Granny

If you have a manual trans and can pull off minor fabrication, here's a simple way to get more power thru your stock rear axles.

Just a simple, commonly available, hydraulic storm door closer cylinder installed on the clutch pedal. It allows tuning a bit of "slip" into the clutch's initial engagement, damping the peak shock loads as power is being transmitted to the rest of the drivetrain. It's adjustable for exactly where in the pedal travel that it becomes active, and adjustable for rate of release from that point on (it controls slip only during the final part of engagement). The cylinder is hydraulic (not pneumatic like most), with characteristics similar to those of a 90/10 shock, pulling the rod out is easy, only the return stroke of the cylinder is controlled. With the hillbilly style slipper installed on a clutch pedal, the final bit of clutch pedal's release is delayed, not the whole release cycle. The rest of the clutch pedal's travel works like normal. During normal driving you will not even know it is there...no detectable difference in clutch feel. If you are using the clutch pedal during shifts, the slipper will soften drivetrain shock during gear changes as well.

I first came up with the idea back when we were drag racing using Saginaw 4spds. We went thru a lot of them and could pretty much predict which gear was going to fail depending on which ratio gearset was in it. After playing with the hillbilly slipper, we quit breaking gears in the Saginaws, and were able to get the 60's down to 1.45 before we started twisting mainshafts. My experience is that the Hillbilly Slipper is not going to help much after you start twisting mainshafts.



How does it work?...
...Basically when the clutch pedal is depressed, it pulls the rod out of the cylinder. When released, the clutch pedal comes out unrestricted until the nuts on the cylinder's shaft contact the dash bracket. From that point, the rate of release is controlled by the adjustable orifice inside the cylinder.

How is it adjusted?...
...Adjusting the nuts on the threaded portion of the shaft changes the point in the clutch pedal travel where it's release is delayed. From that point, turning the dash **** changes the speed of the pedal's final bit of release. There are 10 turns of adjustment on the ****. At "0" turns the pedal is delayed very little, barely noticable. At "10" turns, the pedal takes about a minute to return. Typically, the rate of release is usually set between 2-1/2 and 4 turns.
When adjusted to protect your drivetrain... the slipper's main function is to delay/soften the clutch's final engagement, effectively damping the peak shock loads that the drivetrain will see.
When adjusted for making a fast pass at the strip... the slipper will delay clutch hookup, allowing the engine to spend more time operating closer to it's power peak. If the clutch grabs too quickly, it will pull the engine down, away from it's power range, every time the clutch is released. While experimenting, I found our car to be much quicker when the clutch was slipping a little more than I liked. I found the optimum slip to be one that did not pull the RPM down during launch, but allowed the engine to go straight to it's power range and stay there without activating the shift lite prematurely.



It's affordable too...
...The only change made to the $15 hyd cylinder was to add a section of 5/16" all-thread to the end of it's shaft. The slipper works on both mechanical and hydraulic clutch linkages, as it directly attaches to the clutch pedal itself.
Below are some pics of the parts we used on our project. They were all purchased at our local Lowes's Home Improvement...



...Wright Products VH440BL medium duty door closer
...Hilman 881357 bar **** (5/16" x 18)
...5/16 x 18 "all-thread" (comes in 3' lengths)
...5/16" x 18 flange nut
...5/16" x 18 jam nut
...Delrin plastic (for making the dash bracket slide bushing)
above items likely less than $50 at your local hardware store.

The VH440BL actually comes with attachment brackets that could be modified for use on a clutch pedal, but I made the bracket that attaches to the clutch pedal from scratch.

Here's a link to a more refined version......Clutch Slipper

Here's a link to an install & tuning guide Clutch Slipper Install & Tuning Guide


If you would like to quit breaking transmissions or stock rearends, installing a Clutch Slipper just might help.

AlkyIROC

It's a bandaid fix. Instead of applying quick and instant power to your tranny and diff, you just wear out your clutch faster.

jmd

iTrader: (4)

Spinning tires isn't speed.

And I could see where the engine not being bogged down helps E.T. at the possible slight expense of MPH.

Interesting mod.

Granny

Sounds like you are an automatic guy.

With a manual trans, before you vehicle speed catches up with your engine speed, either your clutch has to slip or your tires have to spin. You will typically be faster if your clutch slips, which allows your engine to quickly get into it's power range.

Granny

No expense of mph, the added slipping only lasts for an added 1/2 to 1 seconds, you have full pressure plate pressure after that.