used Grant chromoly rings on pistons that were cleaned by engine rebuilder, also had block honed, decked and cleaned. assembled engine myself, everything went smoothly and the car was running fine, now 200km later its blown a head gasket, so Ive removed the head, but now it seems pistons are a little sloppy in the bores also, i was starting to get a little blowby but i thought it might have just been steam from the bhg, question i have is what would cause the rings to fail this early! or should the piston have a fair amount of play already! cheers
morrisman1,
Sep 13, 5:07pm
did you measure the cylinders to ensure they are within what would be acceptable for the standard pistons!
rbjz,
Sep 13, 5:11pm
it was a low km engine around the 80ks, had a run bearing which lead to full bottom end rebuild,and i only had it honed so i didn't even think to measure the cylinders
morrisman1,
Sep 13, 5:14pm
Hmm may be worth checking. For all you know there might have been ten thou of wear.
rbjz,
Sep 13, 5:21pm
sounds like im taking the bottom end apart tomorrow, car wasn't blowing any smoke or anything tho, but i did think it might have been turning over quicker then whats normal, no oil coming out the breathers at all just smoke/steam.
rbjz,
Sep 13, 5:24pm
wish i done a compression test before i removed head!
elect70,
Sep 13, 5:28pm
Fit oil control rings ! , i usually do if not reboring.Or maybe they neverbed in properly .
movnon,
Sep 13, 5:39pm
seems to me no reputable engine rebuilder would hone a block with excess wear.Appears the rings have been incorrectly fitted apart from your head probs.
rob_man,
Sep 13, 5:48pm
Moly rings need a very well scratched bore to bed in properly as the Japs found in the 80s. I forget which maker had to fit new rings to a lot of cars but the recommendation was to abrade the bores by hand with 80 grit sandpaper before assembly.
snoopy221,
Sep 13, 5:55pm
question i have is what would cause the rings to fail this early! or should the piston have a fair amount of play already! cheers
Answer is [COMPRESSION]rings have NOTHING to do with the piston to bore clearance. The tensioner/scraperbetween the side rails on oil control rings can. The Q! IMHO is why did the head gasket fail!
wellabolla,
Sep 13, 7:12pm
Moly rings need a correct "moly ring hone ".once machined the bores need honing to suit chromoly rings.ya cant run them on a stock ring type hone thought ya engine builder would have known that
rob_man,
Sep 13, 7:20pm
You'd think so eh! did he know the rings were moly!
movnon,
Sep 13, 7:34pm
could be the jappa block cant handle the chrome moly rings!
wellabolla,
Oct 25, 8:09am
If a dirty old american iron block can handle them.a Modern jappa motor sure would.lol
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