rotating pushrods

[v8 dave]

Hi, are pushrods/lifters supposed to turn at the same speed when the motor is running at idle,when I watched mine some spin quite slowly and some spin faster is this normal,Thanks dave

[Real McCoy]

As long as they are turning I think you'll be fine. I have never heard that they had to turn at equal speeds, just had to turn. I run roller cams and now you got me wondering if my pushrods roate at all. I bet they don't.

[ratonabike]

oh they definitely turn... but never equally and not necessarily even in the same direction... some may hardly turn at all, but will rotate slowly at least. i'll try to find the link to a vid i once had, a closeup highspeed slomo video of the valvetrain of a performance pushrod motor while running under various rpm's. the vid was about showing valve float at high rpm, it was amazing to watch everything moving. the pushrods were rotating, the valve springs were turning every which way, it's amazing that the valvetrain ever stays together concerning the stresses they go under at high rpm, another reason never to go cheap and cut corners with valvetrain parts.

[ratonabike]

hmmm... i found the vid, maybe i'm wrong (so much for my feeble memory), as the video only shows the valve/valvespring/retainer/rocker in action... and given the 10,000 rpm title in the beginning, and the car, this is a non-pushrod motor... but i would suspect, especially watching this vid, that the pushrods in a pushrod engine is going through similar motion... there's nothing to keep a pushrod from turning, so i would be highly surprised to think a pushrod always stayed static, especially when you see how everything else is rotating.

here's the vid... amazing to watch...

http://www.youtube.com/watch?v=_REQ1PUM0rY

[ratonabike]

here's another vid of valvspring float, on a typical nascar pushrod motor, and u can see how the springs and retainers are bouncing around... i would be incredibly surprised to think the pushrods were static.

http://www.youtube.com/watch?v=i_NpzU4pGjc

[ratonabike]

ok this is the last one... i just can't get tired of watching these.... crazy!

http://www.youtube.com/watch?v=cfGg15WgSEU

[Real McCoy]

Lifters have to turn because they are ground that way and aren't flat on the bottom. They turn which makes the pushrod turn. All that sort of makes sense but a roller cam lifter is fixed and can't rotate. So what is going to make a pushrod turn?

[ratonabike]

hmm,, well if there's nothing to keep it from turning, wouldn't u think that it would just from the high rate of motion of the entire valvetrain, or simply just affected by harmonics? and there's nothing to keep the pushrod from turning as it sits on a film of oil between the lifter and the rocker... i'm gonna have to remember to mark them next time i have my valve covers off and see if the markings move

[v8 dave]

Thanks for the info guys,gives you a bit of piece of mind knowing that your cams not going flat!