OP as others have already commented you have a detonation problem caused by engine design choices you made, timing you chose to run and gas you chose to use. Some times the gas problem is unavoidable when you are on fumes. Better planning can mitigate this.
The detonation devices that are generally commercially available will only tell you after the fact that you had a problem — not particularly helpful but better than nothing. What you need is a detection and correction device that will detect the sonic signature of detonation at the onset of detonation and then in real time pull the timing for that just that one cylinder to save it before the next ignition event.
That I am aware of there is only one commercially available product that does this. It is called the J&S Safeguard system. In addition to pulling ignition timing in real time on a cylinder by cylinder basis it incrementally restores timing until it "hears" that detonation sonic signature again and then backs off just short of the detonation timing threshold.
I use the system with a coil on plug (COP) ignition 9:1 c/r, a screw blower with 18 psi of boost and 91 octane Kalifornia gas. I have no detonation. If you get the occasional bad tank of gas (as we all occasionally do) it will protect all the monies (and parts) you have in your engine.
To my knowledge it does not work with old point style distributor ignitions. It does work with more modern ignitions. This is the web site =>
J&S Safeguard. I just looked at the webpage and I was wrong. They do manufacture a system for distributor ignitions with points. It is their universal system.
They are not cheap (~$600 base system) but then again neither are engine parts — as you either will or already are discovering.
I persuaded a friend to put one on his twin turbo engine and his tuner was dismissive of the product until he made a mistake on the fuel and timing maps that sent the engine into detonation country.
When it happened the Safeguard lit up like a Christmas for all eight cylinders and the car immediately fell on its nose. No damage was done and when they discovered the whoops in the fuel and timing maps even the tuner became a true believer.
This device will pay for itself in broken parts you don't break — anymore.
Ed
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