At Sacramento Raceway I think it was many moons ago we were running a Calif. Outlaw Pro Stock organization, basically pro style door slammers with Blowers &/or Smack, this guy Doc Finnley had a car that was Lee Sheppard twin P/S car , {i think it was} he was warming his engine up in the staging lanes after doing a valve spring change in the pits, I think it was, what I was told anyway, they used carb & brake parts cleaner on the inside of the valve covers to clean them out, the young kid helping them put the covers back on with out wiping them down, we were right next to the guy in the staging lanes, it blew the valve cover off the motor right next to me, scared the holly crap out of me, "I almost $hit my fire-suit I think", my next round/pass I cut like a 1.2 second reaction time/light instead of my normal 0.425-0.450 RT, I had bad nausea for an hour or so afterwords too... Everyone thought it was a N20 explosion but it wasn't...