the dizzy o-ring is probably crap. (maybe...its probably what your friend was talking about)
what year is your car and has it been replaced? mine was ROCK HARD and broke like plastic when removed...i had to cut/break it. its just one o-ring on the shaft housing of the distributor.... if it leaks it will squirt oil out and down the side of the head. include forward momentum of the car and it could run rearward as well and make a mess.
heres the TSRM diagram, its the o-ring pictured below the shaft.
http://www.cygnusx1.net/supra/library/TSRM/ig/IG_17.html
parts catalog view, number 19107A
http://www.cygnusx1.net/supra/library/EPC/MKIII_NATO/291410/1902_1.html
this COULD be the problem...not sure. its a cheap o-ring but you'll need to remove the distributor, paying attention to what position it's in before removal, and have a timing light avalable for resetting your timing once installed.
why are you removing the head? by dd you mean daily driving right?