Too long and the valves might not close.

 

How about valvetrain noise? Specifically, lifter noise. If the pushrods are too long, can I expect a noisier valvetrain (IE, lifters). How about if they're too short?

Thanks

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Pro Stock John:
<strong>Too long and the valves might not close.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">

 

What are the typical signs of too long or too short pushrods? I know how to check the lifter preload, but am unable to do so for a few days. <img border="0" alt="[Banging Head]" title="" src="graemlins/gr_banghead.gif" />

 

I was wandering the same thing. How would you determine this? If you change the cam do you need to change pushrods?

 

i know from experience that longer push rods will cause louder valvetrain noises.

if i remeber correctly the right pushrod length is the one that leaves the rocker tip on the center of the valve stem at max lift, some one please tell me if i'm wrong about this.

 

You look for the rocker tip to be centered on valve tip exactly 50% lift. Here is the hard part the lifter has to pumped up like actual running conditions to accurately check. Big buck motor not many will skimp on details! <img border="0" title="" alt="[Roll Eyes]" src="images/icons/rolleyes.gif" />

 

There was an article on this in the Engine Masters magazine, and I think Hot Rod also. It stated that a trick engine builders use is to mark the tip on the valve with a Sharpie (marker), bolt up the rockers & pushrods, turn the engine a few times, and take off the rocker & look for wear mark in the center of the valve tip. Very good info, you might want to try & locate the magazine. I'm sure you could use this method to determine proper pushrod length (ie: optimized valvetrain). Good luck.

 

If you have improper length pushrods, your valvetrain will sound like a diesel. If your pushrods are grously out of tolerance, you run the risk of hanging your valves (like PSJ said) which will destroy your exhaust valves, or you will float your valvetrain at abnormaly low RPM.

Here is a method to check if you have the proper length pushrods.

1) Ensure that the cylinder in focus is at TDC, with the lifters on the base circle of the cam.

2) Install one pushrod on top of the lifter. Install the associated rocker in the proper position, but do not tighten it down.

3) If you have skinny fingers, turn the pushrod, and slowly tighten down on the rocker. You will eventually reach a point in which you will not be able to turn the pushrod anymore. This is the point of zero lash. STOP TIGHTENING

4) Get your torque wrench out and set it to 22 ft/lbs

5) Okay, now there is some debate on this part.... Slowly tighten down on the rocker with your torque wrench to 22 ft/lbs. Count the number of turns made by the torque wrench that it took to get to 22 ft/lbs.

According to the crane technical folks (and me just your regular enthusiast with a kick-*** valvetrain that sound like a sewing machine), the number of turns that you should count is somewhere between 1/2 and 1 turn.

According to some engine builders, you should count up to 2 turns for a "quiet" valvetrain.

Either way, if you are in this ballpark you will have the "proper" length pushrod.

The above mentioned method of using machinist dye to determine that the rocker is landing at the exact center of the valve will work as well, but isn't as straight forward. The dye trick will also tell you if you have proper rocker geometry as well though.

Good Luck
<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />