Can someone school me on the pros and cons between a 3 finger pressure plate verses a diaphragm? I have an 11 inch in both for my Pontiac project and I’m wondering which direction to go? Thanks in advance. Sent from my iPhone using The H.A.M.B. mobile app
I looked up the 3 Finger Hayes and the static pressure is rated at 2750. I’ll have to look up the Mcleoud diaphragm tomorrow. Sent from my iPhone using The H.A.M.B. mobile app
It’s all about the springs and how pressure is applied . For the a street driven car you are going to appreciate a diaphragm set up where the low finger count is going to hold more pressure which is better for racing.
With a 3 finger pressure plate you may want to sleeve your clutch linkage. I put one in a O/T L-88 Corvette that I had and the clutch rod from the pedal to the cross shaft started to flex. So I sleeved that and then the rod from the cross shaft to the throw out fork started to bend. Ended up with my left leg bigger than my right. Finally went dual disc and a diaphragm. Much better for the street.
Putting a new Hayes clutch & pressure plate assembly in my 64 when I upgrade the bellhousing and flywheel. I already have similar with no issues whatsoever by comparison to other. Very streetable. Sent from my SM-G973F using The H.A.M.B. mobile app
Diaphragm is about half the pressure needed for operation vs the fingers. Fingers is good for racing application, for street I always say diaphragm.
The only press plate that would fit in my " A " roadster with a 303 olds v-8 was a long style ( three finger ) It had way to much foot pressure for the street and was bending the clutch fork and linkage . I removed it and sent out to FORT WAYNE CLUTCH , in Fort Wayne , Ind. They rebuilt it and installed lesser springs ( bench tested at 1650 foot pounds static ) It works great and was very reasonable pricing . phone them at 800/ 258 8243 . I worked with LOU good people !
It might depend on how many ponies you're gonna need to hook up.....we know nothing about the engine, and intended use of the car, so we can only make wild guesses as to which one would be better. And we know nothing about the pressure plates in question, there is a wide range of specs for both types.
I have run stock configuration gm spec pressure plates since 1963 . I've used flat finger diaphragms , raised finger diaphragms & Borg ,& beck styles . Given that the linkages , throwout bearings& forks as well as pivot ball were all correct for the application & working properly , there was a VERY small difference in pedal pressures . The flat diaphragms had an over-centering problem at high rpm , the raised diaphragms seemed a bit " smoother" , the three fingers seemed to have a more " positive" feel . I did not "feel" any holding power problems .
squirrel, The car is a 60 Catalina sedan, shipping weight is 3600lbs The engine is a stock 389, 068 cam, flat top piston, 4bl intake factory rated at 303hp minus later cam, factory headers and ignition. GM 4spd (Muncie or Super T10) 3.42 rear end. It will be a street car but Famoso is about 20 minutes away and I do plan to run the car with slicks. Car came factory with a 3 finger gm clutch. I have an 11 inch Hayes that is rated at 2750lb. I also have a McLeod 11 diaphragm rated at 2400lbs. (I was cleaning out my garage an found them from other projects) I’ve driven my 57 Sedan with an 11 inch 3 finger clutch for years as my daily driver so that part doesn’t bother me but which one would you think would be a better choice for the Catalina and why? Thanks Scott Sent from my iPhone using The H.A.M.B. mobile app
Sadly due to the year cut off everything. But I won’t tell. Sent from my iPhone using The H.A.M.B. mobile app
I use a McCleod that appears as a Borg and Beck with rollers from one of their other designs. I’ve had it in my lakes roadster for 5-6 years. I has a easy pedal which I needed and great clamping for my 4” stroke engine. It was recommended by them after I kept breaking the wave connecting bars.
Back in the very late 70's I had a HAYS 10-1/2" SUPER CONNECTOR clutch and Long style pressure plate in my 6 cylinder drag car. They were thinner and weaker than the 11" units and I ended up splitting the location windows in the pressure plate wide open, luckily I was able to weld in reinforcement strips to overcome it happening again. Their advantage is the ability to tune/balance static and centrifugal pressures at varying RPM's.
Still looking for more detail on the pros and cons of both. A friend of mine runs a 3 finger that he had the spring pressure reduced quite a bit in his 57 150 and then went with a metallic disc. He suggested I do the same. Sent from my iPhone using The H.A.M.B. mobile app
The harder the disc material , the more the other surfaces wear & the less " forgiving" the clutch is to operate. Unless you're racing , anything more than a stock clutch is overkill , IMO .In the 60's , many full size GM vehicles were 3500 lbs + - , many of the engines were capable of 400 + - lb ft of torque . The stock factory clutches held up fine on street tires & " teenage" drivers .
2old2fast, Thank you. That gives me a good reference point! I appreciate everyone’s comments as well. Sent from my iPhone using The H.A.M.B. mobile app
Pedal effort is lowest when released, and increases during clutch dis-engagement with a "3-finger" style Long /Borg&Beck pressure plate. The diaphragm's pedal effort is highest when released, and decreases during clutch dis-engagement. Price is also a factor; diaphragms are generally lower cost than multi-spring styles. Pedal efforts and cost are why production cars have all used diaphragms for the last 40 or more years.
Agree with most of 2OLD2FAST in his post above as long as there's no 6K+rpm "Banzai" runs. In years gone by I've seen too many of those stock clutches come apart, sometimes resulting in serious injuries. Many was the young guy who took his car, let's just say a '57 Chev. and installed a "Duntov" cam, solid lifters, and stronger valve springs out for a little street racing because the drag strip had outlawed stock flywheels and clutches with solid lifters. With his "3 on the tree" he missed the shift from 1st to 2nd and the flywheel and/or the clutch exploded. Hot shrapnel goes every which way and anything in the way is ripped apart, including feet and legs. Not pretty. That's when you need a non stock clutch and flywheel, and hopefully a scatter shield also. In my case I have a '31 "A" Hiboy with a potent SBC and 4 speed, street driven with maybe 2-3 times a year trips to the strip. I'm 83, with a weak left leg as a result of a back surgery that was delayed too many years. A clutch that I can handle with comfort and enjoy street driving will hold on street tires, but not when I put on the slicks. So I'm going to install a dual disc clutch and hopefully have the best of both worlds, a clutch that will hold the engine on slicks and be enjoyable on the street. Cars built from about '55 and later OEM equipped with manual trans usually have an over center spring built into the clutch and it helps a great deal to overcome the problem I'm having and you may be able to get by without such an elaborate (and expensive) setup, but I wouldn't use a metallic disc on a car I planned on street driving.
Yep, I'm referring to an over center spring in the linkage. I don't recall ever seeing a set of OEM swinging from above pedals that didn't have this spring, and it helps a bunch on pedal effort. Sorry I wasn't more specific about where the spring was
I dropped the pressure plate and the flywheel off at the machine shop this afternoon. After thinking about what southcross said about the clutch linkage and looking at the stock linkage )photo courtesy of a fellow hamber and Pontiac guy) I went with the McLeod 11 inch diaphragm. Thank you everyone! Scott Sent from my iPhone using The H.A.M.B. mobile app
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