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DIY Guru
96 Ranger-stock
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Discussion Starter #1
How to fluid test a cylinder Head


This is a simple and quick way to check for seat and valve seal.

First clean the head by the method of your choosing.

Once the head is cleaned, blow the runners out with compressed air to remove any carbon, oil or crud that can give a “false” seal.


Next lay the head with the runners up, and the valves facing you. I am starting on the intake side.

Now get a jug of fluid, I am using water.


Now here is the hard part….. Pour the fluid in the runners, one at a time.

Now that all four runners are filled with fluid.

Now look at the valves in the combustion chamber, no fluid. All is dry. This side is good and the intakes are sealed well.

Now flip the head over, and fill the exhaust runners.

Take note that you will have to plug the EGR passage so the fluid will stay in the runner.
 

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DIY Guru
96 Ranger-stock
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637 Posts
Discussion Starter #2
Look at the fluid pour out past the valve, there is an issue that needs to be looked into. It is a bent valve.

Notice how the runner on the left of the divider still holds fluid, but the one on the right is empty. This is cylinder #4. If the left side will not hold fluid, check to make sure you have blocked off the EGR passage.


If you used water, blow the excessive water out with compressed air.

Then with WD-40

Spray WD-40 in the runners to inhibit rust formation on the valve stems.


Now at this point any valve sealing issues can be addressed and fixed.
 

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man I did this with my head and had like 5 bent valves. I said fuck it and installed that head and its been running till this day on 3 separate blocks. I think if it leaks so little the heat will make it seal when its running
maybe im wrong though but I get great compression numbers on a hot motor
 

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DIY Guru
96 Ranger-stock
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637 Posts
Discussion Starter #6
V8, I would say you had a touch of carbon between the seat and valve, that would be just enough to let it leak a touch. Once you bolted it on the valve hitting the seat crunched the carbon and the valve got a full seal
 

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folks back here use wd40 or solvent to check valves and seats AFTER machining - if it holds penetrating liquid for 5 to 15 minutes - it is good )))
ghetto style is ghetto
 

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DIY Guru
96 Ranger-stock
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637 Posts
Discussion Starter #8
That is a bit excessive time wise, How long is the valve on the seat when it is running? Even at Idle speed.

If it holds for 5-10 seconds, you are good
 

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Asshole
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I did it the opposite way and filled the combustion chamber. The fluid ended up leaking out of the exhaust port.
 
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