compression check_shadetree mechanic style

[lurtch]

Hello fellow PagodaMen,

A couple summers ago I purchased a complete, recently running, M130.980. Now I am ready to migrate some of the parts off of it onto my Pagoda engine.

In order to verify valve seat condition without disassembly, I came up with this "head off" compression check method. Gasoline is the test fluid.

At the 21 minute mark all six leak-downs were nearly identical, and the meniscus had reached the spark plug electrode.

My gut feeling is that the test results were very favorable but I would still like to hear some some validation from our esteemed website team of experts.

Anybody want to weigh-in on this?



Larry in CA

[graphic66]

Don't know about your test, but I would get some marine aresol decarbonizing spray and clean the heads. here is the OMC version http://www.amazon.com/Johnson-Evinrude-Engine-Tune-Up-777185/dp/B001KYJAL0  there are many others like Yamaha decarbonizing aerosol etc. It will melt the carbon right off in no time.

[ja17]

Hello,

The fact that they all leaked down at the same rate, is probably a good sign that the valves seal well.  However the condition of the valve guides cannot be measured with this test.  The valve guides are most likely to causes you problems on a used head.

[Benz Dr.]

I have this engine that had a bent connecting rod due to hydro lock. This has nothing to due with valves and seats but in a way it does.
The power of just one explosion in an adjacent cylinder was enough to bend a very strong rod in a 450SL engine. There's enough power in a cup of gasoline to equal a stick of TNT. Knowing that, I'm not so casual with its use and generally don't even like to go near the stuff unless it's in a sealed container.
It's one of those things that we place ourselves near all the time without thinking about just how dangerous it really is. It's the leading cause of shop fires, burns and property damage so it should be treated with a lot more caution that it tends to receive.

I bought a vacuum tester to check valves and seats to avoid these risky methods. Although you can make gasoline work it's really not worth it if something goes wrong, is it?