Gsoleski

I found the pushrod length I believe I need. Picked one up from the local part store just to check and I'm having trouble with some of the valves having wear patterns that aren't centered on the valve tip. This is with sharpie turning the engine over letting the valve open once. I didn't have time to mess around with guideplates but do they just need to be moved over a tad? The first one looked okay but the next ones favor one side. BTW this is with 1.6 RR, manley guideplates, arp studs, hot cam, blah blah

This is the first valve I tested (exhaust)

intake on the same cylinder

Tested the intake on the next cylinder, same thing

sofakingdom

iTrader: (1)

Doesn't matter where on the valve the pattern falls (within reason, which those are); what's important is, that you find where it is as narrow as possible.

The rocker tip moves through an arc, not a straight up-and-down line. It is closest to the intake side of the valve stem at rest, slides across the stem toward the exhaust side and goes the farthest that way at roughly half-lift, then as it continues toward max lift, slides back toward the intake side again. The narrowest pattern means that the arc is exactly split in half by the mid-lift point; the part of the arc that occurs before the tip reaches its farthest extent of travel toward the exhaust, is exactly equal to the part of the arc that occurs afterwards.

This results in the least amount of force from the rocker trying to slide sideways across the stem, which is what wears guides. The wider the pattern, the more sliding; and therefore, the more wear.

Do the following "thought experiment": put a pencil on your desk, and push on the eraser with the tip of another pencil. First push on it exactly in line with it, with the tip of the other pencil exactly centered on the eraser. How does the pencil move? Does it try to move to the side, or does it try to slide straight along its length? Now move the tip of the other pencil out to the edge of the eraser and repeat. Did the pencil's motion change much? Now put the point back in the center of the eraser and push at a slight angle to one side. What happened this time?

That 3rd scenario is what you want to avoid. Requiring the guides to resist substantial sideways force like the pencil experienced, is what wears them out.

Ideally you want the push rods just slightly shorter than "perfectly centered"; that way, when there's greater load on it at full lift than the lighter load nearer zero lift, the rocker is moving across the stem less. You want to "bias" it slightly toward that direction, emphasis on "slightly". Like, find the optimum length by way of the narrowest pattern, and pick the next size shorter. Since they come in .050" increments that's pretty easy. And since when a cam is made "bigger" the lobes are actually SMALLER at zero lift, the push rods will still usually end up being longer than stock, with most modern aftermarket cams.

AlkyIROC

For best results, you want the narrowest pattern possible even if it means it's not directly in the center.

Gsoleski

Sofa thanks for taking the time to write that, appreciate it. Ill mess with this again today and see if I can get it a little more narrow