I blew an HG last summer. I was running 23PSI and 26 degrees of timing with 116 Sunoco racing fuel. The HG let loose pressurized the crankcase and pumped oil through the dipstick and valve cover breather. The blue smoke was quite impressive. This was at mid track...I limped back to the pits...looked at the data in Turbolink and didn't see anything that indicated that it detonated. There was 2 degrees of ignition retard shifting between the gears, but nothing more. Mind you the computer updates every 1.5 seconds, so it may have missed the"event", but I don't think so. I think that the cummulative abuse of 13 years finally took its toll.