, and along with never going over 8.5 on 91 octane, no ethanol, fuel also pretty good, but a little lower is better on less radical engines that build more cylinder pressure.

    My first run on the calculator with the custom built cam I had chosen came back at about 8.9 DCR on a 10.5 static, which was a very big surprise as the cam timing is pretty similar to stock but with fast ramps and higher lift. The stock engine runs fine on midgrade at 89 octane with ethanol even. To see what was going on, I ran the calculator on the stock engine at nominal specs most have measured and got 8.8 DCR. This is on an iron head (bad for detonation) with horrible quench distance at .068" (also bad for detonation). The only explanation has to be the reverse flow cooling keeping the heads cooler, as the rest is all normal style parts.

    Has anyone done anything that directly compares similar engines with and without reverse flow cooling to see just how much it will buy you in DCR? I have heard that it will give one point of static, but no testing to back it up.

    It appears to me, based on the stock engine being at 8.8 and having no issues with detonation, I should be fine with doing my proposed setup as it will also have quench at .040, which is tight enough to really knock down detonation.

    Opinions welcomed and desired.

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