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I have the engine down to the block and inspected it. The cylinders don't look too bad at all. Do I still have them rebored or just rebuild the engine with new parts?
 

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clean it with fine steel wool to remove the blackness.
Go AROUND the ridge only ( not up and down) to prevent compression loss.
If there is a metal ridge big enough to catch a thumbnail in, I always bore it.
You MAY get away with using a hone on a drill
to clean it up sufficiently.

The ridge has GOT to go.
Carbon buildup on that ridge and the sharp edge itself can burn red and cause preignition and poor power.
 

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Pits just hold more oil.

Seriously, spend a few bucks to have your friendly local machinist measure the bores. Find out if the taper is reasonable, and how your piston-cylinder clearance is going to look.

I think sealed power makes a 4.130 piston. I know they make a 4.140.
 

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What ibarbuckle said. Have the bores checked for taper, etc. If ok, hone and go. Every time you bore an engine, you shorten its life. A Ponitac is good for only .060" over before sleeving, in general. Especially the 389's. Overbore as little as possible, and have custom dished pistons made to insure drivability on today's fuels. If you can get by without boring, go for it.
 
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