Harland Sharp Roller Rocker Geometry/Pushrod Length

[390rpm]

Can someone walk me through setting up these rockers. I have an adjustable pushrod length checker. The heads have been decked and the pedestal surface was milled to match, or something like that. My dad had them milled, so I'm not totally sure.  Should I set the the thread length of the rocker, adjust the length checker to where it's not compressing the lifter, set the preload, check the valve tip pattern, and go from there? It's my first time setting an adjustable setup on an FE. I'll post some pictures of any progress. Thanks.

[blykins]

My angle of attack is to get the geometry right first, before measuring for pushrod length or worrying about where the adjuster is. 

The geometry on a shaft mounted rocker is set by moving the stands up (shimming) or down (milling).  You move the stands up or down to establish the correct pattern and geometry on the valve stem.   You're aiming for a narrow pattern near the center of the valve stem.  I would consider a narrow pattern to be .040-.060" wide.  If the pattern is wide and toward the intake side of the stem, then the stands need to be raised.  If it's wide and toward the header side of the stem, then the stands will need to be milled.   Most of the time, I'm shimming up Harland Sharp rockers.

Once that is done, then you set the adjuster so that it's as tight up to the rocker body as the pushrod cup and oil hole will let you get.   If the adjuster is long then you end up with the adjuster being a moment arm, and more importantly, you get lots of "wiggle" movement of the pushrod cup during the valve open/close period.  That wiggle translates to less lift at the valve.  If the adjuster is too short, then you'll get the pushrod cup up into the lifter body, where you will have contact or failure. 

After all that is established, I measure for pushrod length and then add .050-.060" for hydraulic lifter preload. 

If it's a ball end adjuster on the rocker arm, then you will need a ball/cup style pushrod.   When you measure, put a ball bearing or similar into the cup, then use calipers to measure the OAL, then subtract the diameter of the ball bearing.  This is called the "bottom of cup" measurement and it's a standard for measuring ball/cup pushrods.

[390rpm]

Thanks Brent! I watched your video on the 496 build and you mentioned your technique. My question is-- To find my pattern to check the geometry, do I mark the valve tip and use the technique I mentioned? I guess I'm asking what method do I used to actuate the rocker and valve to get the pattern if I don't have the correct pushrod yet?

[blykins]

I have a box of individual pushrods that I can slap in there and try.  I understand that most guys don’t. 

You can also  use a checking spring and the head doesn’t even need to be on the engine.  Since pushrod length doesn’t affect shaft rocker patterns, you can literally get a picture by using a checking spring, marking the valve tip, and actuating the rocker by hand.

Some guys like to use the midlift theory for geometry and you can still do that, with a dial indicator on the retainer to check lift and position.

If it’s a fairly low pressure valve spring, some high quality length checkers will even be strong enough to actuate the valve.

[390rpm]

I got yah. I was thinking about doing it by hand (probably will) or using a solid lifter and the pushrod checker to roll it over and get a pattern. I'll do that, get the length, and use a dial indicator on the rocker to set preload. Thanks!

[blykins]

It will be a full turn of preload but you don’t have to mess with preload now, you can add it to the length of your pushrod at zero lash/preload.

I’d just get the adjuster in the spot you want, then add preload to the pushrod length.  That way your adjuster position won’t change as much.

[390rpm]

Hahaha, you're right. I suppose I could. Thanks!

[fryedaddy]

when you get done and adjust preload,hs suggests 0-2 threads showing on the bottom side of the rocker,i have 1 showing on the bottom of mine.

[390rpm]

Yeah, I'm going to run them up with as few showing as possible.

[390rpm]

Possibly a dumb question, but I don't think it matters if my checking spring is the same as my installed height? Right? As long as it keeps the keepers and retainer holding the valve it shouldn't matter.

[blykins]

Possibly a dumb question, but I don't think it matters if my checking spring is the same as my installed height? Right? As long as it keeps the keepers and retainer holding the valve it shouldn't matter.

The spring install height doesn’t affect how high the valve stem tip is.

[390rpm]

The spring I had was a little short. I went ahead and got another one. Haha, I also like to assume that I'm wrong or ignorant to something obvious. Thanks for all the help it's much appreciated.

[Skeeter65]

390rpm, I will be going through the same process with HS rockers eventually, so any details on the method you used would be helpful.

[390rpm]

I'm back in the city for a couple of days, but I'll get back to the shop tomorrow or the Wednesday. I'll try to post up some pics and detail any issues I've had. The most difficult thing thus far was pulling the pedestals off. Other than that it hasn't been too bad.

[390rpm]

I'm back at the shop. I took my new pushrod length checker out of the tool box and measured the ball and cup. The Cup end is 5/16. My Rocker arms are 3/8. Darn.