New clutch setup won't disengage

[DrCharles]

I have a Centerforce Dual Friction clutch setup on a new 10.5" steel flywheel. I fabricated a hydraulic linkage with a Wilwood master and a pull-type slave cylinder to a conventional fork/throwout bearing. It's inside a Lakewood so there's not much of a view other than through the fork hole.

I mounted the clutch onto the flywheel at least three years ago if not four (it took me that long to complete the car to the point where I could drop in the drivetrain, fire-up and break in my new 451). So yesterday I finally fired it up and broke in the cam... but could not put the car into any gear with the engine running! Shifts fine with it off. It occurs to me (and I've seen it in the past with all-organic discs) that the disc could be stuck to either the flywheel or the pressure plate from being clamped there for so long...

But I'm going to work through this logically. First make sure the air is all bled out of the system! Then measure the actual travel at the fork (I have almost all the slack adjusted out, just enough to keep the throwout bearing off the clutch fingers). It's possible that I need to redo the pushrod mounting to the clutch pedal but it feels sufficiently "heavy" that there should be plenty of plate departure.

Finally if I determine that the disc is actually sticking, I plan to jack up the rear, start the engine and while idling in 4th (about 20 mph wheel speed), depress the clutch pedal fully and gently apply the brakes a couple of times. I definitely don't want to use the starter as an impact driver - a good way to break pinions, or even worse, a ring gear. I don't know that this is the problem, just thinking worst-case.

So I have a question - how much travel is there supposed to be at the actuating rod hole in the fork with a Centerforce DF? About one inch?

Also any other ideas for freeing up the disc would be appreciated...
thanks
Charles

 

[TrailBeast]

Firstly, you won't hurt the ring or pinion with the starter (If I understood that correctly)
I had a car that sat do that once and I blocked the pedal down and reached in through the fork opening with a long screwdriver and popped the disc loose, and everything was fine after that.
In your case you may have to pull the clutch out and reassemble it if you are not comfortable or able to do anything else.

Personally I'd be tempted to warm it up a bit to make it more agreeable then roll it out in the street, put it in gear and fire it up.
Of course you need to be ready and understand that it may just take off with the clutch in, but you can pop into neutral if needed.
It may come loose right then, or you might have to push the clutch in and jump on it a little.
I'd try that as a last resort before pulling it and reassembling.

I had to drive a car through town and about 15 miles home with a broken clutch fork once and I basically did it this way.
Put it in gear and fire it up to get it rolling.
Pop it in neutral at stop lights and stop signs and shut it down, then put it in gear again.
Then the light turns green and you fire it up rolling again.

What you want to do is fire it up in gear with the clutch in and jump on it a little.
It'll come loose if it's just stuck, but won't if it was an assembly problem.

 

[yellow rose]

I doubt the disc is stuck to both the pressure plate and the flywheel, which s what would have to happen to get what you say is going on.

With that said, when a car won't go into gear while it's running but will with the engine off, it's from a lack of air gap. The clutch is dragging.


So, get more air gap. Which is easier said than done with your bell housing.

Any reason why you went with a hydraulic clutch? I been around them and I prefer mechanical linkage if I can get it in the car.

 

[DrCharles]

I doubt the disc is stuck to both the pressure plate and the flywheel, which s what would have to happen to get what you say is going on.

With that said, when a car won't go into gear while it's running but will with the engine off, it's from a lack of air gap. The clutch is dragging.


So, get more air gap. Which is easier said than done with your bell housing.

Any reason why you went with a hydraulic clutch? I been around them and I prefer mechanical linkage if I can get it in the car.

Thanks for the input, guys ;)

Actually the disc does not have to be stuck to both sides to be dragging.

If it's stuck to the flywheel, even with the pressure plate disengaged, the disc will still turn...

And if it's stuck only to the pressure plate, that will also turn the disc since the PP always turns with the flywheel - the clutch cover is bolted to it and the PP ring doesn't freewheel...

Why'd I go with hydraulic? There is so little room between the header downpipes, t-bar, starter and frame that I don't see how I'd ever get a z-bar through there. Also less drag from pivots and bushings, so easier on the leg.
(I have the Lakewood, or course, because I like my right lower leg and foot to stay attached to me in the event of an explosion).

So how far should the fork be moving?

 

[DrCharles]

Firstly, you won't hurt the ring or pinion with the starter (If I understood that correctly)
I had a car that sat do that once and I blocked the pedal down and reached in through the fork opening with a long screwdriver and popped the disc loose, and everything was fine after that.
In your case you may have to pull the clutch out and reassemble it if you are not comfortable or able to do anything else.

Thanks.
I can do that, if I can bend a tool sufficiently to reach in through the fork hole. REALLY don't want to remove (Lakewood, BB A-body, headers).

Personally I'd be tempted to warm it up a bit to make it more agreeable then roll it out in the street, put it in gear and fire it up.

That certainly would work too, but jacking the rear end up means I'm not taking off down the road in a car that hasn't completed its shakedown and has no windshield, bumpers or lights

I'd try that as a last resort before pulling it and reassembling.

I had to drive a car through town and about 15 miles home with a broken clutch fork once and I basically did it this way.

I've driven A833's that way with a broken clutch pedal rod, too. And sometimes float the gears (without using the clutch) just for fun. Get the rpm's right and it just falls in.

What you want to do is fire it up in gear with the clutch in and jump on it a little.
It'll come loose if it's just stuck, but won't if it was an assembly problem.

That's basically my plan. AFTER I make sure I have enough fork travel...

 

[yellow rose]

Thanks for the input, guys ;)

Actually the disc does not have to be stuck to both sides to be dragging.

If it's stuck to the flywheel, even with the pressure plate disengaged, the disc will still turn...

And if it's stuck only to the pressure plate, that will also turn the disc since the PP always turns with the flywheel - the clutch cover is bolted to it and the PP ring doesn't freewheel...

Why'd I go with hydraulic? There is so little room between the header downpipes, t-bar, starter and frame that I don't see how I'd ever get a z-bar through there. Also less drag from pivots and bushings, so easier on the leg.
(I have the Lakewood, or course, because I like my right lower leg and foot to stay attached to me in the event of an explosion).

So how far should the fork be moving?

Well, I was clear as mud. Sorry. My point was if the disc is stuck to either the FW or the pressure plate, if the crank is turning but the input is not, the disc would have to be welded to one of them. Once the pedal is pushed down the input stops turning. I would think that alone would separate anything stuck together.

Used to have this issue on dirt bikes. I would roll along at slow speed, pull in the clutch and snap the throttle a couple of times to knock it loose. The same principal could be accomplished with the car at idle...

Naw crap, I'm losing it. You can't do that either.

Hell with it. I'm not being any help. Going to the range to pop off some rounds with my father in law. Maybe I'll get smarter while I'm at the range.

 

[SGBARRACUDA]

I've done this a couple of times. One time with a 59 Corvette many years ago. I did the same think your talking about, Put the rear on jack stands and ran the car in 4th gear, depress the clutch and hit the brakes. It took a several times and I ran it up pretty good like 50 mph and jam on the brakes. It finally broke loose.

 

[yellow rose]

I've done this a couple of times. One time with a 59 Corvette many years ago. I did the same think your talking about, Put the rear on jack stands and ran the car in 4th gear, depress the clutch and hit the brakes. It took a several times and I ran it up pretty good like 50 mph and jam on the brakes. It finally broke loose.

That's what I was trying to get at. Feel better now after 120 rounds of .45 and about 50 rounds of shot.

 

[TrailBeast]

That's what I was trying to get at. Feel better now after 120 rounds of .45 and about 50 rounds of shot.

Must be the therapeutic properties of gunpowder smoke.
I always fell better after blowing the crap out of something myself, but since National forest is 3-4 miles away we go out there.
We just try to stay from campers or day trippers, just because.

 

[DrCharles]

Glad you feel better after shooting, because this pre-shooting post made no sense:
"My point was if the disc is stuck to either the FW or the pressure plate, if the crank is turning but the input is not, the disc would have to be welded to one of them. "

The reason I can't get it into gear is that the input shaft has NOT stopped turning, because either the disc is stuck to the PP or flywheel or both, or there's not enough travel to disengage it fully. No welding required. In fact, for either of those two states, the only way that the crank can be turning and the input shaft not turning would be the input or disc splines being totally stripped out.

Anyhow I'm out of town all week, but when I return I will proceed as written in my initial post, and report my findings.

I'll ask one more time, since I can't easily measure plate departure, does anyone know how far the fork tip must travel to disengage the clutch?? Even on a stock B&B setup the distance is similar (the CF DF is supposed to be a drop-in replacement other than the overcenter spring).
Thanks!

 

[yellow rose]

Glad you feel better after shooting, because this pre-shooting post made no sense:
"My point was if the disc is stuck to either the FW or the pressure plate, if the crank is turning but the input is not, the disc would have to be welded to one of them. "

The reason I can't get it into gear is that the input shaft has NOT stopped turning, because either the disc is stuck to the PP or flywheel or both, or there's not enough travel to disengage it fully. No welding required. In fact, for either of those two states, the only way that the crank can be turning and the input shaft not turning would be the input or disc splines being totally stripped out.

Anyhow I'm out of town all week, but when I return I will proceed as written in my initial post, and report my findings.

I'll ask one more time, since I can't easily measure plate departure, does anyone know how far the fork tip must travel to disengage the clutch?? Even on a stock B&B setup the distance is similar (the CF DF is supposed to be a drop-in replacement other than the overcenter spring).
Thanks!

Yup, had my head firmly shoved up my rear.

Owning that, I'm not sure of the finger ratio of a diaphram pp. Somewhere I have written down the ratio for a long finger.

I would call Brewers and ask them. They should have the numbers. I would also think Center Force could tell you. You can legally drill a 1 inch hole in the bottom of your can and use a long feeler gauge to check it.

 

[AJ/FormS]

I think 1 inch is not enough travel.But it might just barely be.
Going from memory and guesswork;
If you figure the clamping pressure of the CF is 2800#, and your leg pressure is 60#, then you need a total ratio of 2800/60=about 47:1
I think the pedal ratio is about 7:1, and the Z-bar is Zero, so 47/7=6.7 left in the fork and pp. I'll guess the fork is 2.5:5.5, so 2.2, and 6.7/2.2 = 3:1 in the pp; and that looks doable.
Now then;3/1 x 2.2/1 x(.080+ say .060freeplay)= .924 travel at the outer socket of the fork,and going up the line, this would be 7 x .924=6.5inches at the pedal. Well I don't think you have that much, so maybe there is a bit more than Zero in the Z-bar.
Bottom line is 1 inch at the fork should do it.
Did I mention I'm going by memory and guesswork?

 

[yellow rose]

I think 1 inch is not enough travel.But it might just barely be.
Going from memory and guesswork;
If you figure the clamping pressure of the CF is 2800#, and your leg pressure is 60#, then you need a total ratio of 2800/60=about 47:1
I think the pedal ratio is about 7:1, and the Z-bar is Zero, so 47/7=6.7 left in the fork and pp. I'll guess the fork is 2.5:5.5, so 2.2, and 6.7/2.2 = 3:1 in the pp; and that looks doable.

Now then;3/1 x 2.2/1 x(.080+ say .060freeplay)= .924 travel at the outer socket of the fork,and going up the line, this would be 7 x .924=6.5inches at the pedal. Well I don't think you have that much, so maybe there is a bit more than Zero in the Z-bar.
Bottom line is 1 inch at the fork should do it.
Did I mention I'm going by memory and guesswork?

My thought was 1 inch on the fork was .110 on a LONG finger.

Crap, if there was someone here I'd measure it now.

BTW, I dont think my Z bar is 1:1

 

[TrailBeast]

My thought was 1 inch on the fork was .110 on a LONG finger.

Crap, if there was someone here I'd measure it now.

BTW, I dont think my Z bar is 1:1

With different length arms it can't be 1:1 and IIRC the top arm connected to the pedal assy is longer.
Percentage longer I couldn't tell you.

 

[AJ/FormS]

Yeah I think there is a bit in the bar,but I think it's the wrong way;I'll guess 3:3.5=about .86 , I's just having fun with math.....

 

[DrCharles]

I think 1 inch is not enough travel.But it might just barely be.
Going from memory and guesswork;[guesswork omitted]
Did I mention I'm going by memory and guesswork?

YR, no problem, thanks for the input. Are you sure a 1" hole is tech-legal even if no longer SFI certed (some day I may want to run it on an NHRA facility with good tech. Doubt it will be fast enough to require a blowshield but still)...

AJ, I did the same sort of guesswork and also came up with about 1". This weekend I am going to get under with a dial indicator, ruler, etc. while my GF pushes the pedal. I'd rather do it the other way round but she is not much for lying on the ground under cars!

 

[AJ/FormS]

Well,there's an opening line, If I ever read one;
but I ain't touching it!

But hey I just thought of something; What if the hole in the back of the crank was not deep enough, and the tranny input gear is jammed up tight against the crank I have heard of that happening with small-blocks

 

[yellow rose]

YR, no problem, thanks for the input. Are you sure a 1" hole is tech-legal even if no longer SFI certed (some day I may want to run it on an NHRA facility with good tech. Doubt it will be fast enough to require a blowshield but still)...

AJ, I did the same sort of guesswork and also came up with about 1". This weekend I am going to get under with a dial indicator, ruler, etc. while my GF pushes the pedal. I'd rather do it the other way round but she is not much for lying on the ground under cars!

Yup. It's legal. If you go 11.50 or slower, you can even run a stock bell. I am right now because I have to send my can back to Lakewood and have them put a window in the damn thing so I can tune the clutch. So you're ok with the 1 inch hole.

Just make sure you measure out from the block plate to the face of the FW and drill the hole. A buddy drilled his under the flywheel and it was about impossible to get a feeler gauge in there.

 

[yellow rose]

Well,there's an opening line, If I ever read one;
but I ain't touching it!

But hey I just thought of something; What if the hole in the back of the crank was not deep enough, and the tranny input gear is jammed up tight against the crank I have heard of that happening with small-blocks

That's a good point but I would think he would have had to pull the gear box in with the bolts to bind it that tight.

Could be tho.

 

[DrCharles]

but I ain't touching it!

That's what she said...

But hey I just thought of something; What if the hole in the back of the crank was not deep enough, and the tranny input gear is jammed up tight against the crank I have heard of that happening with small-blocks

I built a 383 once (from an automatic car) that had the recess in the crank and it fit the pilot bushing correctly, but not deep enough. I just took a large drill and deepened the bottom of the hole until the trans fit. Only time I ever saw one that had the right diameter hole but too shallow...

Doubt that's my problem though, because the trans slid right in, and did not have to be "pulled" in with the bolts or anything like that. Using a roller bearing in the crank flange, too. But if the hoofbeats don't turn out to be horses, then I'll start looking for zebras...

 

[yellow rose]

That's what she said...



I built a 383 once (from an automatic car) that had the recess in the crank and it fit the pilot bushing correctly, but not deep enough. I just took a large drill and deepened the bottom of the hole until the trans fit. Only time I ever saw one that had the right diameter hole but too shallow...

Doubt that's my problem though, because the trans slid right in, and did not have to be "pulled" in with the bolts or anything like that. Using a roller bearing in the crank flange, too. But if the hoofbeats don't turn out to be horses, then I'll start looking for zebras...

Watch out for the unicorns. They have no scruples.

 

[AJ/FormS]

Almost no creature does when it's horny.....
OOps did I say that out loud?

 

[DrCharles]

Got a one-line response back from Brewer's ("Wayne/Dan") : "You'll have to mock it up and see". Doesn't help much. Was hoping they knew the fork ratio, that would provide part of the answer. I sure don't want to remove it for measuring, because I might never get the throwout bearing reattached without pulling the trans!

Still waiting to hear from Centerforce as to how much finger movement is needed.
Anyway I'll be home this weekend and see how far the fork is actually being pulled.

 

[SGBARRACUDA]

Got a one-line response back from Brewer's ("Wayne/Dan") : "You'll have to mock it up and see". Doesn't help much. Was hoping they knew the fork ratio, that would provide part of the answer. I sure don't want to remove it for measuring, because I might never get the throwout bearing reattached without pulling the trans!

Still waiting to hear from Centerforce as to how much finger movement is needed.
Anyway I'll be home this weekend and see how far the fork is actually being pulled.

Proof positive that customer service stops when the money changes hands!

 

[yellow rose]

Got a one-line response back from Brewer's ("Wayne/Dan") : "You'll have to mock it up and see". Doesn't help much. Was hoping they knew the fork ratio, that would provide part of the answer. I sure don't want to remove it for measuring, because I might never get the throwout bearing reattached without pulling the trans!

Still waiting to hear from Centerforce as to how much finger movement is needed.
Anyway I'll be home this weekend and see how far the fork is actually being pulled.

I have found that Jamie Passon is very helpful on stuff like that. I know he's busy but if you leave a message he'll call you back.

If you know the lever ratio, you can figure it out.


What a royal PITA.

What do the people who made the hydraulic TO bearing say? They ought to know something.