[tquinn83]

Last summer I built a 357 sbc with a hydraulic flat tappet cam, hardened pushrods, and aluminum full roller rockers. I had problems with the no.2 intake rocker coming out of adjustment. After three times of readjusting, i took a closer look. i took the pushrod out and measured it. it was a full 1/4" shorter than the rest!it only has about 6000 miles and i followed the advised break in procedure and used zinc enhanced oil. What could cause this?

[cdminter59]

I don't know what brand the pushrods are but it sounds like the metal it's made from is worthless. I would replace all of them with a one piece heavy wall .080 x 5/16 chomemoly pushrods. Comp Cams, Trend, and Manton are some name brands to look for.

[snakebit68]

You can spend alot of time wondering what you may have done wrong and what might have caused this...DON'T! Replace the pushrod! This could've been a factory flaw that has nothing to do with your engine or your skills. Replace just that one and see if the problem repeats itself. If it doesn't...leave the new push rod in, or replace all of them with a namebrand set from comp cams or similar. If it does repeat itself...check the rocker arm for flaws. Swap rocker arms with another cylinder to see if it does it to that one. It could be a lifter that is pumped up and not compressing at all. If it doesn't collapse some it will hammer that pushrod. Just a couple of thoughts. Not really expensive to track down and fix...just a bit of time and trial.

[engineczar]

Was this a one piece pushrod or was it the type with a welded ball on the end?

[tresi]

1/4 inch? Is it bent? There is not a 1/4" of metal on the end of some pushrods even if you add both ends together. Even a good pushrod would hardly have that much metal to wear off. Check the cam lobe of the valve that needs constant adjustment. you might be loosing a lobe.

[MouseFink]

You probably pumped all the lifters full of oil before turning the engine over to set the lifter pre-load. One lifter happened to be sitting on the nose of a cam lobe and was holding the valve open as a piston reached at TDC and bent the push rod. The reason it did not happen to other push rods is because the offending lifter was more difficult to bleed down because it had more rust preventive left over from the manufacturing process. The clearance between the lifter's plunger and lifter wall is only .0002". Sometimes you can get away with filling the lifters with oil and sometimes you can't.

That is the only reason I can think of that would cause a push rod to get bent before the lifter pre-load was set and the engine was started.

[tresi]

Let me state myself better. I'm not doubting that the pushrod was shorter because I wasn't there to see it. If the pushrod wore that much it must have surely worn through the manfactured end or be bent. Having to readjust just 1 rocker is a very good sign that you are wearing the lobe off a cam or maybe in this case a pushrod. Did it pop a ball off the end. Detailed pics of the end of the pushrod would help. If an end did wear like that I would think that the cup in the rocker or the lifter would be damaged too.

[snakebit68]

It struck me as odd that you stated the push rod was 1/4 shorter then the rest ... indicating that it was intact and not worn at the balled ends...could you specify if there was visual wear or bend on the push rod. Otherwise it could simply be s shorter push rod installed by accident. If it were a bad lobe, lifter, or rocker arm...there should be evidence of damage to the push rod...not simply shorter then the rest.

[cobalt327]

Originally Posted by tquinn83

Last summer I built a 357 sbc with a hydraulic flat tappet cam, hardened pushrods, and aluminum full roller rockers. I had problems with the no.2 intake rocker coming out of adjustment. After three times of readjusting, i took a closer look. i took the pushrod out and measured it. it was a full 1/4" shorter than the rest!it only has about 6000 miles and i followed the advised break in procedure and used zinc enhanced oil. What could cause this?

If you measured it by removing it, you have a too-short p-rod mixed in w/the rest. If it was worn that much, one end would be a hollow tube. If it was bent so bad that it was 1/4" shorter than it should be, you would be able to see that from 10 feet away.

[snakebit68]

Thank you Cobalt327...I think you stated it far simpler then I managed too, but thats what I was trying to say.

[cobalt327]

Originally Posted by snakebit68

Thank you Cobalt327...I think you stated it far simpler then I managed too, but thats what I was trying to say.

You posted while I was still typing so I didn't see your post! lol But you're correct, I believe.

[snakebit68]

Might be a good sign that we're both intelligent....or both dopey as hell. LOL

[engineczar]

Originally Posted by engineczar

Was this a one piece pushrod or was it the type with a welded ball on the end?

My thought is that the ball popped off. I've seen the it happen on more than one occasion. Once you've seen it happen you'll never use one of that type agaIn.

If that's not what happened then either the rocker or lifter is toast as well.

[cobalt327]

If there is damage, the end popping off would make the most sense IMHO.

[tquinn83]

The pushrod is a summit piece with welded tips. It's straight a an arrow and am 100% sure it was the right length when it went in. It has obvious wear on the rocker end, as it is much flatter than it ought to be. The tip hasn't come out.