Some dubious calculations:

I tried pouring a tablespoon of water on some closed valves when the
head was upside down. At a depth of 0.25 inches water pressure is
0.01 psi and takes several minutes to run out.

ICE combustion gas pressure is 2500 psi, 250,000 times higher that the
tbls of water. This requires 1/500 the time, everything else being
equal.

The viscosity of water is 100 times greater than a gas so the time for
the combustion gas to leak past the valves is 1/50000 that of 200
seconds or 0.004 seconds.

At 3,000 rpm or 50 cycles/sec or 0.02 seconds the entire power stroke
will only last 0.005 seconds in a 4-cycle engine so I'll assume the
valve is ok.


Bret Cahill