My Method of Removing Stuck Pistons
607 SE County Road 234 Gainsville, Florida 32641-1303
I’ve read with interest the many methods submitted to your
magazine for removing stuck pistons. I’d like to add my own
experience with a 4 HP Mogul engine in hopes that someone might
benefit from it. The engine had been sitting out in a pasture for
over a year with the head off and at such an angle that water was
trapped in the upper two or three inches of the exposed cylinder
wall. This particular model had an inspection plate on the rear of
the base that allowed me to release the connecting rod so the
cylinder and hopper could be removed and worked on as a unit. After
making a wooden saddle and clamping the unit to the workbench, I
removed the rusted studs and replaced them with new ones. Next, I
cut a series of 1′ round oak blocks, just smaller than the
cylinder diameter and also cut a 1/4‘
steel plate slightly larger than the head. Using the head as a
template, I marked and drilled six holes
1/64‘ oversize for the studs. Then, by
inserting enough wooden blocks to insure a space between the top of
the block and the bottom of the steel plate, I threaded on a set of
coupling nuts for maximum thread contact. I began to tighten the
nuts moving from stud to stud in a clockwise fashion. I went around
and around the studs, creating a spiral pattern of force until the
piston was finally free. At times I was able to turn individual
nuts only five degrees before moving to the next one. I didn’t
use a torque wrench, but instead went by ‘feel’ when
deciding how much to tighten each nut. I also waited at least 30
seconds before moving to the next stud, tapping around the
perimeter of the steel plate in the meantime. After the piston was
past the worst area I was able to take several turns per nut,
though it drove hard until it was completely out. The piston was
easy to salvage by simply cleaning after the wrist pin, rod and
rings were removed. The rings had to be chipped out and measured.
They were ordered from the Superior Piston Company and fit
perfectly after notching for the groove pin. I took the block to
Central Motors Machine Shop to be bored and sleeved by Lee Baker.
He did an excellent job and gave me a friendly reminder not to
forget to drill the piston oil hole through the sleeve! After total
re-assembly it was very difficult to turn the engine over unless
the compression release cam was engaged.
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