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Old 06-23-2007, 05:42 PM
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Measuring piston below deck.

I'm wondering what the proper way to measure piston below deck height is.

If i would like to achieve 0.005 in" below deck am I to Measure along the centerline of the wrist pin to eleminate error from the piston rocking in the bore. Or am i to measure at the edges of the piston rocking the piston on the wrist pin to it's highest point at both sides.

Also am i to do this with the piston rings installed during the Pre assembly checks or without the pisron rings.

I am trying to achieve a Qurnch of 0.040 to 0.045 with my gaskets compressed height.

I would just like to know the right way to do it so I achieve what I want for my quench height instead of only thinking that it's all measured up right.


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Old 06-23-2007, 05:55 PM
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Standing at the side of the motor, measure on the pin axis at 3:00 O'clock and 9:00 O'clock. Rings or no rings probably won't make that much difference. I do it without rings and sometimes wrap some masking tape around the ring land area if I'm building a motor with a lot of piston to wall clearance. Have a buddy put a long handle on a socket and engage the bolt on the front of the crank to rock the piston through a couple of degrees on each side of TDC so you get the smallest reading. Use a depth micrometer or the slide function on your 6" dial caliper. A measurement which is different from one side of the piston to the other could indicate a bent rod.
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Old 06-24-2007, 08:23 PM
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thanks for the info. My buddy is a machinist, just not the automotive type. we have all the tools we need so now it can measure it right.
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