base timing keeps advancing by itself...
Impatient ...or are you incapable.
It's been over a week!
Stranger? Lol
Hey guess what? You're the stranger around here!
We are generous enough to be giving advice to youuuuu!
Again, you are free to move along. Others have been very helpful, you have been rude. You can't ignore all previous information shared in the thread, give a shotgun blast of condescending generic troubleshooting instructions, and then get angry when I don't immediately ignore everyone else and drop what I am doing to follow your instructions, as you are A STRANGER who I do not know and do not particularly like. So kindly unfollow this thread and mind your own business.
To address the other poster's suggestions, some background info that may have been missed further up the thread.
1) This is a smog motor, recently rebuilt. Dished pistons, factory smog heads low compression build. It has been successfully running 87E10 since day 1, carb tuned to perfection according to instructions on this forum, the intent was always to run 87 octane. It has been suggested multiple times to just buy better gas, but that seems like a band-aid for a problem that can be fixed.
2) timing curve is custom, done by Ray, motor ran well for over 5k miles over a summer with no major changes to timing. 14 degrees initial, 22 mechanical with a fast curve. The problem began after storing over the winter and spring. Detonation from 2k-2500 under load, did not pop up right away but after a few tanks of gas.
3) ignition is pertronix gen 1 (simple magnetic trigger)on a points distributor with pertronix coil, bypassed ballast resistor. 0.040" gap. fires right up with ease hot, cold whatever and plugs stay spotless.
4) Dial back timing light is working properly, verified against timing cover marks at least up to 10 degrees.
I just put a fresh tank of gas in it from a different station then previously, will attempt to bump up timing a bit to see if that made a difference. It seems very possible that I got a really bad or contaminated batch of gas, with degraded octane content. I have pulled plugs several times, they are very clean porcelain no signs of detonation, about 2-3 turns of color and full ring of soot around fuel ring. I also am not allowing the motor to stay under detonation condition (it is only rattle under heavy load condition from 2-3k) so it is unlikely that it would show on the plugs.
Current leading theory is that the weakened distributor spring just exacerbated a problem that was already there (bad fuel or something else). Working on fabricating a piston stop to rule the dampener out (seems unlikely, no distortion on the rubber or movement). Already ruled out timing chain slop. Another possibility is heat. My temp gauge is not accurate (just had recalibrated by instrument specialties, still showing bottom range of cold when engine is fully warmed up) so i'm going to get a infrared thermometer tomorrow and ensure that the water temp is acceptable when the detonation rattle is occurring. Just in case thermostat has failed or some other heat related issue.
