modeling clay

do you guys have a particular brand or style of modeling clay you use for valve clearances? synthetic, natural, hardening, non hardening?

Play-doh from your kids toybox. After you make a little pad and stick it to the piston you can put a light coat of oil on top to help it not stick to the valve.

If you've ever actually used play doh you got extremely lucky. I can tell you from personal experience it definitely will not work. 20 some odd years ago me and my dad dropped a valve in a 460 and totally trashed a freshly ported dove head and forged piston. After much head scratching we decided to conduct an experiment. The play doh that we stole from my nephew was somewhat fluffy. It is not dense enough to use for gauge purposes. The only reason we used it in the first place was our clay had gone hard and my dad had been chasing the kid all week trying to keep the play doh out of the rug. It saved us a trip to town alright.

Plumbers putty works pretty good, easy to get at Menards
Seems to stay soft for along time in storage

Kid's modeling clay. Get it at the toy store or hobby shop. I agree about Play-doh. Not the best stuff. It's better to set up a dial indicator on the retainer if you can. If not, clay works. The denser the clay, the better the results will be.