Hey guys, a couple of questions on the Miller rockers. I purchased a used set of Mid-Lift rockers from Scott at RHP and I want to clarify the setup on these to make sure I get my pushrod length correct and the setup correct. I would call Scott directly now but I'm not yet in a hurry and figured it might be useful information for others that are (or may) use these rockers.

I've never setup roller rockers at all so I'm learning here. I've read through the setup document from Miller on the setup and I just want to have someone that is more familiar with this system tell me that I'm understanding things correctly and going down the correct path.

For the sake of simplicity, I'll work from the specs of one intake valve. Per the cam document from Scott, intake lobe lift on this cam is .518. Rockers are 1.72. This will give me a .258 mid-lift point at the lobe and multiplying the rocker ratio will give me .891 net valve lift and .445 mid-lift at the valve. As I understand it, using a dial indicator on a solid lifter on this lobe (for the purposes of adjustment), I am to rotate the engine two full revolutions to confirm lobe lift but I'll use numbers above for this calculation. Using same dial indicator on the lifter, I rotate to the mid-lift point which would be .258. Then I move my dial indicator to the top of the valve spring retainer and zero it here. Insert my adjustable pushrod set to somewhere near stock length, install the rocker and crank the adjuster down until my dial indicator reads at the .445 valve mid-lift point. From here, all I do is check for a 90 degree right angle against the rocker face and the valve stem and adjust my pushrod longer or shorter until I get a 90 degree angle at the mid-lift point on the valve.

Is this all correct and making sense or have I missed something? If my calculated pushrod length is different between intake and exhaust, can I assume that slack will be taken up with the hydraulic lifter without negatively affecting geometry or if that happens to be the case should I get two different length pushrods?

I'd be posting this on the 460ford.com forum but my account is still not approved after registering a few weeks ago and I can't get an answer from the admins.

Anyway, any input will be appreciated.

 

The way I check push rod length is get or make a adjustable push rod. Set it to the stock length for now. If you have or can borrow a big set of dial calipers it will make measuring things easier. Put the cam lobe on it's base circle. Put a set of light weight checking springs on the valves being checked. Put the cylinder head on, make sure to put shims under the head the thickness of the compressed head gasket. Put some sort of compound on the valve tip that will leave a impression from the rocker tip. Put the rocker on and adjust the push rod or rocker depending if you have adjustables so there is no lash. Turn the crank being very careful not to compress the lifter plunger. Remove the rocker and note the pattern. It should be centered. If it isn't centered readjust the push rod and repeat. It may take a few times to get the pattern centered right. After you get it right add the preload to the push rod length you came up with IMO I always use .020. If you are running a solid cam subtract the figure. It is very important that the machinist that did the valve job set all the stem heights equal, otherwise you will need different length pushrods all over the place. If it isn't too bad you can get away with shimming the rocker stands if you don't have adjustables.

 

Mark,
I know this is an ancient thread, but was led here for a question on rocker geometry, and just wanted to let you know that checking springs and making the wear pattern sit in the middle of the valve is a waste of time, and not accurate. Precise geometry is easily set by measuring the trunnion CL to be below the roller pin CL by exactly HALF of NET valve lift. The trick is measuring at a perfect right angle to the valve, and the best way to do that is with the top of the valve spring retainer. It's all laid out in: Jim Miller

The way you describe is what most people do, and will lead to many false conclusions. The DOWN SIDE to all this, if you don't care about how much CAM you waste, is degrees of cam motion throughout the valve lift cycle. It is NOT limited to solely "full lift" losses. Velocity is lost, duration (at all lift points) and valve lift all suffer. How much? Try 4, 6, 9, 12 degrees and more. Just for missing this critical dimension by .020" or .030". Valve guide wear, increased spring surge, and reduced RPMS are also biproducts of this lack of accuracy.