Best fluid to see if the valve/seat are sealing well

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Lapping compound. No need to check with any fluid when you lap them in properly and SEE the SOLID grey line on both the seat and the valve face. Works every time, 100%.
 
not water, the molecules are too big, and clump together by surface-tension, sticking to the surfaces like magnets.
Not alcohol, the molecules are so small they will creep by capillary action, thru almost anything.
That leaves gasoline, but you know, don't burn your shop down.

I use alcohol when I want to show a customer how lousy the valve job is that he got done somewhere else. It does what gas does, but is faster.
 
We always used solvent but we had 5 gallons sitting around. It doesn't evaporate as fast as gas or alcohol. You can but mineral spirits by the quart many places. Hardware stores and big box stores have it in their paint departments.
 
Pull vacuum on every port. The most accurate way . There is a tool for it with an electric pump. I watch steve do it on every head that leaves after they are done.

Nothing is thinner then air. Its not flammable and its free. LOL
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RustyRatRod said:
Lapping compound. No need to check with any fluid when you lap them in properly and SEE the SOLID grey line on both the seat and the valve face. Works every time, 100%.
Click to expand...

I only check one intake and exhaust per head, if I do the valve job, just to verify all is what I want and where it should be.
 
You can also use a hand pump they are cheap at Harbor Freight . You just need a plate with a fitting in the middle.
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When I worked in a machine shop in the 80s we use to spray WD-40 & blow compressed air in the port. Popping the valves to insure proper seating in the center of the valve face was always crucial.
 
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