Anyone use these? I'm considering getting kit #413753040 through Summit. Seems like the easiest way to get all I need to have a setup that'll hold and work with my to be built 8 bolt flange 508" stroker RB.

Im running a twin disc clutch setup on my 540. I just broke my 18 spline 833. Everybody I talked too says dont run a twin disc, you want some slip or you will break parts... Didn't make sense to me, but i get it now.

Yup. Those clutches are parts breakers. But, you don’t want to slip the clutch. You want to control the application of the clutch. Big difference.

I run a DFX pressure plate with a DF disc.

The Racepak graph below is of a dragstrip pass with an engine that puts out around 425ftlbs max WOT steady state. I added some averaged binary torque numbers to the lower part of the graph to reflect the calculated torque that the engine applied to the transmission's input shaft during the pass.

Note how this 425ftlb engine put out way more than 425ftlbs when it is losing rpm, and much less than 425ftlbs when it is gaining rpm. At no time during this pass was this 425ftlb engine actually sending 425ftlbs to the transmission's input shaft, because at no time during this pass was the engine operating at a constant rpm. The engine was either losing or gaining rpm at every point while it worked its way thru the gears...



To wrap your head around this, you need to think of the engine's rotating assy as a torque storage device. Some of an engine's torque gets absorbed by its rotating assy as it gains rpm, then that absorbed/stored torque gets released as rpm gets drawn out of the engine's rotating assy.

From there you need to understand that the rate that the clutch draws the engine down is what controls how that stored torque gets applied to the transmission's input shaft. Using nice round numbers to make it easy to grasp the inverse relationship, let's say a rotating assy gains 3000rpm in 1 second while absorbing 200ftlbs of torque during the engine's climb to the 1/2 shift point...
...If the clutch then draws out the same 3000rpm over the same 1 second time period after the shift, 200ftlbs gets added back to the input shaft torque for 1 sec.
...If the clutch then draws out 3000rpm over 0.5sec (half the time), 400ftlbs of torque (double the torque) gets added to input shaft torque for that 0.50sec.
...If the clutch then draws out 3000rpm over 0.25sec, 800ftlbs of torque gets added to input shaft torque for that 0.25sec.
All three above examples of discharge rate release the same quantity of energy. Give the car 200ftlb "boost" for 1sec (200 x 1 = 200) vs a 400lb boost for .5sec (400 x .5 = 200) vs an 800lb boost for .25sec (800 x .25 = 200), it's all the same amount of boost from returning energy.

Given that a 3000rpm discharge releases the same quantity of energy regardless of how fast you lose the rpm, you have to ask yourself how much additional torque can your drivetrain/chassis efficiently handle? If you throw an additional 800ftlbs at it for 0.25sec, is it going to break something? Can the shocks handle that hit? Are the tires going to be shocked into excessive wheelspin and waste a large portion of the returned energy?

When you just bolt in a typical non-adjustable clutch, you are pretty much locked into whatever rate it might pull your engine down against WOT. There is no advantage to buying a clutch that pulls 800ftlbs out of a 425ftlb engine's rotating assy. Don't buy a clutch with plans to "grow into it", pick one that's the best match for your engine and use. Not a situation where too much is just right. Excess torque capacity not only increases the clutch's potential to inflict damage on your drivetrain, but it will also slow you down at the dragstrip.

Grant