Uneven pushrod length ?

[1950split]

Hi,

I need the general opinion. My engine, 2276 with Brothers Mid-D heads, .130" lash caps and CB 1.4 rockers is nearly finished. Rocker geometry is finished and I have a good wipe pattern all around.

I'm however still left with ordering the pushrods and have them cut to length.

It is usually said that rocker adjusters should be turned out about 1 1/2 turns from touching the underside of the rocker. Well on my engine, for a pushrod length of 10.8" I can turn some out 2 1/4" turns and other 3/4" of a turn. I think that even with 3/4" the oil channel in the adjuster is inline with the rocker oiling hole. But what shall I do ? Cut all pushrods to same length or have different length ?

My valve stems with lashcaps all have the same height, therefore I assume that the difference comes from the lifters or the rockers.

Thanks for your help,

Phil

[yamaducci]

Assuming you are using the adjustable pushrod set to 10.8" and you just moved it from one rocker to the next; there are many variables that could effect adjustment. The fact that you have a minimum of threads; meaning the cup is very close to the rocker indicates the pushrod length is as long as possible. The longer the pushrod and the shorter the adjusting screw; the less fulcrum effect you have on lift. What all that means is the pushrod travels more linear and less up and down travel in the tube. The reason it's advantagious to be more linear is because you get a more accurate/consistent lift on each rocker due to less fulcrom lift. Once you get beyond 2-3 turns out you will begin to see drastic changes on lift due to the fulcrom effect compared to 1-2 threads out. 1-2 threads out can also handle more RPM and be more reliable than say 5,6,7,8 turns out.
I think you will be fine unless you really want to custom order lengths to compensate. I think you would need to identify a root cause and deem it uncorrectable before ordering unequal lengths.Assembly lube, rocker torque and friction play a part in why they are not as settled in as they will be after break-in. Each turn is only a few thousanths and negligable on valve geometry up to about 3 turns. Those lash caps are pretty big. Care to post a pic of them at zero lift to show the contact point?
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[Hustlers67]

I have the rockers with the adjuster at the pushrod (not the valve). They are 1.25:1.

I'm setting it up, pretty happy with the swipe and geometry in general. Just a question on the setting of the adjuster. I am using an adjustable pushrod, and it is wound in as short as it will go. I then have adjusted my rocker to zero lash, and that works out to be one turn out. Is this too little? I know the aim is one and a half to two turns out. Can I get away with just one turn out (from touching the underside of the rocker as described in the OP)

Any views?

[Dr OnHolliday]

I dont understand the point that was being offered about "fulcrum" issues.
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[mark tucker]

check stem hights,check lash cap thickness(all of them). if there all the same then rework the rocker's.but befor make sure the pushrods are fully seated in the lifter cups. I set mine up @ 1/2 turn out from the rocker max. and be sure to add a flat to the end of pushrods if there isant already one.

[Hustlers67]

Thanks Mark, so you go a bit further than others to set them at 1/2 turn out.
Can you explain the "flat" on the end of the pushrod - is this only at the rocker end? Or both ends? What's the purpose?

[mark tucker]

both ends.about 2~2.5mm dia at the hole. the pushrod should never carry a load there like it can if it dosent have a flat. do it on boith ends. and clean them out good.I use a belt sander to do all mine. many times the ball isant the right size or shape or both and it trys to sheer off the material in the cup from that sharp edge of the hole,a falt removes this ussue and lets the load be concentrated where it should be. I also rework the cup where the oil,hole is in it so it isant sharp at the edge of the oil gally hole,and then a nice raidi aroun the od of the cup where many are kinda rough or have a sharp edge.also check to be sure the threads are good neer the oil hole and no flash hanging in there. add a 1mm wide slot to the rocker threads one or 2 threads up or down if needed to line up the oil hole/slot in the rocker and adjuster when in running possion. I also do more mods to the rocker in the bush aera to put the oil where it is needed, not in the aera where it isant.