Rhoades Lifters

[MadBill]

... My lifter plunger movement is .040 for a 1/2 turn on an ARP 7/16-20 with a 1.6 scorpion rocker. The actual screw movement on the stud is probably .025. The distances of rockers from center to roller and center to pushrod cups are different from brand to brand. The ratios may be 1.6 but makeups are all different.

You bring up an important point Cobra, and your numbers are bang on, but rocker construction details don't affect results, it's all down to the ratio. For simplicity, assume the rocker's pushrod seat to pivot/fulcrum measurement is 1.0" and the fulcrum to valve stem contact point length is 1.50" for a total length of 2.50". In normal operation the rocker acts as a 'first class lever', therefore the ratio is 1.50/1.00 or 1.5:1, so 0.025" plunger pump up would translate to holding the valve 0.0375" off the seat.
When the adjuster nut provides the motion however, the rocker becomes a 'third class lever' with the valve stem as the fulcrum and so the ratio of plunger to adjuster motion is 2.5/1.5 or 1.67:1, thus 0.025" adjuster movement equals 0.025" x 1.67 = 0.042" at the pushrod.
https://en.wikipedia.org/wiki/Lever

[Steve K]

Thanks for the comments. I was thinking of taming a big cam ( for the street). Mike the heads are the 192's with little port work. Basically 35 grit the intake and polish the ex. The pinch was opened a little. I had considered a solid tappet with the mensioned specs. and figuered a hyd. with Rhodes would be the way to go. I'll stick with the solid.How drivable is .250 @ .050 on a 395 cu.in mtr. Probably not to much....never been down the road.

I ran a hydraulic roller ran a Bullet cam 252/254 with 114 lsa (originally made for EFI in a 406) in a 383 sbc with a 5 speed and no issues as far as streetability goes...and that's with a tunnel ram