best "clay" for checking V-P and other combustion chamber clearances.

[Dan Timberlake]

I know some folks insist dial indicator measurements are the best way to quantify "real" Valve to Piston clearance, but I see clay or some other non-springy squishy substance being a good way to check for valve notch angles, valve notch centering, piston to head clearance, and etc.

I'm actually going to be using "clay" for an industrial clearance check, and wonder what folks have found to be good products and techniques in terms of non-return squishing for accuracy, ability to compress down nice and thin, not too sticky, and anything else.

thanks,

Dan T

[Ericnova]

Good old fashioned non drying modeling clay.
https://www.walmart.com/ip/Sculpey-EZ-S ... h/19212226

I think Crayola is the same thing, but have not tried it.

Avoid Silly Putty and Play-Doh type materials, too springy.

[Promodwrench]

Sculpey modeling clay is the best thing I've used.
When it's new sometimes you'll run into it wanting to stick to the valve a little. You can put a tiny amount of talcum powder on your hands then knead the clay as normal and this will stop any sticking/tearing of it. Hobby Lobby and Michael's always have it in stock.

[Jagdpanzer]

Auto detailing clay bar

[DCal]

I use modeling clay as well as indicators because, as mentioned, it's great for verifying radial clearance. Clean the piston with acetone and put oil on the valve head. Cut the clay with a razor blade so it won't push the clay upwards.

[jake197000]

x2

[hoodeng]

Like others, i have found Plasticine to be one of the best, but there is a trick with that stuff, the older the lump that you use for testing the better it is at defining what you are looking for.
Mine would be that old it probably started life 30 or more years ago,but it is a bit like pop's axe ,,,two heads and four handles later. I bought a pack probably ten years ago to top up the lump that is in use .In summer it is just right, in winter i pound it on the vice with a hammer to get it where i need it. Keeping the new stuff in the fridge helps it age.
The white stuff is Elastosil ,very handy for making port and chamber molds, less than 1% shrinkage after setting. Great for accurate molds of combustion chamber voids if you are getting custom pistons made, or if you want to record a port.
Cheers.

[geraldtson]

Plumbers putty.

[jake197000]

i put a very light film of oil on the piston and valve so clay dont stick then it pulls right off

[Leftcoaster]

Resin core solder is available in numerous diameters - - 0.040" piston to head clearance needs 0.050 to 0.060"d solder, preferably 60/40 lead/tin or equivalent, available from hobby electronics shops

Valve to piston clearance may need thicker solder from hardware stores etc - - be sure to first measure piston rock with a dial guage, then allow for it after the solder has been squished

[af2]

Radial clearance needs clay all the way around the valve. Going to be doing this next week. PIA but the only way I see.

[hoodeng]

lube the valve only and keep the piston clean so the Plasticine does not lift off and holds firm to cut.

The reason the piston in my photo looks lubed is it was greased around the bore to CC.The crown was cleaned with thinners before the TDC check.

Cheers.

[Schurkey]

Plumbers putty.

X2. Cheap and simple. I have been known to put Saran Wrap over it to prevent sticking. Sometimes that works really well...sometimes it screws up the impression. A ball of plumber's putty on the oil pump pickup, some Saran wrap over the top...put the pan on, take it off, check for clearance.

[MadBill]

Resin core solder is available in numerous diameters - - 0.040" piston to head clearance needs 0.050 to 0.060"d solder, preferably 60/40 lead/tin or equivalent, available from hobby electronics shops

Valve to piston clearance may need thicker solder from hardware stores etc - - be sure to first measure piston rock with a dial guage, then allow for it after the solder has been squished

I too use solder at a single location, but I'd be worried about using a half circle of it in an app like af2's below, especially with sub-8mm valve stems, as the required force might be excessive...

[Kevin Johnson]

https://www.riogrande.com/product/BulkE ... lsrc=aw.ds

Sprue wax might work better than solder. It is the wax used to attach patterns to a base for casting.