valves/head

[skids]

I just reconditioned a head and valves and reinstalled it. I checked shim clearances. All are fairly close except for the shocking distance at No. 4 exhaust. That clearance is huge. Oh crap, I thought, a stuck valve. This is not the case. I checked compression and all 4 cylinders are good. I put compressed air into the plug hole and it does not leak with the cams for closed-valve posiition. What could be causing this problem? It doesn't look like the bucket is rising as far as the others. Do you think maybe the button in the bucket below shim may have fallen off(!?) Any ideas are welcome.

[skids]

Re: valves/head

I just checked the bucket for movement with the cams still installed. With the magnet, the bucket rises freely and rotates freely in its place. I think the hardened button under the bucket must be gone. I guess I have to pull the cam, bull the bucket, and take a good look...

Originally posted by skids
What could be causing this problem? It doesn't look like the bucket is rising as far as the others. Do you think maybe the button in the bucket below shim may have fallen off(!?) Any ideas are welcome.

[skids]

Re: Re: valves/head

I just pulled the cam and the bucket. I compared the bucket with a spare from another head. They are identical. The button is there. I compared the keeper disks in the head with the lifter buckets removed (valves and springs still installed) with the other head. It appears that the keeper disk in the troubled head is not coming up as far as in the spare head. I wonder if the valve in the troubled head is identical to stock??? Or, maybe if the valve seat was replaced and thicker than stock??? Any ideas?

Originally posted by skids
I just checked the bucket for movement with the cams still installed. With the magnet, the bucket rises freely and rotates freely in its place. I think the hardened button under the bucket must be gone. I guess I have to pull the cam, bull the bucket, and take a good look...

[grifff]

valve

you sent all that info quick. I dont know much, but could a diff shim work better for you on #4?

[TopCatGr58]

Hey there Skids,

Sounds like you might have a shorter than OEM length valve. The bucket rides on top of the valve/keeper, and so if the bucket is lower, but you still have full compression, then the valve is seating. Only if the valve seat were coming out of the head, but you inspected it and did a valve lapping so I'm sure you would have noticed whether the seat was protruding into the combustion chamber!

If the keeper button is hanging up on the keepers, it might not rise fully up onto the valve shaft, that might lower the bucket!? That's about all I can think of! Good hunting!
T.C.

[skids]

I think you are right-on the money, TC. I resorted in taking the head off to examine the valve. It was a non-OEM valve. I pulled it and compared it to an OEM valve and the distance from the keeper slot to the seat surface was significantly shorter. I reconditioned a different exhaust valve and am almost to the point where I can remeasure the shim clearance with the cam. What a pain! I suppose I should have measured the shim clearances on that ebay head prior to the reconditioning the head, but I new I would be channging shims after lapping, and I did do a liquid leak test to check for bent valves... My mistake!

Grifff, They do not make shims that big. I couldn't even get an accurate measurement with several feeler gages put together.

Originally posted by TopCatGr58
Hey there Skids,

Sounds like you might have a shorter than OEM length valve. The bucket rides on top of the valve/keeper, and so if the bucket is lower, but you still have full compression, then the valve is seating. Only if the valve seat were coming out of the head, but you inspected it and did a valve lapping so I'm sure you would have noticed whether the seat was protruding into the combustion chamber!

If the keeper button is hanging up on the keepers, it might not rise fully up onto the valve shaft, that might lower the bucket!? That's about all I can think of! Good hunting!
T.C.

[skids]

TC, and Grifff, thanks for the input. It did turn out to be the incorrect length valve. Now, after replacing the valve, the clearance for the shim is very reasonable!

Originally posted by skids
I think you are right-on the money, TC. I.

[TopCatGr58]

Hey there Skids,

Glad you were able to find a simple explanation for it! I'm no GURU, but as we all have found here, some times it helps to have a different angle/viewpoint to look things over! Ride on!
T.C.