Adjustable rocker ratio

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1970 La

1970 La

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I checked my rocker arm ratio on the old 273 ductile rocker arms and most of them are 1.46-1.44. This was at zero lash.

Any body seen these even close to 1.5?

Was also wondering how close the crane's were on ratio. Any body know?
 
Even with a perfect 1.5 ration rocker..the mopar la engine is going to lose lift at the valve due to the angle of the pushrods...
 
I have a .344 lobe lift x 1.5 would .516. I am getting .497 at the valve so considering the loss in push rod angle probably is not to bad. Just curious about the crane rocker. I am sure I would never miss the loss in lift.
 
70aarcuda said:
Even with a perfect 1.5 ration rocker..the mopar la engine is going to lose lift at the valve due to the angle of the pushrods...
Click to expand...

How much? I wonder that have anything to do with the ball/cup or ball/ball design.
Did the clay/puddy test to make sure I wouldn't hit the piston and I got max lift. Mind you he did use hyd roller that were soaked in oil prior.
 
has to with the geometry ....lifter bores are at 59 degrees...the valves are at 48 degrees...


take the cos of the difference 11 degree...that is your correction factor ...


and that does not take in account of any pushrod flex...
 
70aarcuda said:
has to with the geometry ....lifter bores are at 59 degrees...the valves are at 48 degrees...


take the cos of the difference 11 degree...that is your correction factor ...
Click to expand...

And I thought my high school trig was a waste of time, shoulda' paid more attention.
 
Never got past Algebra. LOL Mine weren't 1.5 either and the difference in angles can be tricky when you mill heads and grind valves and install new ones. I used the phrase "tolerance stacking" when I went through my 273. So many things were changed some adjustments had to be made with pushrod length and shimming the rocker shafts to get the angles closer to correct. tmm
 
Now, after the confusion...
How did you determine actual ratio of those 273 rockers?
Or do we have a correct number here?(after reading Tony's math in the other thread, I'm guessing those things were NOT taken into account).
Which brings us back to "What is the true ratio of 273 rocker arms?"
Not knocking what you came up with 1970La, just really curious myself, too, as I just picked a set up myself for my 318 that I want to run with a solid lifter cam.
(Also, a big thanks to Tony for the good math)
 
I checked the lobe lift off of the lobe. The lift at the valve when I degreed the cam. I set the dial indicator up inline with the valve sitting on the retainer. Turning the engine over till the cam was at max lift. This is were I came up short.
 
Using Tony's math I am loosing .009 at the valve and the rest in the ratio. So .497+.009=.506 that leaves .010 in the ratio. I just took .497 devided by the lobe lift of .344 = 1.4447. But was not thinking of the loss in the push rod angle and blaming all the loss on the ratio. Thanks Tony I will keep this in mind for future confussion lol!
 
I'll add the higher the lift of a given cam, or the taller the lifter (i.e. hydraulic rollers) the more lift you lose.
And - factory rocker ratios are never what they advertised. Stamped are not 1.5 either, and they lose more due to flex.
 
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