Has anyone had shifting problems with a centerforce pressure plate at 7000 or 7500 rpms? I picked up a centerforce Pressure plate for use on my son's smallblock Nova but a good friend of mine says they are no good for high rpm shifts because they distort and won't let go of the disk--anybody run into this problem? He recomends a B&B adjustable. I need to nail down which to use so I can get the balance work done. This car will mostly see street use but it sure wouldn't be any fun if it doesn't shift when spun up. Bob

ttt?

ttt?

Yes I have heard that too although it seems to be when the weights come loose or move on pressure plate ..can be a CF problem then again it does not happen with every CF clutch some work fine ....you may want to check out a McLeod diaphram clutch they don't use the same system ..call then before you decide you need a B&B

Bob,
All of the diaphram clutches are prone to problems at very high rpms. They can go "overcenter" and stick in the disengaged position until the rpms drop. If you are serious about running 7500 rpm, you should consider a three finger type clutch. Its been a while since I raced a stick car, so you may want to call a couple of the clutch manufacturers to be sure. I used to run a Hayes 3 finger setup in my Chevelle and never had any problems. My left knee still hurts 15 years later from the pedal pressure smile.gif Whenever I manage to get it back on the road with the Doug Nash 5 speed, I think I am going to try the Mcleod dual disc street setup.

The problem of clutch sticking to the floor is because of too much pedal travel. Either adjust the clutch so when fully depressed there us about .030 between the disk and flywheel - or - put a stop on the pedal so the pedal doesnt go all the way to the floor. One of the old tricks with a diaphragm clutch was to screw a block of wood to the floor under the pedal to keep the pedal from going too far down.

makes sense

Bear in mind that I'm a novice racer, but I did have a problem last year at a late season T-n-T. They were hot lapping us ( if you wanted) and I did four back-to-back runs. missing the 1/2 shift on 3rd run. And 2/3 on the 4th. Come to find I should have let the clutch cool down between runs. Makes sense.

Another solution for overtravel, which I did not effect, is to relocate the clutch pedal rod 1/2" lower on the bracket. The only trick is to grind through the casehardening on the bracket before you drill.

Again, I simply could have been getting "jitters" ( it was running really close to 11's ), but I've never missed a 7K shift on the street.

(BTW, I'd pay special care to the balance and concentricity of the flywheel/clutch setup for 7500rpm shifts!)

Other than that, the pedal pressure, 'grab', and the longevity ( had 10K on a 10 spline cltuch pulled when I went to 5 speed - and it looked mint), really makes the CF hard to beat. I think the weights may make a little 'rattling' noise. But I've been feeding CFs big block * 7K shifts for around 30,000 miles now. graemlins/thumbsup.gif

..and plan further testing... graemlins/waving.gif


*( first interation a freckle under 500hp, second iteration right at 500 , 1st shifts were at 7000+, 2nd iteration >6800 rpm, so shift points went down as power went up; to evaluate the results vs. power properly )

Yeah, I've heard the centerforce units do rattle when first started until the weights locate themselves. A good friend of mine with a 440 cuda runs the CF setup without any trouble but was clueless as to what the rattling sound was when the combo was new. He crawled under the car and had his son start it while looking up through the bellhousing inspection opening. He found that the weights take an oval shape at startup then go round when they locate themselves. I don't think this noise will bother me as long as I know what it is. Bob

I ran the Dual-Friction complete clutch setup for years in my Camaro behind a small block and big block, and never once had any problems. When I powershifted, I just tapped the clutch though. I normally shifted around 6500 but it seen over 7000 every once in a while. I thought the locks around the diaphragm prevent the plate from collapsing at high rpm. :confused: I don't know, all I know is I put 3 different type Borg and Beck clutches in, and after about the 3rd holeshot, they were dead. I went through 3 trannies before I took out the clutch to switch to an auto, and it still looked like new. Probably only had around 2000 miles on it though. :rolleyes: I did miss shifts every once in a great while, I just thought that it could be a linkage problem or a OPERATOR problem ;) graemlins/angry.gif Boy there's nothing like a missed shift at 6500+ rpm! You watch for pieces coming out behind you. Never seen any though! tongue.gif