Projects Help With Hydraulic Clutch

Trying to help a friend and now I own this job and need some help.

60’s Valiant with a 360 4speed.
Someone installed a hydraulic clutch release with a willwood master and slave cylinder that pulls on the fork.
The fork has been shortened to accommodate some silly big headers.

it lasted for about 1000miles and then no clutch. Fluid was bypassing the master cylinder so we rebuilt that. The rebuilt master did the same thing the first time we pushed the pedal. We heard a woosh, pedal went to the floor and clutch fork didnt move.

we then installed a new Tilton master cylinder and the pushrod from the pedal bent as soon as we pushed the clutch pedal.

Is it possible this thing has such a heavy clutch that with the short fork the hydraulic system won’t work?

Is there any way to get more mechanical advantage to make this thing work?

should I be looking for another problem with the clutch?

 

Clutch guys will know, but I had a pedal ratio problem when I went with one. You need to research it, but 5:1 seems to stick in my ancient head. Also, found that you have to have like a class 8 type rod to activate it, anything less seemed to bend.

 

I've worked on a few, that's why I hate 'em.
First, was the old MC and the new different brand MC the same bore/displacement? If not, find out what is needed.
Second, divorce the operating system and the controlled system. IE remove the slave and make sure the pedal and MC operate the slave the full expected stroke the same each time and fully releases.
Then using a big pry bar, make sure the clutch fork can operate the clutch properly.
Third, somebody went in and cut things. Make sure that is what was supposed to be done or if all the mods need to be replaced.

 

"The fork has been shortened to accommodate some silly big headers."

Did you lose mechanical advantage when this was done? Assuming your MC and your slave were the same bore, if you generated 1000 psi with the MC, the slave would see 1000. If the fork shortening cost you, say 30%, the pressure would increase to 1300 psi. You may have reached a point that is too high for the seals in the hydraulic system. It all was engineered to work together. Now, it has to be reengineered. Good luck!

 

Always easier said than done. But
The geometry of the linkage was determined by need. The 'chop job' is causing to much load.
Strain. The exhaust needs to honor the space.
rockable just beat me

 

Thanks for confirming what I thought.

cutting the fork reduced Mechanical advantage by shortening the lever.

The new master is the same bore as the old one.
With the Slave disconnected it moves through the full range.

the only wild card is the clutch and pressure plate.
With a 30” pry bar against the throw out bearing I couldn’t get the clutch to release.

I hate fixing other peoples hack jobs

 

60s valiant + V8 headers. You have stumbled into the danger zone.
Hacked, then pushed off for others to fix. You have stumbled into the time and money pit.

Explain to your friend that this should have been planned for, the options discussed and the job isn't going to satisfy him until he understands that early A bodys have tight bays, leading to all sorts of exhaust/steering/starter or wheel clearance (fenderwell) issues. Explain that this is going to require compromise and he's got to choose what path before any further work is done. Price out the work and get his approval before doing any more.

I'd suggest starting here
https://www.forabodiesonly.com/mopar/forums/small-block-mopar-engine.52/

 

Can't you eliminate the fork and linkage and use a hydraulic release bearing ?

 

How is the pedal pressure? Mine I had moved the rod lower on the pedal arm, no good. The car was not driveable. I put it back stock and moved the clutch master up higher on my mounting plate.

Mine is a push type and I use a stock length fork. The short fork thing has got to go.

 

It is also possible that the fork and throwout bearing has somehow jammed inside the bell housing. Is there an inspection plate that can be removed to take a look?

 

This is probably the best idea, however the current set up worked for a while and my friend is extremely cheap and neither of us wants to pull the transmission out lol

 

The pedal has lots of pressure, in fact too much because the pedal is breaking things.

 

I pulled the inspection cover and the fork is installed correctly and the throw out bearing moves freely.

 

The modified shorter fork = higher force; but less stroke to operate clutch.

A larger bore slave cylinder will exert more force and with less stroke required may still match the master cylinder fluid displacement and do the job.

 

The pedal ratio has been queried earlier but not responded to. Whilst it's possibly OK it would be good to eliminate it from the enquiry!

How much was lopped off the arm?
I've no idea whether a 30" prybar would be able to operate a clutch and I'm not seeing how hydraulic pressure in psi converts to ft lbs, so can't compute / compare.

I like my hydraulic throwout out bearing, but accept many swear at them. I've not had any issues, yet, though!

Chris

 

One other thing to check that no one has mentioned.
Is the push/pull rod in straight alignment? Or do they engage at an angle?
Good alignment is when the push or pull rod is straight in line with the bore at half travel.
Wilwood makes good stuff. The master and slave in my OT drag racer have been in operation for over 20 years. I built all my own bracketry, paying close attention to alignment.

 

I guess that depends on where you pivot the bar (how far from the end). If you pivot an inch from the end, then you get almost 30 times the force. If you pivot two inches from the end, only 15 times the force. Etc.

ft lbs might be a way to measure torque, but here we're dealing with force...and psi converts to pounds by multiplying by the area of the bore. A 3/4" bore slave cylinder has a little less than 1/2 square inch of bore area, so if you apply 1000 psi (fluid) to it, you get 442 lbs force out the pushrod.

I have no idea how to apply any of this to the existing situation. No pictures, etc.

 

Let's see how many folks can find different ways to say the same thing & how long they'll keep doing it..

 

Yeah, most online stuff only cover parts of the system, not the whole thing because they don't want to shove a ton of math into it and there are fairly wide ranges at each point along the path.
Pedal ratio is mentioned as about 5:1, but there isn't a standard linkage ratio across all the different systems. Same with the leverage at the clutch fork, but I'd guess they are fairly close. NOT interchangeable, though. Some hyd systems use a fork, some are direct acting. Then the amount of travel for each clutch from fully released (engaged) with free play to fully open (disengaged) with gap are different but probably all within a fairly narrow range, but different amount of force.
Some designs also apply more engagement when spinning (centrifugal).
Then you get into multidisc, different materials and linkage and hyd release.
Since each all operate with a limited force and throw of leg power, they have a fairly narrow starting force, but how this is used is going to be different and what works for one system is not going to work for something else, so there isn't a basic rule of thumb due to all the variations.
https://www.theengineerspost.com/9-different-types-of-clutches/

 

I’m confident the pedal ratio is not the issue.
When the clutch worked it was very easy to push, easier than a bone stock 80’s economy car according to the owner.

But the willwood master couldn’t handle the pressure needed to move the short fork, so it’s seals failed.
I do t know how much was removed from the fork, probably about 3” of 16”, but that’s just a guess.


the Tilton master will operate the clutch but the rod between the pedal and piston keep bending. The pedal is not in alignment with the piston so the rod is an s shape- forward from the pedal, 45° left then straight in to the piston.
the first rod was 3/8 and it bent from 45° to 90° where the s bend was when we pushed the pedal.
I made a reinforced rod with triangular gussets and it bent at the 3/8 straight part where it pushes the piston. I can’t make the 3/8 straight part any stronger or it won’t fit to push the piston.

 

then this is the problem. Pictures would sure help us see stuff like this, without waiting for you to get around to mentioning it....and might let us suggest how to fix it.

 

^^^^^ On this issue but at the other end of things. I had a bellhousing that had a different clocked exit for the clutch fork in relation to the bellcrank. Not good. Either up top, any where between or below. Things need to be squared up to work correctly.

 

You have to limit the pedal travel also or you will over extend the MC . I am working with a Wilwood now and it can only travel 1.12" and then it will leak.

 

I would look into a mechanical setup.

https://www.brewersperformance.com/

 

The car isn’t at my house and I didn’t take any pics yesterday when we were working on it. I agree that pictures would help.

It would also have helped if the last guy to work on this hadn’t hacked it up adding a homemade hydraulic setup instead of fixing the stock mechanical setup like they should have.

Do you have any suggestions on how to align the pedal arm and master cylinder?

the master is about 2” to the left of the pedal arm, the pedal arm is directly behind the brake master cylinder so I can’t move the clutch master cylinder to line up with the pedal arm. I really don’t want to get in to modifying the brakes to make the clutch work.

I’m trying to imagine a bracket that would attach to the side of the pedal arm to move the pushrod 2” to the left, but don’t have that much imagination.

 

A spacer on the pedal could get you there. Would need to be very stout, probably 1" round bar drilled to suit, and probably welded to the pedal. But I'm thinking that if 3/8" rod, gusseted, couldn't cope other things could break or bend too. To get the rod to bend must have taken some severe effort, no? And the endgame has to be an acceptable light clutch, right?

How is the rod attached to the pedal? A clevis? Switching to a heim joint ro the side of the pedal (w spacer?) will get you there / closer. Thinking about it, with a heim the answer is obvious, so I guess you have a clevis, which might explain your visualisation problem!

Pics of mine, brake but you get the idea.



Chris

 

So let’s get all the facts together:

1) At the pedal end, the pedal is 2” offset to the master cylinder, so it has an S shaped actuating rod.

2) At the clutch end, the fork has been shortened by a decent amount and the slave is not inline either?

so you’re asking for more force in a less optimal angle.

You need to follow the advice above and tell your pal he’s going to have to pony up, there is no cheap way to sort this.

Literally 1000’s of folks have put those motors into that chassis/body, there must either be an off the shelf solution or some documented method to doing the swap.

I hate to utter the names here but those Roadkill and Hot Rod Garage shows seemed to be putting big block Mopars in A body’s every other episode.

 

BBM's fit in the late A-Bodies much easier than the early ones.

 

Fair enough, not hugely educated in that dept. Thanks!

 

There's your answer. Aside from the excessive force to move it, it will likely not move the fork enough to release the clutch.

Mine needed about 1" of linear travel at the fork. My slave was rated at a 1.25" stroke. The slave is 7/8" bore, the master bore is 3/4" which I was told is a good combination.

I used heim joints where I could. It is essential to eliminate as much slop as possible.