piston slot

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    I am finally re-installing pistons and want to double check the piston skirt slot side. I don’t see anything in the spec data sheets and I only find a single note in the PASB’s for a 1932 model 54. Can someone verify, the piston slot goes on the left side away from the camshaft?

    It seems the logical way, but reviewing Motor’s manual it wasn’t universal.

    Thanks for any help.



    Hi Jim, you are correct. The solid side of the piston faces the camshaft. I have to visualize the rotation of the crankshaft, and the way the piston will travel when on the power stroke, The solid side of the piston needs to be against the cylinder wall that is taking the force from the piston’s efforts to push the connecting rod and crankshaft clockwise from roughly 1 o’clock to 4 o’clock.

    Greg Long


    Greg, thanks, I went through the same exercise reasoning the slot should be away from the thrust side, but curiously Packard did the opposite and I was wondering what I was missing. My ’36 Packard(with Egge pistons) has done fine so far (~20000 miles) with that seemingly backwards orientation. Now that I compare the original Packard and Pierce pistons they have a slight design difference that might explain. The Packard piston’s slot does not go all the way to the top of the skirt, Pierce’s skirt is completely slit. Where the Packard skirt is solid at the top I think corresponds with the highest side load when the piston tries to cock in the bore, so there may have reason to the madness.

    Thanks for confirming – now I don’t have to pull them all out and recheck bearings!


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