Mine is a tie between crank bearing/bearing bore leak on a 575 and an intake boot on an 038 Super that had a hole in it big enough to swing a dead cat through...
I re-sealed a FS85R one time and forgot to put the case screws back in.
Living like that gets expensive fast.Guy had me put a topend on he said was a straight gassed 372 he had all the intake part's at his place i installed a meteor with cabers after cleaning the cylinder i told him to check the boot he didn't it was split 1/2 inch and a week later i put a 25.00 bigbore kit on it after he fried the meteor.
I hate those little tires. Tubes are yer friend