07-04-2018, 04:44 PM
You’d need to take the pistons out to find out if they are R4 or not.
Really you should consider the state of the rest of the block. I’d be surprised if lack of power is caused by that score, unless it’s partially seized, too. If the other bores are ok, you could fit a liner to just that bore. I’d make sure I was using 3 ring pistons (no ring below the pin), and get them to fit a liner to just slightly more than the depth of the lowest ring. That way you preserve as much block strength as possible - the wall next to the crankcase flange will be very thin with a +80thou liner. It works, I’ve done it and used such a block for several racing seasons, and in the end it wasn’t that that failed. However if you need to do more cylinders I’d start to worry, at that stage a new block would probably be cheaper anyway.
Really you should consider the state of the rest of the block. I’d be surprised if lack of power is caused by that score, unless it’s partially seized, too. If the other bores are ok, you could fit a liner to just that bore. I’d make sure I was using 3 ring pistons (no ring below the pin), and get them to fit a liner to just slightly more than the depth of the lowest ring. That way you preserve as much block strength as possible - the wall next to the crankcase flange will be very thin with a +80thou liner. It works, I’ve done it and used such a block for several racing seasons, and in the end it wasn’t that that failed. However if you need to do more cylinders I’d start to worry, at that stage a new block would probably be cheaper anyway.
Alan Fairless