Possible issue w Detonation. Cracked several pistons in land between compression rings. After new pistons installed want to make sure timing is right. On multiple Rides I’ve had E-Dist’s w no vac. Advance. For initial timing I’ve always timed the same as stock Dist’s w vac adv. using factory recommended for the engine. I’ve always thought til this issue that was good because vacuum vertically is gone as E-Dist. reaches 2500-3000 rpm preset advance is fully engaged. Thoughts?
Before you even think about timing, make sure that #1 top dead center on your dampener/balancer properly aligns with zero on the timing tab. Most engines do not. .bjb
you need to set your total timing at the rpm it is "all in" at, usually 3000 rpms with a timing light with a degree dial (adjustment) on it. Rev it to 3 grand and adjust the dial until you get the total timing you want and turn the dist until the mark lines up to the zero. Total timing for a street car is typically 34-38 degrees. depends on compression, gearing etc. If your car is truly detonating you should hear pinging on acceleration. retard until the pinging is gone. One question, what the heck is an "e-dist"
While heads were off I physically put #1 piston top of stroke w Dial indicator & remarked the balancer w white. Someone had put a file or chisel mark that lined up perfectly. Just needed white to see w Timing light.
On the cracked/broken ring lands and broken rings. Did you by chance put new rings in the engine and hone the cylinders but did not cut the ridge at the top out? You or who ever you got the engine from? I've had a couple of "we put new rings in and now it doesn't work" engines brought to me that they replaced The rings in and ran a ball hone though the cylinders but didn't cut the ridge out and the new compression ring jambed into the ridge and caused quite similar damage. With detonation you are going to have eroded spots in the top of the piston (s) and when it gets to the rings it usually leaves somewhat of a burned channel down the side of the piston. Cause for that is usually bad timing, or more often or not gas that isn't up to the compression ratio. As in when your buddy drives your car with the 11.5 compression and puts in the cheap regular when he puts gas in the tank before bringing it back. Had to dump a can of octane booster in one ride years ago after a buddy filled it with regular rather than premium. Luckily I caught it and made it to a store that had the octane booster.
I had engine built by a reputable shop. Sells or u can contract builds or rebuilds. Engine had only 2000 miles when started pushing smoke thru oil input neck in a puf puf puf pattern but no smoke in exhaust. Also showed bad compression in one cylinder. Cylinders looked good, no damage & still no ridge in top of cylinder, also so few miles cylinder still have honing cross hatch. No eroded marks on top of pistons but were dark as were head firing chambers.
Did the pistons crack after the build "by a reputable shop." How about the puf-puf and the low compression ?
Seemed to run fine to that point. Good compression & no excessive crank case blow by. Usually run hard before putting away for Winter. This time issues occurred after that final run before putting away.
Finding TDC with a dial indicator is a crap shoot. Piston is in dwell for too many degrees. Piston stop is the precise method. Might not have been your problem, but use the piston stop next time around.
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