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Cylinder Head Leak test (water VS gas/alcohol)

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7K views 8 replies 5 participants last post by  mossin_90  
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#1 ·
This is a 2-part question...for anyone who has done their OWN head work. I'm in the process of hand-lapping the valves on my HF (thank GOD it's only 8 valves). What a PITA! I'm trying to be as meticulous as possible with the cleaning of the valve and the oil on the valve stem while I'm lapping it..and the valve grinding compound on the valve seat, etc. But each time I think I'm done, I re-clean the valve and re-install it in the head ONLY to have the leaks show up again when I perform the little leak-test-trick (filling the intake/exhaust ports with fluid and then waiting to see if it starts weeping at the combustion side of the valve).

Part 2: Even if I can get just ONE valve to hold water during this test, NONE of them seem to be able to hold back gasoline (if I use gasoline instead of water for this test). Yes, I realize water is going to be larger molecules, which is why its holding. Just want to know about the gas/alcohol. Can anyone confirm whether or not water is a good enough test, or should the cylinder head also be capable of holding back gasoline (or even alcohol)? I just want to make sure it's right before I put it back on the car...and if I give up I guess I'll just have to call myself incapable - and just drop it off at a machine shop. Jeez! I was hoping to be able to do SOMETHING with this rebuild on my own.

Thanks for any/all help.
 
Discussion starter · #3 ·
lol - yes. In fact, that's my latest item of question. I'm wondering if these little weak HF springs are in question...as I have heard that the HF springs were weaker/softer to allow for better fuel economy (by way of less energy required to exercise them). Still not even sure if that's part is true, but I do know that the Haynes manual for this car has a different spec for the unsprung valve spring "free length" specific to the D15B6 / HF engine for both the intake as well as the exhaust valves. So at least I know that the HF springs are different than the DX & Si springs.

But to reiterate, "yes", the valve springs have been reinstalled in each of the cases where I have leak tested herein.

Any ideas? I went out there again and re-lapped the same few valves even a 3rd time. The seats look very good to my novice eye...but those bastards still leak when I fill up the ports with water and walk away for more than a few minutes.
 
Discussion starter · #7 ·
Thank you all. I will heed your advice with the higher mileage HF heads & blocks that I have. However, I'll be shocked and disappointed if this particular 120K-mile HF head (the one in question) really winds up in need of new guides...but I will at least have the stem-to-guide clearances measured at a shop on this one.

My other HF engines made it into the high 200's without needing this. It's just that lower (120K) mileage engine should really be able to go a while longer without needing a rebuild IMO. This engine sat tucked away for so long that I just couldn't try putting it into service without pulling the head off for a look.

Again, much thanks for the advice
 
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