I found the limit of the stock clutch...

[nbuscemi]

I am using a run-of-the-mill replacement clutch in my 68 Sedan. Recently I've been playing with the launch control / no-lift shift features of my Megasquirt EFI. Turns out (insert sarcasm here) the stock-is clutch slips like heck at 5K+ rpm and 10 psi pf boost. Long story short, I need a stronger clutch. Problem is, there are too many options. I need input from the masses...

Specs: 1600cc EFI / Turbo (130-140 WHP)
1973 single side cover transaxle (stock as far as I know)
Cheap-O street tires on steal wheels, no slicks
I need something street-able but with enough bite that it won't slip on hard-ish launches.

I was looking at the KEP stage 1 1700lb with CB Super clutch disc (solid hub).

What do ya'll think?

-Nick-

[buguy]

Might take a look through Clonebug's thread. I believe he tested that exact combo.

[Schweg]

I can a stage 2 and exedy disk no issues with my 1600 at 24 lbs of boost and bigger Baja tires.

As long as your below 250lbs of torque your options are pretty open!


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[madmike]

He's only got 140 hp ,,a stage 1 with that cb disc

[Lo Cash John]

Keep us posted if you use the CB super disc. My buddy went with a stage 1 (1700 lb) and a CB (it's actually made by CenterForce) dual friction. It's way quicker to engage but still very drivable.

[nbuscemi]

Sadly CB is out of stock on all of their KEP pressure plates. The "Supply Chain" problem is really getting out of hand. Seems like anything anybody wants or needs is on Intergalactic Back-order.

-Nick-

[Clonebug]

My Kennedy Stage I and CB Super Disc held until about 23 lbs boost on my 1679. It would hold at least 180 whp and 200 lb. ft of torque on the Wheel dyno at 20.5 lbs.
I ended up swapping to a Stage II and using the same disc. I did shim the PP out .031" to increase the holding power to 250 ft. lbs torque on my torque wrench. It hasn't slipped since.
I've done some pulls as high as 26 lbs boost on the street and no slippage that I could detect.

[Ol'fogasaurus]

Clone, maybe I am missing something but if the flywheel is turned correctly the shimming shouldn't be necessary. The "stepped" style of flywheel, if turned correctly, should have both the PP mounting off-set distance and the disc area both turned to the spec. distances required.

Having the flywheel turned and forgetting to turn the PP mounting area also is not unusual so after turning the off-set distance should be checked just as a precaution.

Lee

[buguy]

It has more to do with the thickness of the disk.

[Ol'fogasaurus]

That is why I had my lightened flywheel turned to fit the combo of a 4 puck with a stock PP so no need to shim.

Shimming as I understand it, and depending on how it is done, doesn't always work well especially under heavy loads.

Lee

[buguy]

So every time you need a new clutch disk, you buy and turn the flywheel?

[Ol'fogasaurus]

So every time you need a new clutch disk, you buy and turn the flywheel?

It happened once and not since. Since I don't abuse the clutch in such things as racing and I had been trained from the start not to slip the clutch, getting the flywheel turned properly pretty much solved the problem. As I remember (this was back in the 90s, both surfaces did have to be turned as the two surfaces were slightly wrong and the cutch disc had made some dirty pictures on the flywheel. I take a look at the flywheel and if it needs to be turn'd I make sure all surfaces are properly done if needed.

When I was (supposedly) being trained to be a mechanic back in the mid-60s getting the two surfaces correct was a problem as not everyone thought of or were used to it... they just dressed the flywheel where the different things had happened and gave it back. I have seen some very badly dam(n)aged flywheels in my time.

You build an engine... you do it right. The connection to the trans is still part of the total package build so you do it right.

Lee

[buguy]

Lee do you run a turbo?

[Ol'fogasaurus]

Lee do you run a turbo?

leecar30 - Copy.jpg

I have had a lot of cars and I mean A_LOT of cars but never ran any kind of "puffed" engine but I have had several fairly high horsepower engines in the past.

leecar13 - Copy.jpg

In '67 I had a 390 cu-in 4-speed Mustang that my now ex-wife over time warped 3 flywheels on it (Ford said they would not cover the flywheels warranties after the 3rd warped flywheels). I was in the hospital at the time having my first of 4-cornea transplant and if you have ever been to Seattle it is pretty hilly (especially on "Pill Hill" where most of the hospitals were) and many of the hills are very steep plus they often have stop lights on them. She had never driven a stick engined car before. I learned how to "deck shift" with this rig.

Whenever you replace a disc or PP or even a throw out bearing you always should look at the condition of the flywheel and all components.

Also, street racing, "rat racing" (kind of like "drifting" but not the same) or just "squireling around" is not only not safe but ill-legal in most areas. I have had a few friends lost over doing silly stuff like that and I almost hit a staggering drunk lady who suddenly jaywalked in front of me.

Lee

[gbaker770]

It’s the old “ bolt it together and run it” theory. Then you hear the “ my stage 4 and 3 puck slipped at 10 psi on my 1641”. Proper clutch/flywheel setup rarely happens. Most people check the torque and shim to get the breakaway they want and call it good.
I can tell you a stage 1 and 4 puck holds over 370 whp on the dyno with multiple pulls and will run consistent 6.70’s and 10’s in an 1800+ lb street car on DOT’s if setup correctly.

https://youtu.be/18rNp_oj7m8