Thread: timing chain troubles

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My 496 has broken several timing chains now and there is no obvious evidence pointing to the cause. Any ideas what I am missing ?

What chain and gear set are you running in it?

check the top and bottom gear with a strait edge ? you need to make sure they not running off set. i have check them have had to remachine the bottom gear to get them in line and run a thrust button on the front of the engine and drill with a .030 drill both the front galley plugs for add oil to the thrust and chain set this helps with air lock in the lifter galley if you run the hyd lifters and get the clicking i have never see or had any bust cheap or good set running roller engine with big cams

I have seen worn out and stretched chains, broken cam end, broken crank ends, broken gears, but I have never seen a chain break!
Pat

Originally Posted by HemiTCoupe

I have seen worn out and stretched chains, broken cam end, broken crank ends, broken gears, but I have never seen a chain break!
Pat

yes have a customer 427 that been line bored so many times that they do not make a line bore set to fit it used the cam correct to help with the chain slap.i could not get him to junk this block but still runs fine over 4 years like this with roller cam and is a drag car so it gets used hard

cam, lifters, timing chain and gears are all comp cams. cam is solid non-roller

Originally Posted by 1965ss496

cam, lifters, timing chain and gears are all comp cams. cam is solid non-roller

i had many sets looking at them side by side all are the same markers just stick it in there box and put there name on it .less it a steel machine gear set like rollmasters the iron gears like comp manley edel crane cloyes iron sets are all from the same maker or two thats about it .comp can sell bad stuff it happens but i think you have some alinement deal the china cranks and the old gm 454 blocks from the mild 70 had thick blocks but there machine work was less then good

Originally Posted by pat mccarthy

check the top and bottom gear with a strait edge ? you need to make sure they not running off set. i have check them have had to remachine the bottom gear to get them in line and run a thrust button on the front of the engine and drill with a .030 drill both the front galley plugs for add oil to the thrust and chain set this helps with air lock in the lifter galley if you run the hyd lifters and get the clicking i have never see or had any bust cheap or good set running roller engine with big cams

What Pat say's here is correct.
In every SBC or BBC I will drill a .030 hole in two of the galley plugs.
I would also run the best chain money can buy with steel gears and the oversized pins in the chain.
All chains stretch some but you will be closer with a good chain.
The way you build horsepower is in acurate cam timing.

my cam, lifters, timing set, keepers, retainers, and valve springs were all purchased together from comp cams. thier chain looks like junk, and has Japan stamped all over it.

my block is a 1980 gm 4 bolt truck block. it does not appear to have been lined bored to date. the cam does not walk too much, and to be sure, we put a button on it even though you are not supposed to need to with a solid lifter cam. my crank is a scat. i am not sure if it is from japan or china or what ? hope not. the gears appear to run straight, but the old gears have strange wear patterns since the explosion. i don't know if they were wearing funny, or maybe they were cut / machined that way , or maybe the junk chain caused them to wear funny? i only got 9 eighth mile passes on the complete rebuild, and i was shifting @ 6200. when the chain failed this time. the car usually goes through the traps in the quarter at @ 73, or 7400 . i just got a good set from cloyes, and not only does the chain look to be of a much better quality, but the gears appear to be machined correctly. i just hate to put it back together with the new chain if i am missing something. thanks for the help, and any other ideas you might have !

scat /cat/eagle /wheeler/ohio/ elgine/ cranks are china and more but saying that there junk is not true there is junk made in the US to most of the time they are a good value for a mild build to upper hp build .it appears it is ok needs to be check. it is a yes or no and if no good it needs to be fixed if you did not i would say thats were i would start .funny wear is from gears not running in line

Too much cam run out will cause one break, so install a cam button.