Cylinder bores

You have little choice. Either fit new std rings or have a rebore complete with new pistons, rings, etc. The bores wont be circular, but that has nothing to do with the options available. Mike.

The very top of the bore (and the very bottom) doesn't get worn at all, as the rings stop just short of this. So if you clean all the carbon off you can then see if there's any wear - there will be a ridge if there is. Old rule of thumb was if your fingernail got stuck on the ridge it was time for a re-bore.

But if it needs a re-bore it will also need new pistons - not just oversize rings. If the bore is ok and you're fitting new standard rings use a glaze breaker tool to hone the bores first.

There is usally a ridge at the top but not at the bottom and one can check the difference by installing a ring at the top and bottom and noting the difference in ring gap. Proper action is to bore out etc and fit oversize pistons but you can bore out very slightly and fit new rings to the old pistons without much trouble. I've infact, simply fitted new rings without any other work to a couple of cars and had no problems whatsoever afterwards. You can get chamfered rings that will clear the top ridge.

You're going to have to take it to an engineering shop anyway because the bores need honing even if you're just fitting new rings otherwise all sorts of nasty s**te starts happening. The engineer should check the bore for ovality as a matter of course and advise you accordingly.

Rebores only become expensive when they're done to a size that requires oversize pistons.

You can hone yourself with a special tool and an electric drill. Never tried it myself as it's a long time since I've worn out an engine. As Rover V-8s basically don't if half looked after.

Same with the Pinto in my Laser. Apart from the camshaft lube issues, everything block related is pretty bombproof.

I've infact, simply

This works well on the old MA series Micra engines. 80K they burn oil. New rings and they last another 80K.

Ok thanks for the input but how about a real good honing and a set of rings instead of a rebore and pistons ?

Rich

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Chances are that a light hone and a new set of rings will give the engine another lease of life. It really depends upon how worn the bores are. You might even be able to get o/s thickness rings. A simple machining of the piston ring grooves to fit them, giving an even better result than new std rings alone. Mike.