Clutch for Small Block?

MJN · #1 (**permalink**) 10-27-2002, 03:03 PM

So I had my car dyno tuned last Tuesday and they found over 80 ftlbs of torque and more than 60 HP with revised tuning and fuel curve. So that's good right? Well it was until yesterday when I took the car out for a little 'fun' and 'drove through the clutch'. I have a Ram HD clutch in the car now that was fine for 350 ftlbs but now with well over 400 ftlbs it's just not cutting it. Even though I can still drive the car the clutch lining is fried as it stinks every time you slip it at all.

I really liked the pedal pressure of the RAM clutch and its driveability but I need to upgrade. Can I get a clutch (driven) disc that has a higher friction coefficient that will give me more torque capacity with the same pressure plate? If not what's a good street clutch that will take 450 - 500 ftlbs of torque at the flywheel?

David Kee · #2 (**permalink**) 10-28-2002, 04:21 PM

What part numbers do you have? You could go to the powergrip disc with kevlar on the flywheel side if you just have the standard organic linings now.

David Kee
http://www.4speedtoploaders.com

MJN · #3 (**permalink**) 10-28-2002, 06:59 PM

David

I have the standard organic lined clutch, the RAM part number (for the clutch set) is 88794HD. How much better would the 98794HD Kevlar clutch be? I called around and also got a recommendation for the FMS HD Dual Friction Disc (7550X302). Which would be better? If I can just get away with replacing the clutch disc for now that would be great but as with everybody on this forum I am constantly looking for more power so I know sooner or later I will have to upgrade the entire unit probably to an 11" diameter assembly.

Thanks

David Kee · #4 (**permalink**) 10-29-2002, 08:47 AM

I will be talking to Ram today about some other stuff. I will find out what would be the best way to go with your setup. I should know something by the end of the day.

MJN · #5 (**permalink**) 10-29-2002, 09:01 AM

David

Thanks for the help. I really appreciate it.

David Kee · #6 (**permalink**) 10-29-2002, 10:42 AM

Mike,
I just got off the phone with Ram. With the power you are running you will have to step up to a much higher grade clutch. They are talking changing the complete setup to more of a street strip setup. They did not recommend changing just the disc because the pressure plate has seated to the disc in there now. The life of the new disc will be very short because all of the pressure plate will not be contacting it. If you need to call me you can reach me toll free at 877-276-8081.

David Kee
http://www.4speedtoploaders.com

Mr.Fixit · #7 (**permalink**) 10-29-2002, 02:02 PM

I run McLeod kevlar lined disks in 500+ small blocks, no problems.

MJN · #8 (**permalink**) 10-29-2002, 02:18 PM

Mr Fixit

Do you have a type/part number for a 10.5" McLeod Kevlar clutch? Is it a diaphragm clutch? How's driveability? Does it chatter/grab?

Thanks for your help

Mr.Fixit · #9 (**permalink**) 10-29-2002, 03:21 PM

You ought to just call Red over at McLeod, he'll tell you more than you needed to know. The one I have listed (in front of me, not at home in the toolbox file) is 260830 which, if memory serves correct is a 10.5" 10 spline (tremec 3550) kevlar faced 800 series McLeod disk. Call McLeod to get the right number for your app, along with a pressure plate, and scattershield if you don't have one allready. Drivability is great, no chatter, better engagement than any 2 disk clutch I have driven.

Mr.Fixit · #10 (**permalink**) 10-29-2002, 03:24 PM

Forgot these numbers:

pressure plate 360048
flywheel 563100-28 (for external balanced windsors)

But really, call McLeod, they will make sure you get what you need

David Kee · #11 (**permalink**) 10-29-2002, 03:35 PM

Mike,
If you go with McLeod get your part numbers and give me a call. I sell their products at jobber, it should be about 20% less than they quote you. I think Red will agree that 500 ft. lbs of torque with a blown motor is a little much for a single disc with kevlar on one side. I'm not saying it won't work, I'm just not sure how long. Get several opinions and spend your money once.

David Kee
http://www.4speedtoploaders.com/mcleod.htm

MJN · #12 (**permalink**) 10-29-2002, 03:38 PM

Thanks. Mr Fixit I'll talk to McLeod.

I got a good response from Mike Norcia at RAM already. I guess I really need to upgrade everything from the flywheel back and add a scattershield. So as it'll take some serious gas money I want to make sure I only do this once. RAM also pointed out that my 3.08 rear gear wasn't helping the situation much either. More gas money! Hmmm? now how do I get this one past the financial committee? (Wife).

MJN · #13 (**permalink**) 10-29-2002, 03:46 PM

David Thanks for the input.

As the weather has all of a sudden turned into winter here (it was just sleeting outside) I have a couple of months to sort this out before spiringtime. I will talk to McLeod and compare notes with what I was told by RAM. Beyond that unless there's an obvious technical reason (advantage) to go one way or the other it'll probably come down to price.

At the moment the RAM 900 series clutch with their aluminum flywheel sounds like what I need. Add in a scattershield and that's over $1000. As I said before that's a large investment and I want to make sure I make the right choice. Any further input would be welcomed.

David Kee · #14 (**permalink**) 10-29-2002, 04:15 PM

I also talked to Mike at Ramhe is a good source for information. I just started selling Ram products, they seem to have a wide range of clutches.

David Kee

RACER X #99 · #15 (**permalink**) 10-29-2002, 04:29 PM

No clutch expert here but I really like the Dual friction Centerforce behind my 351 windsor.(before it blowed up) Nice soft pedal and it never slipped on me.

Cranky

speed220mph · #16 (**permalink**) 10-29-2002, 04:53 PM

The Dual Friction clutch is a good choice because as the disc (that's the dual friction part) heats up, the friction of the metalic side increases to make up for the friction lost on the organic side, causing the clutch to hook up better. Regardless, you still need plate load to clamp the disc, so a dual-disc clutch will provide the torque capacity while keeping pedal effort at a managable level.

MJN · #17 (**permalink**) 10-29-2002, 06:52 PM

speed220mph.

I don't really want the weight of a dual disc clutch, I'm already thinking of going to an aluminum flywheel to reduce the drivetrain inertia. And a circle track small diameter multi disc clutch is probably not going to to work too well on the street.

The dual friction clutch disc sounds like a good bet and will be considered along with the centerforce. The problem with the characteristics of the centerforce and the torque curve of my motor is that the centerforce increases clamping load as the rpms increase and my motor puts 412 ft lbs of torque to the tires at only 2300 rpm so I don't think it would be as effective as it would on say a 7000 rpm open track car. I really need a clutch that has a higher coefficient of friction and a higher clamping force or the right combination of the two. And as far as I can tell that is going to be the trick, to find the right pedal pressure, not too high, and the right coefficient of friction disc that is not too grabby or harsh.

Good inputs, thanks guys....

speed220mph · #18 (**permalink**) 10-31-2002, 09:54 AM

The "trick" here is to go with the dual-friction disc and an unweighted pressure plate, thus there will be no increase in plate load, i.e., pedal effort, at high rpm, or over 6,000 rpm. I don't recall whether Centerforce offers an unweighted pressure plate, but that's what you will need if you're going to shift at higher revs. If you'll be shifting under 5,500 rpm, a weighted pressure plate is ok.

As for an aluminum flywheel, it will work since the Cobra is light and the final-drive ratio is 3.20:1 or higher. Otherwise, you'll need the extra inertia to launch the car.

MJN · #19 (**permalink**) 10-31-2002, 05:39 PM

Thanks Tom.

You know without actually being able to sample all the various combinations of pressure plates and clutch discs it's a difficult decision and everyone has their own experiences and preferences. I guess what I've learnt from these posts is that I will probably be OK with a number of different clutch set ups for what I have right now. I just "came by" a new center force dual friction clutch disc from another club member that will be gong in in the next week or two. I'll see how that lasts and if it doesn't then I'll be going all out for a sintered iron clutch that will take more than 600HP. Both RAM and McLeod have set-ups that I am told are streetable.