Re: max overbore
Hi 1930,
Do not know all of your existing engine details, existing cylinder measurements, & engine history; however, FWIW, I had a .125 bore on all (4) cylinders when I recently bought this last Model A.
Engine previously ran with only non-detergent oil & created such a sludge mess throughout.
Removed old (4) pistons & rings, honed cylinders, & provided new .125 pistons & new .125 rings after seeing hardly any ridge & after checking bore diameter throughout with telescoping gauge.
Does not smoke, uses no oil, lots of compression, & with new full flow oil filter & Hi-Boy K & N Air Filter, it will certainly outlast me with 5W40 Rotella Oil.
Years ago with non-detergent oil not changed regularily, ring grooves got clogged with non-detergent sludge -- then rings began to stick in ring grooves & not expand -- with piston up & down speed, rings got pressed in at smaller diameter lower ends of cylinders & could not expand fast enough when they reached larger diameter tops of cylinders; hence lost compression.
Years ago thousands of engines were very successfully fitted with new pistons & rings without re-boring.
Even though engine manufacturers always write very critical specifications on when to re-bore, please remember that manufacturers also have a marketing department & stock holders, always hoping that they can sell as many oversized manufacturers parts as possible, as well as dealerships wanting to get their share of oversized parts & labor sales & profits.
Maybe your existing .125 cylinders are possibly not too worn to require re-boring.
If not already done, maybe check them out.
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