If there's enough ridge to prevent the piston from coming out, there is a distinct possibility of enough taper wear in the cylinder to prevent a successful re-ring job. Many auto parts stores will rent you a reamer with a refundable deposit equal to the purchase price of the tool in case you decide not to return it. Once you ream the ridge, measure the cylinder taper by putting a piston ring into the top of the cylinder at the top of the ring travel and measuring the gap with some stacked-up feeler gauge blades. Then push the ring to the bottom of its travel with a piston to keep the ring square with the bore and measure the gap again. Subtract the bottom measurement from the top and divide the result by 3. The result is the cylinder taper in thousandths. If it has more than 5 thousandths of taper, don't try a re-ring- - - -rebore the cylinders and install oversize pistons.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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