Jim, my engine says the same thing yours does. Real 100 or knock or retard the timing. Even with the static timing at 6 BTDC (reducing total timing to 30 degrees) all it takes is a good stomp to start the knocking.

My pistons are probably beat to heck as I can't get the fuel I need locally. When Pontiac built this engine with "10.75:1" compression which is actually around 10.25:1, 72cc chambers and tall flatttops, they were not anticipating low octane unleaded, and my car has not changed with the times.

Z_Firebird, your lower compression 10:1 pistons allow you to run lower octane without detonation. Bjorn's lower compression cylinder heads allow him to run regular unleaded with full timing and get better power than my 'bird can with all the timing taken out. I've ridden with Bjorn, so it's not speculation.

I have a set of heads and a block and crank but not enough parts yet to build a street engine. I want to keep my numbers-match dinosaur untouched.