Figuring out pushrod length

Gene Fiore

Famous Member
The ball and cup pushrods I have been running are now too short when doing mockups with the aluminum head...and actually they were already on the short side. In lieu of using an adjustable pushrod I want a way to determine how much longer pushrods I need and then order them. If I depress the adjuster end of the rocker down so it seats in the pushrod cup can I then just measure the clearance between the valve stem and the underside of the rocker where it would contact the valve stem to determine how much longer of a pushrod I need? :unsure:
 
Gene Fiore":nk6yhovh said:
The ball and cup pushrods I have been running are now too short when doing mockups with the aluminum head...and actually they were already on the short side. In lieu of using an adjustable pushrod I want a way to determine how much longer pushrods I need and then order them. If I depress the adjuster end of the rocker down so it seats in the pushrod cup can I then just measure the clearance between the valve stem and the underside of the rocker where it would contact the valve stem to determine how much longer of a pushrod I need? :unsure:
Here's what I wuz thinkin & here's what a pro (CNC-D) provided frm CompCam:

Another hint involves cup end pushrods. Measuring them for length is especially difficult, no matter which technique above you choose to use. The size and shape of the cup end varies greatly from manufacturer to manufacturer, so measuring from the ball end to the cup end over the cup surface is a dangerous practice. The best strategy is to drop a 5/16” diameter steel ball into the cup end, and do all your measuring over this ball, subtracting the 5/16” diameter (.3125”) to figure the length.

I bet U come up w/something even beddah den dis !!!
 
drag-200stang":j4aapd8f said:
Gene, What rocker do you have exactly?
One of the classic inlines 1.6 ratio adjustable rocker assemblies...which required an aftermarket set of pushrods with a larger cup then oem pushrods.
 
Ok then you have fixed shaft rockers , this link should help...Pushrod length does not effect rocker to valve geometry, only moving the shaft!
http://www.eatonbalancing.com/2007/12/1 ... -geometry/
If you are happy with the as designed geometry, Then and the adjuster is in a good spot, not to far up or down..Then you could measure with a dial indicator the slop at the push rod / adjuster location, Make sure that you are on the base circle and rod is seated in the lifter..This is assuming that the difference is not huge or the arc will throw off the measuremen..See if that matches your plan if you divide by 1.6..You will figure something out.
Maybe Pmuller can chime in, he posted in another thread about this and can also help the understanding.
 
drag-200stang":yntgkw17 said:
Ok then you have fixed shaft rockers , this link should help...Pushrod length does not effect rocker to valve geometry, only moving the shaft!
http://www.eatonbalancing.com/2007/12/1 ... -geometry/
If you are happy with the as designed geometry, Then and the adjuster is in a good spot, not to far up or down..Then you could measure with a dial indicator the slop at the push rod / adjuster location, Make sure that you are on the base circle and rod is seated in the lifter..This is assuming that the difference is not huge or the arc will throw off the measuremen..See if that matches your plan if you divide by 1.6..You will figure something out.
Maybe Pmuller can chime in, he posted in another thread about this and can also help the understanding.
Ok cool...problem is I can't get my dial indicator inside the cup to measure the distance from the bottom inside of the cup to the underside of the adjuster. I can measure the opposing distance between the valve stem and the underside of the rocker. Would that typically be the same measurement?
 
Gene Fiore":3ay4yyk2 said:
drag-200stang":3ay4yyk2 said:
Ok then you have fixed shaft rockers , this link should help...Pushrod length does not effect rocker to valve geometry, only moving the shaft!
http://www.eatonbalancing.com/2007/12/1 ... -geometry/
If you are happy with the as designed geometry, Then and the adjuster is in a good spot, not to far up or down..Then you could measure with a dial indicator the slop at the push rod / adjuster location, Make sure that you are on the base circle and rod is seated in the lifter..This is assuming that the difference is not huge or the arc will throw off the measurement..See if that matches your plan if you divide by 1.6..You will figure something out.
Maybe Pmuller can chime in, he posted in another thread about this and can also help the understanding.
Ok cool...problem is I can't get my dial indicator inside the cup to measure the distance from the bottom inside of the cup to the underside of the adjuster. I can measure the opposing distance between the valve stem and the underside of the rocker. Would that typically be the same measurement?
No you will have divide the measurement at the valve by 1.6 to get what you need at the pushrod...Check the play at both ends and see if that maths out
I was thinking put the indicator plunger on top of the rocker lined up with the center point of the adjuster ball along the top side and measure the play....... or maybe small hose clamp something to the pushrod and use the indicator to measure the play keeping the rod lined up, up and then down , lined up the best you can ...Add the difference to your pushrod...
 
Thanks for the responses drag-200...I've never even used a dial indicator before :( and I just bought one today. A picture of what you are describing would be worth a thousand words of the technique you are describing...even if it is on something unrelated. ;)
 
Gene
google... '' pics of dial indicator on rocker arms '' and also click more images.. this should give you some rough ideas , have to play with it.
Hope you got the magnetic base with it, best 24 dollars I spent, indispensable. (y)
 
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