Thread: to bore or not to bore

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Hello,
I found out today the 390 in my boat has a cracked block in the #1 cylinder. I took it to the shop and they are going to sleeve it. I don't want to get another block because this one had some serious oil passage work by Kuntz and Craft back in the day. We checked the wear and it is only 5 thousandths in the other cylinders.

Should I bore it to .030 or not? I have gotten several opinions but nothing defining. I would rather not bore it to keep the costs down but will do what is best.

Thanks, TR

you can almost count on some shift, as for sleeves.....I would buy another block & save some money having it re-worked.

IF the .005 was just ring wear at the top of the cylinder. This is common in marine engines. You can just re-ring the motor. Use cast iron rings, not Chrome. If the out of round can be measured below the middle of the cylinder and you are getting excessive skirt to wall clearance. I would bore it.

Also don't let the fact that the motor has a sleeve in it bother you. A properly installed sleeve is stronger than the block it is in. The sleeves (most) are made of better material than the block.