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I've been running my McLeod Soft Lok adjustable clutch for many years and it's been great. It worked perfect on the street as well as at the track...especially well when I was N/A. I could launch at 5000-5500 RPM and just start grabbing gears. Once I added the turbos and a few hundred more HP....things got a little trickier. The previous combination of base pressure and centrifugal assist couldn't hold things. I could launch well but once boost hit it would try to "drive through" the clutch. I added more centrifugal assist to help...but it wasn't enough...so the only recourse was to add base pressure. This makes it a lot more violent and prone to wheelspin and/or wheelies. I finally had to resort to launching at real low RPM...almost bogging it and then making it pull back hard to get down the track. NOT the quickest way to do things. But at the end of the day I was able to manage a 9.10@162 MPH that way.
I decided to send my clutch to Cale Aronson at Black Magic Clutches. Cale is a former Pro-Stock racer who was injured in a racing crash and now alternates riding a wheelchair or a walker. He and his wife have parlayed all his experience and equipment into building clutch combos for folks. You see a lot of his stuff on Drag Week and in some of the fastest stick shift cars.
Initially we planned to do some upgrades on my assembly...but when it was all said and done it was time to step up a little. I'm well past what McLeod says the Soft Lok is designed for especially considering the power, weight and poor gearing I have (which still allows those 200 MPH TX Mile runs!).
Cale put together a combo utilizing an 11" disc vs the old 10.5". It uses a billet pressure plate with segmented steel wear plates to reduce heat warpage. He also used different levers to apply pressure more in keeping with how a turbo car responds and we'll be using at least double the centrifugal assist I was able to do previously. It utilizes 6 internal springs vs the previous 9 springs to allow a finer adjustment range once I get to a near perfect tune. I'm also using an aluminum flywheel this time vs the steel one I've always used. I need to be able to come out at higher RPM and not hit the tires so hard...so it should help.
We had one communication hiccup in the process with Cale being out sick a few days and his wife Tinzy assembling the unit. I received the wrong springs that were too soft. To save time shipping it back and forth, he just shipped me the new springs and I installed them. I also re-checked and reset all the lever heights. To give you an idea of precision...the shims under those lever stands range down to .003"!!
So it's all back together now.....time to get to the track and try a few test hits on slicks to see where we need to go on the tune. Should be fun and eventually I'll nail an 8.99 time slip out of this thing!
JIM
Last edited by 427Hotrod; Oct 19, 2019 at 12:09 AM.
Man that video from the interior is amazing. It goes like a rocket sled. It looks like you have your line lock button on the steering column. I was wondering why you don't have it on the shifter.Thanks for posting Jim.
Man that video from the interior is amazing. It goes like a rocket sled. It looks like you have your line lock button on the steering column. I was wondering why you don't have it on the shifter.Thanks for posting Jim.
It's on a coiled cord that plugs in under the dash.....I use it and then toss it aside. When not racing I unplug it and remove.
Jim, how do you build up the boost at the staging lights or are you doing just the rpm launch?
Right now I'm launching off boost. I can use the "boost builder" function in the Holley EFI to build it...but when I tried it, it was really violent crazy with the tight clutch setup. And that was only with 2 PSI!
I actually need to use boost builder but then setup the progressive boost control to manage things...but until I get clutch sorted out it won't help any.
Took the 'Vette out for some little shakedown passes with the new clutch. Works well!
Of course it was just some launches on pumped up cold drag radials on the highway...but felt good. It shifts clean and no slippage as RPM climbs. I've got a lot of centrifugal assist on it...so it's holding well. Ran it up through 7000 RPM shifts and 130 MPH or so a few times...
Did have some popping under boost. Came back home and backed off the timing and actually leaned it a little and it did a lot better on next hits. Guess 93 octane that's been in the tank a few months isn't what it was when first put in huh? Still had a little roughness up there...but revved a lot cleaner. Plugs still look rich but safer fat than lean and hard to tell if gas is funky. Kept boost to about 17-18 psi..so not too radical.
Sure is fun to play!! Time to get it to the track on some slicks and make some passes!
New Racing Clutch
