"I have always built my own tester out of high quality
gauges and regulator and set the regulator for 100 psi
and used a small orifice between the gauges as i have
outlined. When i get a 2% on that method it is really
tight. I will CC John Goodman on this as well as his
forte is engine sealing and I am sure he will have
something to say that may or may not agree with this."
Not much to add, Dave. I would re-emphasize using an
orifice size equal to or smaller than ring end gap.
Supplying large a ofifice is common to most commercial
leak testers.
One other note on valve grinding. Seat and valve
concentricity is important to proper seal. Most of the
store-bought valve seat concentricity gauges do not
measure actual out-of-round. At best, most will
measure high and low spots on the valve seat. For a
better evaluation of seat roundness, one should
measure the intersection angles of the 45 degree (or
whatever you use here) seat and 15-30 degree top cut.
This intersection is what the valve face will see on
initial startup. Here is where light lapping will help
a bunch. It is very hard to machine valve seat
accuracy so light lapping will help.
It may also be a good idea to measure the valves
themselves (after grinding). If your valves are not
round and the stems are not straight, they will not
seal. You should try and attain a TIR of no more than
.0002". Check all those expensive new valves before
installation. Remember, these are a commodity item for
the supplier and can easily be damaged by the time you
get them. Don't be too upset if you have to regrind
them right out of the box.
John
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