Tappet screw

[Aardvark]

Hi again
I need someone to help me get my head around a problem on my 72 crossover.
When we got it a couple of years ago, the first thing I did was give it a good service. One of the things I noticed when setting the valve clearances was that one of the tappet screws on No. 4 was wound right in. I removed it for a look and found that the nub on the end of the screw was missing or worn away, so that it was the screw section that was bearing onto the valve.
I changed the screw for a new one from Just Kampers. Now we move to the present day. I noticed that the engine was getting tappety again, so decided to set the clearances. I found all the clearances were good apart from that same screw. It was worn down again, just the same as before. I had no choice but to set the clearances as-is until I can get another new screw. I obviously did an oil change too.
Can anyone explain what the hell is going on? It's got me stumped.
Cheers
Aardvark

 

[atafonso]

Hi

There might be a blockage on the oil gallery for that rocker arm, so no oil is going to the tip. It`s quite common on older engines or in engines that used low quality oil or even on engines that don`t run a lot and don`t get to normal operating temperature very often, therefore creating carbon build up.

Could you please post a pic of the wear pattern on the screw?
The adjuster is supposed to sit slightly offset on the valve in order to rotate the valves as it pushes them down. If the adjuster is not in the right position, it will wear unevenly as well.

Abel

 

[Aardvark]

Thanks Abel.
When it stops raining, I'll take it out and photo. It sounds reasonable though. I'm presuming that if I took off the rocker shaft and thoroughly cleaned the oil ways, it should go a long way to solving the problem.
For oil, I use SAE 30 Golden Film. It gets changed every 2-3000 miles. But the van doesn't get too much use. The fact that it was like this when we got the van would suggest a historical problem. At least I know what to look for now.
Aardvark