I'm claying my domed pistons for clearance and wondered if it is common practise to cover the whole dome in clay or different points of the dome. The last time i did this was with my old six pack pistons when i fitted my 76cc eddy heads, so not much clay was needed to fill the valve reliefs.
This time i may have got a little heavy handed with the clay and couldn't compress it, so i've taken the heads off again and i'm going to roll it a out thinner and try again.
Mick

I just did mine last week and I just rolled strings of clay about .250" diameter and strung them (four lines) over the valve reliefs, from one side to the other.
Brian

Thanks, that's what i was thinking of doing, just wondered what others more experienced than me did.
Mick

I just did mine (flat tops).. just rigged a dial indicator for it, put check springs on, and pushed the valve down till it hit the piston for every 5 degrees of crank rotation where it was going to be close, i.e. not at BDC..lol.

The clay method helps on checking the lateral clearances, edge of valves to the edge of the valve reliefs. That needs to be known I have had several motors that did not have enough lateral clearances to the valve reliefs once the motor was warmed up and driven BTW, 1/8 string of clay works good across the valve reliefs and anywhere else your worried about