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Spinning pushrods


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Just refitted my cylinder head after my torque wrench issue. No water leaks so far!.

Anyhow was running the engine with the rocker cover removed and noticed that the pushrods spin when the engine is running. Guessing this is meant to happen as I can imagine that is good for wear on the rockers..

Will deposit a video when I get around to putting it on Youtube...

Cheers

Tim

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Always keen to learn: Should they always be spinning, in other words: is non spinning definitely an issue?

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Not all of mine spin.. Have put the video on youtube

https://m.youtube.com/watch?v=JxPYJbkx6qE

Cheers

Tim

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I don't know that it is for sure a problem if the pushrod isn't rotating. It is not directly connected to anything so it is just the drag from the oil that would make it rotate with the lifter. If the lifter isn't rotating the cam will just dig a groove in it over time and I assume eventual lifter failure.

 

Stan (retired IT guy so I could also just be full of it)

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I suspect the pushrod rotation is more driven by rocker geometry. Interesting though..

Cheers

Tim

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I'll give you a clue, in similar circumstances piston rings rotate, if they don't rotate they wear...rapidly, it's what you find in engines when the piston "lands" (the piston material between the piston rings) have collapsed and nip the rings stopping their rotation.

 

Parts in "interference " fit with surrounding surfaces (piston rings, cylinder bores, cam followers, cam lobes, valve stems, rocker tips) if one of the rotating components in the partnership seizes it causes advanced wear in the parts. There is nothing securing these items in one position, of course they turn when exposed to forces, it equalises out the wear.

 

Tim, if we could show you an internal video of your engine when it's running at 3500 revs or varying the revs between on and off throttle I'm pretty sure you would see the components spinning, if they don't there would be wear.

 

Mick Richards

Edited by Motorsport Mickey
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Not just push rods and piston rings. Valves and valve springs spin too.

 

 

The video is correct - the conclusions in the captions are not.

Valve bounce can be cured by stiffer valve springs, but at the risk of accelerated camshaft/valve train wear. Better is double valve springs, that elevate the natural harmonic frequency of the valve/spring system much higher than the input frequency - as Triumph did.

 

John

Edited by john.r.davies
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