Wipe pattern question

[eddieeats]

Hey everyone I have a 77 280 and am rebuilding the stock engine. I’ve upgraded the camshaft to a stage one with a lift of 460 and duration of 260. My N47 head has been to the machine shop for cleaning and reseating of the valves, he only shaved .010 off to flatten the bottom. The rocker arms, springs, retainers & lash pads are all new. My concern is the wipe pattern that I’m seeing, I have two different size lash pads .170 & .150, Motorsport doe’s not have the .160 and I can’t seem to find them anywhere. with the .170, after setting the valve lash, I’m seeing a wipe pattern centered on the lash pad (follower guide) but comes very close to falling off the valve side of the rocker arm, less than 1.5mm. I installed the .150 lash pads and now the wipe on the rocker has centered but the wipe on the lash pad has moved off center toward the pivot. I’ve checked all 12 and can’t seem to get them both centered at the same time.

 

I’ve been searching and reading about this but can’t find anything about the importance of the wipe on the lash pad, here’s a photo of the wipe on all 12.

 

My question is will the wipe on the lash pads be ok to use or is there another option I’m missing?

 

Thanks

[duragg]

Wish I knew exactly what to tell you but I am in your same position (1 month behind...).

 

In one of my 3 heads I scavenged parts I found an MSA Spring Kit, Cam and Pads.

The pads were 160s, 170s and a 190.

 

It would be a simple thing to take 10 thou off a 170 with the right equipment.

[madkaw]

Your wipe pattern doesn't look too bad to me, but I'm not a cam expert by a long shot. Here is a snipet from a great article by Racer Brown cams regarding this contact area.

 

 

One highly important item may contribute some conflict of interest at this point: The actual area, and location of the area, of the rocker arm pad contacted by the cam lobe, hereafter referred to as "rocker pad contact patch." Some cam lobe profiles do not allow much if any latitude here. With these engines it is AB-SO-LUTE-LY ESSENTIAL that the cam lobe does NOT extend beyond either end of the rocker pad. For the most part, this occurs on strictly race engines, but if the cam lobe profile is sufficiently desirable, the rocker arm position must be adjusted at the pivot end so that the cam lobe does not override either end of the rocker pad. If, by mischance, miscalculation, or simply the wrong cam lobe profile, an override condition exists at either or both ends of the rocker pad, it spells instant death to the cam lobes and the rocker pads.

If the cam lobe is a tight squeeze on the rocker pad, then the first order of business is to make certain that the rocker pad contact patch is as correct as it can be, and rocker arm geometry must be forced to a secondary position.

Ideally, the rocker pad contact patch should be centred on the rocker pad. Assume that the opening flank of the cam lobe comes within 1/32-inch of one end of the pad and that the closing flank of the cam lobe comes within 3/32-inch of the other end of the pad. This is wrong. The rocker arm position must be raised at the pivot end of the rocker so that the contact patch is equalised at 1/16-inch from each end of the rocker pad. There is a good visual method of checking and measuring the rocker arm contact patch, and there is also a way to "cheat" a bit to gain a higher effective rocker arm ratio in some cases…but that comes later.

[2eighTZ4me]

That wipe pattern looks fine. You're more concerned about the cam to rocker contact than you are rocker to lash pad. There's a lot more friction going on b/t the cam and rocker than the latter. The "cheating" referred to in the RB article is getting your wipe pattern a little closer to the adjuster side of the rocker (away from the lash pad) - causing just a wee bit more lift. This is usually a .010" increment up in lash pads. So, if you had to err, err on the side of the adjuster instead of closer to the lash pad.