Clutch Woes - Seeking a solution

[jhv48]

What has been previously stated is true. If master and slave are appropriately matched, then it is the leverage of the clutch pedal on the master cylinder. My SPF has three holes on the clutch pedal to move the rod up or down. Moving it up reduces clutch effort but also shortens the stroke of the master cylinder. Moving it one notch down increases both the effort needed to depress the clutch and the length of the stroke..

You need to balance the three parts correctly in order to implement smooth clutch action. Continue your efforts in this area and you will solve the problem.

If you move the mounting point up on the pedal, you might need a larger master cylinder in order to pump enough fluid with the shorter stroke. Like I said, a balancing act.

[stephen low]

Thanks also Murray and Jim

Yes I guess there hadn't been too much science in this change over so it is biting me now, but it sounds like the issue can be overcome - I hope.

There was an evident mis-alignment between the slave and fork actuation but I had been working towards correcting this and it did slightly reduce pressure but nowhere near enough.

Will hopefully work out tomorrow what I need to achieve.

In terms of trying to do some belated maths, what measurements do I need and how do I make the assessment on the hydraulic advantage?

I am assuming length above and below master connection point to clutch pedal, cylinder size of master and slave - though I then don't know what to do with this data, length of clutch fork - should that length be from centre input shaft out to slave connection point? and do I need to know about thrust travel distance?

Feedback on the calculation techniques would be appreciated as I'm always happy to learn.

As I said early the one happy point for now is that McLeod said that a 3/4" master was sufficient for this application so I have one thing correct for sizing but as has been said, where it connects to the pedal is also important.

Anyway I look forward to further feedback.

Cheers

Steve

[muzzza]

Stephen, PM me and I will send thru' a PDF of generic hyd. clutch set-up. Murray

[stephen low]

Thanks Murray

Sent a contact email and look forward to seeing your information.

Cheers

Slo

[Rebel1]

Slowy, My pedal box is not terribly different from yours and I also run a TKO600.

I found two problems. The first with the pedal box and master cylinder alignment with the master cylinder. The push rod when attached to the pedal with a clevis did not align. I had to make a push rod which mounted to the left side of the pedal to get a straighter push.

Secondly, I found that if one used the earlier clutch TOB lever which pivoted from the left hand side of the bell housing (relative to the main shaft) then the pedal was too heavy.

If one uses the later clutch lever which pivots from a ball on the right hand side of the main shaft then there was a heap more leverage and a much lighter pedal.

However, that means the slave has to be mounted to the rear of the lever.

Here is a link to the slave kit which pushes towards the front of the car for use with that type of lever.:
DazeCars, For Sale Page

[stephen low]

Rebel

Thanks for this info.

I know Marty added a heim joint onto one of my pedals at least but I'll review this issue.

As to the lever I ended up with a Dellows housing that allows the fork to exit on the drivers side as you are suggesting and the slave is located in front of the fork and pushing rearwards.

Your description on the alternate location isn't making sense to me unless the fork travels all the way across the housing and is pivoting off the passenger side much as that US product suggests.

Or am I picturing your description incorrectly?

Steve

[Rebel1]

Originally Posted by stephen low

Rebel, Thanks for this info.
Or am I picturing your description incorrectly?
Steve

No you have it correct. The clutch fork exits the bell housing on the left side of the car but travels across to the right hand side of the main shaft and pivots on a ball.

this is the old version:
NOS GENUINE FORD 289 302 V8 CLUTCH FORK XR XT FALCON GT on eBay!

this is the new version:
Google Image Result for http://1.cdn.lib.americanmuscle.com/files/clutch-16.jpg

much greater leverage with the newer version.

[Rebel1]

Originally Posted by stephen low

Rebel

Thanks for this info.
I know Marty added a heim joint onto one of my pedals at least but I'll review this issue.
Steve

I also used a heim joint and a couple of spacers to get the master push rod to align better. I also raised the pivot hole in the pedal ever so slightly so that there was a better alignment through the full travel of the pedal.

[stephen low]

Ok a small update from Saturday's shed efforts.

First discovery was that the slave I'd been supplied by Dellows was only 3/4" so with a 3/4" master I have a 1:1 hydraulic ratio.

Interestingly I discovered as I was trying to find the clutch release point that even at full pedal depression the wheels remained locked. After much gnashing of teeth and of course checking I didn't have the handbrake on, it was looking grim that I had an internal issue.

However on some reflection I realised that this whole assembly has been in place at least three years now and so it struck me that perhaps it might simply be a frozen clutch.

With a couple of helpful shed visitors and a bit of clutch pumping we did indeed free up the clutch with a very large sigh of relief!!

With the clutch free we did discover full clutch pedal depression generated some 40mm movement at the outboard end of the fork that also seems to retard wheel movement and that a target range of travel of 30mm was preferable.

So after some calculations I've a decision as to whether to try and find a 5/8" master or a 7/8" slave.

Finding a slave that will match the current arrangements might be the harder task but I'll explore both options.

Hopefully my next post will be about the successful conclusion of this mini-saga.

Cheers and thanks to all for your advice and help.

Cheers

Steve

[stephen low]

Another small update seeing as I'm not likely to get back to the car until next week now.

I took the easier option in terms of sourcing a master-slave and fitted up a 5/8ths master. With this the pedal pressure has dropped considerably although I'd rate the feel now as firm rather than comfortable.

I need to bleed the system once more as I don't think it was quite right as there is a spongy feel to the clutch and then re-measure throw distances.

A quick check indicated the outboard fork movement had decreased from 40mm to something like 20-25mm so I still may have some wiggle room to reduce this further.

The provider did say there is no simple look up book for slave types but he could do some checking given a bit of time.

I'm inclined to see whether he can source a similar shaped slave as moving from a 3/4 to 7/8ths slave might just do the trick.

So things are better but perhaps not perfect at this time.

Slo

[AC-460]

Slowy
Take your pedal off and drill a hole up 10mm...... this will increase the leverage and make the pedal lighter..... you may need to increase the length of the push rod to get full stroke out of the master..... make sure the piston comes all the way back in the master.... use a syringe to back force bleed....use the syringe and suck the master almost dry .....then force that syringe full with a piece of clear hose back through the bleeder on the slave ....force it through quickly to force air out of high spots

[Rog246]

Originally Posted by AC-460

Slowy
Take your pedal off and drill a hole up 10mm...... this will increase the leverage and make the pedal lighter..... you may need to increase the length of the push rod to get full stroke out of the master..... make sure the piston comes all the way back in the master.... use a syringe to back force bleed....use the syringe and suck the master almost dry .....then force that syringe full with a piece of clear hose back through the bleeder on the slave ....force it through quickly to force air out of high spots

Or change it to an automatic !! LOL

[AC-460]

I had an auto in mine first but changed it to a Manual....Heaps more fun wouldn't go back to an auto

[Rog246]

Ohh come on...........I was actually taking the PUSS !

[stephen low]

Plan is to re-bleed the system and then accurately measure what fork arm travel I am getting.

If I have wiggle room on this to still provide sufficient thrust movement, I'll then go search for a slightly larger slave of a similar design.

I'll go down the revised pedal lever attachment position as a last course.

Cheers

[jhv48]

As I recall, a larger master cylinder takes more effort but pumps more fluid.
A larger slave gets you less travel, not sure about the effort.
Somebody correct me if I'm wrong, but a larger m/c might make the problem worse. If your clutch disengages fine now, and you are getting about an inch of travel at the clutch fork, you don't need any more.

The next adjustment will have to come on the clutch pedal by moving the mounting rod of the master cylinder up about a quarter of an inch.

[stephen low]

Jim

That's right but I've already gone smaller on the master from 3/4 to 5/8th and this decreased my pedal pressure immensely but still not enough.

Increasing the slave to 7/8th from 3/4 will also have the same sort of effect and will further reduce the pedal stiffness.

But I am going to have to check whether I have sufficient fork stroke now to permit some further reduction in this travel if I do change the slave.

Current pedal ratio is 4:1, if I move the contact hole up some 10mm as has been suggested the ratio moves up to 5.2:1. This too would soften the pedal pressure feel.

It's a bit of suck and see now as to which option might get me a good result and I'm likely to check out both ideas.

[AC-460]

These are the pedals I have in mine 6.25 pedal ratio

http://www.summitracing.com/parts/wi...3950/overview/

[besso]

go cabel

[stephen low]

Besso

I could even go a cable clutch but that's what I left behind because of the way the pedals are set up.

If I had a way of hiding the lever-attachment point for the cable to the pedal I'd have probably revisited that idea but below was the initial set up I used and it's just butt-ugly!! nuff said



Anyway a measurement test Friday suggested that I was at the minimum movement limit for the thrust bearing to achieve the 12-13mm clearance as specified by McLeod.

Interestingly during an exercise yesterday to cost a replacement standard clutch assembly, this provider suggested that there need only be 6mm travel at the clutch for release.

I didn't get the chance but it would now be worth my while jacking up the car and seeing practically where the release point is in terms of fork travel.

I could get the slave honed out one size and this would further reduce pedal pressure at the cost of further reduction in hydraulic throw, and I can't without more major work, reposition my master higher up the pedal so that option is out too.

Beyond the $440 for the replacement clutch assembly, I have plenty of time on my hands to do this swap myself, and it may come down to this for ultimate peace of mind.

Cheers