Hello Boys.... another year upon us!
Thanks for comments and suggestions from ALL of you back in Nov/Dec. You will recall that I'd blocked off EGR on my '80 Bobcat some time ago (see other thread if you want..), and it had resulted in bad pre-ignite under any kind of load. Not helped by Premium fuel nor even octane-boost!
Over last few months I tried several of your suggestions... playing with timing some more, de-carbonizing, and also tried pinto_one's intriguing recommendation of adjusting the spring inside advance can...but all to no avail, alas!
But then...
About a week ago I decided to recheck and play with the vacuum lines (plus the car had started to run really poorly last couple months...no power, pronounced hesitation at cruise and take-off, etc..). Rather randomly I BLOCKED OFF carb's vac-port you see in center of photo (port for vac-line pointing off to the left, hose has that valve canister and goes to thin yellow line....which goes down, I believe, to big vac-junction near front of block).
Thereafter, took a lengthy 100+ mile drive (actually drove to a friend's to rebuild front brakes!).............. ....and....... VOILA!!.....NO MORE ping, even under very hard driving.
Not sure what I've disconnected or bypassed, but happyhappy. I suspect this is an emission-related port (??..do we know, Gents..??). At any rate, the ol' Girl is now being weened OFF Premium, and I'm getting the rosy feeling that the further I get from 93+ octane, the better the car's running.
Still testing, but my idle-miss is almost gone and lack-of-power improving a lot too. Trial and error scores again, and/or...
"Oh what a difference a golf-tee can make"....
My conclusion is that I probably had a significant vacuum leak ever since I bought the car, leaning things out, and the EGR elimination didn't help matters, causing the nasty pre-ignition, but watcha think of my "fix"??
Anyway, for the moment at least, it seems the Ping is a Thing of the Past... hopefully!!
Cheers, and have a good week, Kids!