8 inch double disc or 9 inch single disc clutch ?

danbalz

danbalz

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So I have my trans out for repair. Northstar engine came with stage 4 -9 inch clutch package that is in good shape but the pedal pressure is very heavy. My friend gave me a 8 inch double disc set up with a stage 4 pressure plate that is also in good shape. I'm concerned about crank thrust damage with stage 4 pressure. Really tempted to install double disc with maybe a stage 2 or 3 pressure plate. Any input regarding what stage pressure plate would be adequate or just stick with my 9 inch setup ? BTW I do do some, but very little, clutch feathering 

clutch.jpg

 
In my opinion, I have ran both and the double disc has a much lighter pedal feel and is easier feathering the clutch. Can't speak to crank thrust issues with either clutch but it is a no brainer if it was my car. Double disc for the win!

 
Agreed with double disc.

You can change the "feel" of the pedal by changing the master cylinder size.

I would stick with 9".

I tore up my 8" double disc in 2 trips when I bumped the horsepower up.

 
Kennedy has recently updated their torque holding specs of their clutches.  not sure if this is just new testing procedures that made the change or if the disc material has changed?

i would guess your non turbo motor probably nets less than 400 lb-ft of torque

single disc 9" 6 puck stage 3 holds 488, stage 2 holds 348

double disc 8" stage 3 has been upped to 654, stage 2-550, stage 1-448

you may confirm with Kennedy but that would mean a stage 1 or 2 8" could hold anything you put out and would be way less "crank thrust" pressures

if you are near 350 lb-ft then you could even get away with a stage 2 9"!

youre thinking is right on--less crank thrust pressure is good, especially for an engine that probably never had a clutch behind it--so the thrust may be whimpy!

 
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Weddle  9” single disc good for 450 ftlbs. Light pedal and you won’t find a smoother engaging clutch. Ran one in an LS/2D combo in a 2700 pound car with zero issues. 

 
The Dual disc of the 8'' is a glued pad and cracks between the pad,  the 9'' is the way to go,  

also the 9'' kennedy pad can be repucked when used for around $65.00 

 
Sandkist said:
Weddle doesn’t have stages. Good for 450 ftlbs. Maybe @Sean@Weddlecan add some more information.
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Our Weddle 9" single pressure plate uses centrifugal weights to increase the spring pressure on the disc as the engine increases RPM. Idle speed has similar feel to a KEP stage 3 pressure plate. High RPM should be a bit more than KEP stage 4. 

Unfortunately we have had to discontinue the Weddle 9" clutch line. Production prices went through the roof and they were going to cost double what the KEP would. Bummer because they were/are a good clutch. People just aren't willing to pay that much for them.

We are still however making the 9" single discs with sprung hubs. Those are somewhat popular and will fit inside a Kennedy flywheel and pressure plate. Lots of Class 10 cars use them. They also have a bit more forgiveness when letting the clutch pedal out, they don't grab quite as hard. But they are certainly more expensive than the KEP discs.

 
Sean@Weddle said:
Our Weddle 9" single pressure plate uses centrifugal weights to increase the spring pressure on the disc as the engine increases RPM. Idle speed has similar feel to a KEP stage 3 pressure plate. High RPM should be a bit more than KEP stage 4. 

Unfortunately we have had to discontinue the Weddle 9" clutch line. Production prices went through the roof and they were going to cost double what the KEP would. Bummer because they were/are a good clutch. People just aren't willing to pay that much for them.

We are still however making the 9" single discs with sprung hubs. Those are somewhat popular and will fit inside a Kennedy flywheel and pressure plate. Lots of Class 10 cars use them. They also have a bit more forgiveness when letting the clutch pedal out, they don't grab quite as hard. But they are certainly more expensive than the KEP discs.
Click to expand...
I happen to have a very lightly used PP, disc and flywheel for sale. :classic_biggrin: :peace:

 
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