Chromoly Pushrod Failure, Not in my motor, but a friends Options

['73-914kid]

Okay, so here's the scenario. I have a friend at school with a type4 powered bug. It's a built 2056 with 1.7L rockers, Manton Chromoly pushrods, etc, etc. Your typical proper 2056 build. Lately he had been having issues with getting a certain valve to stabilize on adjustment. Every 400-500 miles the lash would get a little loud. It was cured by about an 1/8 turn on average on the valve adjuster screw.

A couple of days ago, we tore into the valvetrain to try and diagnose what was causing the loosening valve. he had run a paint mark on the adjuster for about 500 miles, and had verified that the swivel foot was indeed staying locked in place. That narrowed down the options to possible failures of:
-Dropping valve-seat
-Lifter face failure (Cam lobe had to be fine given the opposite valve stabilized on adjustment)
-Pushrod cup in lifter
-Pushrod cup in rocker arm
-Pushrod failure.

After 5 minutes of tear-down the problem was obvious. We unbolted and removed the rocker shaft, and then got to removing the pushrods. As I attempted to remove the pushrod from the engine, I pulled the tip out of the pushrod. Well there's your problem.... (IMG:style_emoticons/default/huh.gif)

The pushrod tip had become completely loose in the chromoly body, and was wearing it's way down into the body of the pushrod. I wish I would have taken pictures of it. When we compared the measurements to his table with the cut lengths from the initial build, it had shortened itself about a 1/8inch slowly, in a period of 2000 miles. I'm just glad we caught it before something catastrophic occurred. I managed to find a VW shop local that had a single chromoly pushrod uncut laying around, and we cut it to the correct length, and slid it back in place. Problem solved.


So, has anyone else every experienced a failure like this? Could it have been an assembly error from pressing in the tip cocked to one side?

So the moral of the story is, pay attention and listen to your engine before it decides to blow up on you! (IMG:style_emoticons/default/ar15.gif)

[DBCooper]

Could it have been an assembly error from pressing in the tip cocked to one side?

Seems unlikely, but yes, that's possible.

[VaccaRabite]

Maybe a miscut rod?
Did he by any chance over ream the inside edge after cutting, not giving the cap a firm ledge to seat on?

Once it got past the lip, I can see how it would be driven in. Getting past the lip is the real trick. Do you have any pictures?

['73-914kid]

That was part of the conclusion that we had come to. He can't remember if he was over-zealous with the deburring tool after it go cut, however it definetly would make sense..

I didn't take any pictures. I will thursday night when I get home though

[Jake Raby]

Manton had an entire batch of soft pushrods some time ago.. We caught these thorough our development and never sold any.. Others never knew about it and continued selling them. That could have been the problem.