Well, he asked valve and guide.
-To that end, Burch is on the right track, but missed the obvious. If the intake ports are full of liquid it will also leak past the guides and possibly the seals.
-The liquids I wouldnt use are water and laquer thinner. Water molecules are generally too big, and tend to stick together(vis a vis the miniscus in any glass of water).And the thinner will work too well seeping through the tiniest of openings, and its highly flammable.
- The liquids I have used are Kerosene, Diesel, and common parts cleaner Varsol/mineral spirits.Diesel is stinky. Kerosene is expensive. Varsol is the cheapest and is readily available. Of these 3 Varsol is the fastest.
-Do not even mention gasoline. I will figure out a way to cyber-smack you.
In a pinch Ive used a penetrating fluid, but it too goes through practically the tiniest of cracks.
-The trick is interpreting the results. I mean if you fill all the ports, and an hour later all the fluid is on the floor, how will you know thats bad? But if an hour later only one is down, now you have a basis of comparison. And again if an hour after fill up, all are down to different levels, which ones will you condemn?You see the dilemma?
-Once the heads are on the bench, its almost too late. Almost, unless you have a standard to work against . Lets say you had a fresh head, that was expected to seal 100%. So you performed a portfill test on it, and found that 2% (just picking an abstract number) of the liquid leaked out in say 6 hours; all the same. Now you have a standard against which all other heads in your shop can be measured; namely 2%/6 hours.
-And to check the guides using this same method, the seals need to come off and the springs back on.You would have to develop your own standard, empirically.
-And thats where Rustys answer is the right answer.
-And that brings us to mderoys idea. I used that method for years to determine problems with 2-stroke engines.Itsa very good method, and simulates well what goes on in a running engine.
-If you are unable or unwilling to have a machine shop evaluate those heads, either of these methods will get results. Whether or not theyre meaningful depends on your application and interpretation.But above all Rustys statement about the guides stands. If the guides are bad, by definition so are the the valve to seat seals.
BTW, where is Korsnas?