Re: Detonation and preignition
Shard, you didnt mention that when you put the octaine booster in if it fixed the run on as well, which seemes to be your original complaint. so if fixed, ignore this, but if not, here's my thoughts on that topic. I'm aware that you suffer from detonation as well as running on, but ask yourself one simple question does my car detonate at idle? I'm guessing it doesnt. which makes me tend to think it might be something else like two problems possibly.
Your detonation happens when the heat and pressure inside the combustion chamber get so high so the petrol self ignites, this probley happens most under load i'm guessing, and since octaine booster helps there theres no doubt you have that problem.
But again, those pressures arnt there at idle, (timing dramaticly changes effective compression pressure when advanced). other things can cause run on or "dieseling".
First you could be running a engine at a hot temp, or could have a piece of material in your combustion chamber protruding out getting hot like a glow plug type affect, this could also cause pre ignition and might fit in with the pinging.
Or most common, is the engine dieseling simply caused by a high idle, please check this.
People with cams and hollys often drill holes in holley primary throttle plates to help in transfer slot action, check for this, together with a slightly high idle could cause problems.
True, crappy petrol can cause run on, but it would have to be really crappy and is usually accompanied with another problem like a high idle.
I used to have a mustang with a stock holly carb, the throttle plates where closed completely when the key was shut off via a anti dieseling soloniod.
It just doesnt hurt to check idle adjustments, if you need the high idle to go with the cam you might have to put a soloniod on. doesnt hurt performance,
To break it all down.. check the idle.
For the detonation problem, if your not using the car for racing now, and dont need the power, knock the total timing advance back for mellow street use.