Worn Valve Guide

FordTudor1931

FordTudor1931

Member
My 31 Tudor had a 20 psi lower compression on in cylinder #3 combined with a ticking noise in that area. I started the work by removing the valve cover to check the valves, and as it turns out adjust the valves (didn't know adjustable tappets had been installed). The exhaust valve for #3 did not close at all which of course could explain the compression problem.

However, nothing changed after the adjustment. Still low compression and the noise still there. Time to pull the head and check things out. Everything looked OK after pulling the head, but I still decided to remove the valve springs, guides and valves to see if anything could be found. As it turns out, seven of the eight valves and guides were in great condition, while the exhaust valve for #3 cylinder was completely worn down (see pictures!). It looks like total material failure on this one guide.

Happy to have found the problem but confused over how it could have happened.


Guide 1.jpg
Guide 2.jpg
Guide 3.jpg
Guide 4.jpg
Guide 5.jpg
 
I don't know if the valve guides are hardened or not. My guess would be that the something abrasive got in there and scoured the guide.
 
I imagine you did not do this. I tapped oil for a filter off the fitting on the side of block. This did not allow no 3 exhaust to get enough oil up through the pump shaft. You could wiggle the valve a lot when open. The loose valve also took out the hardened seat.

You might check your seat if the valve had play.

John
 
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Also the part on the dustributor drive has grooves that spew oil on the valve stems. You might want to check that there is no carbon in these grooves.

It looks to me that your valve failed from lack of oil somehow.

John
 
Dick Steinkamp said:
The guide is certainly bad, but I can't see how a worn valve guide would cause a compression loss.
Click to expand...

The valve closes off center, hits one side of the seat, and then snaps into the seat, centering itself. In the process, it wears itself and the seat out of round, thus causing compression loss.
 
Here is a picture of the valve. Out of curiosity I measured the stem of the eight valves and the variance was .002. The valve in the bad guide was no different than the other ones. The valve seat looks perfect and there does not seem to be any damage at all.

With the valve being able to move sideways enough to leave an open space at the edge even when "closed" would leak out compression. Sounds like a reasonable explanation, but what do I know?
 

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Was the exhaust valve that was stuck open the same one that had a bad guide? A bent guide could eat a guide but bad guide won't bend a valve. How are you checking valves for straightness? Any valve could get bent trying to get off a stubborn head.
 
Yes, the valve left open is the same with the bad guide.

I checked the valve stem by putting it through the other valve guides to see how it moved. Since the guides are good and the movement is smooth, the valve stem has to be straight.
 
31, I think you might be thinking with your wallet. Every one has done that. Get some help. Was the open exhaust valve open because the cam lobe was up. What happened when you turned the crank? Did it close on its own? Then you didn't have a stuck valve. You took it all apart before you had really found the issues. .002" is enough wear to replace valves but at worst would cause oil burning and erratic misfire off idle because of the shot guide.
 
The valve was left open because the lock nut on the tappet was not secured. The tappet screw had unscrewed (or never been correctly adjusted) not allowing the valve to seat even when the tappet was on the heal of the cam lobe.
 
Now I'm confused (it happens easily :o)

You said in post #1...


"The exhaust valve for #3 did not close at all which of course could explain the compression problem.

However, nothing changed after the adjustment. Still low compression and the noise still there."


...which led me to believe that adjusting the valves did not solve the loss of compression problem.

Then in your latest post you said...


"The valve was left open because the lock nut on the tappet was not secured. The tappet screw had unscrewed (or never been correctly adjusted) not allowing the valve to seat even when the tappet was on the heal of the cam lobe."


...which (I think) says that with the valves adjusted, the low compression problem would have gone away.


Did you just not find the mis adjusted valve on #3 when you adjusted the valves or am I missing something?
 
I did adjust all valves and they all seemed to move correctly (from what I could see in the valve chamber). The surprise was that this did not fix the compression problem on cylinder #3.

That is when I decided to pull the head to investigate further and that is when I discovered the screwed up valve guide.

The assumptions from the beginning were 1. sticky valve 2. incorrect valve adjustment 3. something else (piston ring??)
 
I'm still confused.

Watching the valves move up and down in the valve chamber is not a good indicator that they are adjusted correctly. Are you sure each valve was adjusted with the lifter on the heal of the cam?

When did you discover that the nut on the tappet was not secured? While you were adjusting the valves or after you disassembled things?

Have you tried to duplicate the valve "stuck open" condition with the head off? Does adjusting the valve correctly allow it to seat, or does the bad valve guide cause it to stay open?
 
Watching the valve movement in the chamber jut proved that the valves weren't sticking. The adjustment was done the usual way (rule of 9, .013 and .015) and that is when I discovered the out of whack tappet screw and lock nut.

The goal was to fix the low compression without having to remove the head. However, that was not to be.

I can't make the valve hang, but since there is sideways play, because of the worn valve guide, it doesn't seem to seat correctly on every closing. This of course just when cranking the engine. It might look and behave quite differently when running. That I will never know.
 
Who, 31 You opened a whole new world with the details recently provided. And look what happened.!
 
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