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  1. #1
    Join Date
    Mar 2009
    Southern Maryland

    Compression height and rod length

    Help me gain a better understanding of compression height. I understand what it is and how it's calculated. Let's say the application is a Ford 4.0sohc v6. The bore is 3.953, the stroke is 3.31. Rod length 5.748. Deck height is 8.858. Rod journal is 2.125. Compression height is 1.44

    So I'm think about strapping an m90 (or m112) blower on this motor. It has a crummy aftermarket. So I started digging and found that 3.95 and 3.97 are common Mopar 318 bore sizes. 318 stroker pistons are available at 1.46 compression height. Chevy rods 5.7. that's pretty close. As close as I can get without custom parts which would send me in a differemt direction. Digging a further, there are other 318 pistons 1.71-1.78 in compression height.

    My question is, that if I add rod length and piston compression height and keep that very close to stock, can i use shorter rods and taller pistons as long as I don't deviate much from that stock measurement? I am trying to gain forged rotating assembly and lower compression without expensive custom pistons

  2. #2
    Join Date
    May 2020
    My general take on it. A taller compression height piston will be stronger and support the bore more, though heavier to move.
    There is only short term plusís from cheap skating.
    Plan, save and spend on what you really want.