I've got this little knock/ping problem with my a14 datto motor. I only noticed i had a problem after i bought myself a timing light. After checking my timing I got quite a shock cause my timing was set to 5 degrees ATDC I though to myself well this explains allot and set it to 5 deg BTDC. Only to discover that if my timing is set to where it is suppose to be I experience some major knock under the slightest throttle.

So i set my timing to TDC in the hoped that it'll be drivable, and it is, up until the point where the engine heats up properly then the lovely sound of destruction returns

At this point I was pretty sure that it was carbon on the sparkplugs(cleaned them and no change) or in the combustion chamber but another factor came into play. I bought a pressure tester just to make sure that its not the compression that's to high. The results are scary, I got an average pressure of 1425kPa on each cylinder and its suppose to be 1245kPa .

So, if my compression is too high won't it knock when the engine is cold as well?
If I need to drop the compression using a copper gasket, how do i work out how thick it must be?