- Sun Feb 05, 2012 2:09 am
#9318
Hi there John R---You say you're doing "major work", with new mains and ---"probally some tuning work"?? At that level of engine dismantling it sounds like you're committed to a full overhaul--engine out , stripped, washed and laid -out for inspection ?? So naturally that will be including replacement seals, gaskets and the like. Irrespective of what year, milage etc what counts is what is in front of you on the bench right now. 1st}--Is the piston/barrel the correct one for the engine ie It's not some previous owners idea of the perfect special ?? Let's assume all is well on that score. 2nd}--What size piston is it ?? ie standard, +20, +40 etc. This should be a stamped No. on the top of the piston unless it is standard in which case there might be STD. or---nothing at all !!. In any event, the point I'm getting at is this-----If your piston is at the last overbore size then it really would be "cheapskate" if your measurements indicate that you might get another 2-3,000 miles, to put that assy. back in. Now on the other side of this coin----if you have a STD barrel/piston and you get similar readings , then a re-bore + piston to the next size is probally better. Dennis C has the right approach for the initial checks but as Anders F R found out it's not just about the numbers. Also--pistons are not round when new (expantion etc)-- Now then a new barrel over a half-worn piston-?? Do you REALLY want that for your lovely, painstaking re-build ?? Have you an engineering friend / machine shop/ evening class nearby--?? Ask them to pop a bore gauge down the barrel----3 readings in line with the gudgeon pin--3 at 90 degrees to it. Won't cost much and it will be accurate!!!!!! Finally------BE PATIENT. Whatever decision you take there will be a certain amount of running-in to do. Good luck and do keep us all informed of your progress.