[beautimus]

okay,
i'll take a stab at this one. if the engine has a bunch of miles on it, (if not, ignore this post) it could simply be carbon build up. to check for this, i usually take a soda bottle, fill it with water, and very sloowly dribble it ito the carburator while the engine is idiling. don't drop it in fast enough to kill the engine. just a few drops, then a few more, and so on until the contents of the soda bottle are all gone, then don't let the engine die on you and take it for a spin around the block.
the water in very small amounts will soften the carbon deposits on top of the pistons and allow them to break free and exit through the exhaust port. with the carbon removed your compression will be back where it should be, and the detonation should stop.
and you should be able to set the ignition timing properly.
If this is indeed the problem, it is because the carbon raises the compression ratio high enough that the engine can't run on the octane of your fuel. plus the carbon will glow hot enough to cause pre-ignition.
An old timer passed this trick on to me, when i was having problems with a camaro i owned, he was pretty smart, and in my case right on the money.
If this doesn't help you, i appologize. but maybe it will help someone else in the future so i threw the info out here.