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Clutch Pedal Staying on the Floor

68stang289

68stang289

Member
Hopefully someone can help diagnose the latest issue. :g_beer

I purchased the correct upper and lower springs for a 70 428 setup from Mansfield (Bill is absolutely awesome and a wealth of knowledge in case anyone ever needs big block parts) and have installed those. The upper spring is attached at one end to the little prong on the firewall below the master and at the other end to the notch in the z-bar. The lower spring is attached at one end to the clutch fork and at the other end to the z-bar. I pulled the resto book that I have that shows the breakdown for a 70 car and I didn't see any additional clutch linkage springs needed (I know previous 4 speeds I've owned have used a return spring from the clutch fork to somewhere on the frame, but I didn't see one here). However, when I push the clutch in, the clutch pedal stays on the floor. You can feel the spring on the clutch pedal working once it get's past "center mass" either going down or coming back up.

I know the PO switched the car from a C6 to a 4 speed Toploader, but I have no idea what or where the clutch pedal and bracketry came from. I do know there is a difference between the 69 and 70 clutch/brake pedal assemblies, but could that potentially be causing my problem if he put a 69 or earlier assembly in the car? The setup the PO had when I purchased the car was a homemade frame mount pivot, modified 65/66 upper clutch rod, 351 z-bar, 65/66 style lower clutch rod and a random assortment of springs. I have since gone through and put together all the correct pieces for the setup.
 
Do you have the assist spring that is mounted on the pedal assembly? I thought I read years ago if you have the original style borg and beck 3 finger clutch that you want the clutch assist spring installed, but if converted over to a diaphram clutch, then I think you are supposed to remove the spring.

If memory serves me right, the diaphram clutch gets easier the further you press the pedal, the borg and beck has stiffer springs that requireds a lot of effort to fully disengaged the clutch which is why the clutch assist spring is there. Since the borg and beck has more spring pressure it can overcome the clutch assist spring and return the pedal, but with a diaphram clutch, the pressure plate might not have enough pressure built up to get the pedal back to the nuetral point and then return to its normal position.
 
I also believe that is correct. Using a diaphram clutch, I am using only 1 spring and it's the one at the bottom of the Zbar.
 
Man that damn spring almost took my finger off once. I don't like that spring!!!

I run a regular clutch with all springs installed.
 
Thanks for the info guys! I'm going to pull the inspection cover on the trans and see what kind of clutch is in there. Hopefully this solves my issue.
 
I pulled the inspection cover and I am running the Borg and Beck style 3 finger clutch. I could have swore it was converted over to a diaphragm style clutch, but apparently I was wrong. While I was under there I started playing with the adjustment to see if maybe that was my issue. After looking at my reference book I noticed that the clutch fork was different than they were showing for FE cars. I show this as being the clutch fork I should be using...
08-04.JPG


I've attached a few pictures of the fork currently in the car. Sorry for the crappy quality - I was using my cell phone to take the pictures. It appears to be the early 67 390GT style fork.
 
It appears the only thing different from the 67 FE setup to the 70 FE setup is the upper clutch spring. The 67 style seems to be much heavier duty than the 70 style. Could this be causing the issue given the use of the early 67 FE style clutch fork?
 
"Fast68back" said:
Do you have the spring on the top of the pedal assembly?
Click to expand...

Yes, I do. I thought with the Borg and Beck 3 finger style clutch that you needed the extra assistance the spring offered though?
 
The various springs under the hood are there primarily to keep the bearing from riding on the clutch fingers, not to raise the clutch pedal up off the floor. The over-the-top spring under the dash is what is required for the 3 finger clutch assemblies. It may be that the spring you are using isn't sufficiently strong (wrong model year?) to do its job.
 
"Midlife" said:
The various springs under the hood are there primarily to keep the bearing from riding on the clutch fingers, not to raise the clutch pedal up off the floor. The over-the-top spring under the dash is what is required for the 3 finger clutch assemblies. It may be that the spring you are using isn't sufficiently strong (wrong model year?) to do its job.
Click to expand...

Once you get over the "neutral point" (for lack of a better phrase) the clutch pedal snaps down to the floor or back to the top resting position, which I believe is what it is supposed to do, correct?
 
Are you sure the clutch fork / throw-out bearing are actuating the pressure plate? It's the pressure plate that should be pushing the linkage back to the normal position, or at least past the "nuetral" point on the pedal. Other than that all's I can think of is the pedal spring is too strong, or you have a weak pressure plate, or perhaps theres some binding somewhere.
 
"stangg" said:
Are you sure the clutch fork / throw-out bearing are actuating the pressure plate? It's the pressure plate that should be pushing the linkage back to the normal position, or at least past the "nuetral" point on the pedal. Other than that all's I can think of is the pedal spring is too strong, or you have a weak pressure plate, or perhaps theres some binding somewhere.
Click to expand...

I'm thinking now that maybe the different clutch fork is changing the angle or amount of pivot and not allowing the clutch to engage the pressure plate enough to push the linkage back to the normal position. I also just noticed when I adjust the lower clutch rod out as far as I can, that the clutch fork is hitting the H-pipe when engaged. I'm going to pull off the H-pipe and adjust the lower clutch rod out as far as I can and see if that gives me the spring back I need in the clutch pedal.
 
Another thing to look into is the pivot ball that the clutch fork rides on. I don't know about this specific application, but sometimes there are different length pivots. If too short, the fork might bottoms out before engaging the pressure plate. Just something else to consider if the clutch fork doesn't seem to line up right.
 
"stangg" said:
Another thing to look into is the pivot ball that the clutch fork rides on. I don't know about this specific application, but sometimes there are different length pivots. If too short, the fork might bottoms out before engaging the pressure plate. Just something else to consider if the clutch fork doesn't seem to line up right.
Click to expand...

I have verified I have a correct original FE frame side pivot mount (it is slightly different than the small block version) and a new block side pivot mount which was either NOS or a refurb'd original. I'm running new pivot balls and felts as well so everything should be nice, smooth and tight in there. I am, however, running a repop'd z-bar, so it is possible that there is some binding in the repop'd z-bar. I'm going to have someone operate the clutch this evening and watch everything to check to see if there is any binding anywhere.
 
The pivot I was referring too is the one inside the bellhousing. If too short, the end would move rearward (closer to your H pipe), a longer one would move the end more forward thus giving you more stroke at the pressure plate before bottoming out. They do sell adjustable pivots but I'm not sure which one would work for you... here's one possibilty.
http://www.summitracing.com/parts/lak-15501/overview/make/ford
 
I confess that I errored big time. I somehow modified one of 68stang289's recent replies instead of quoting it. I feel like crap and I'm very sorry. I have thus deleted my modification of it and pray for forgiveness for making such a stupid mistake.

Craig
 
"cmayna" said:
I confess that I errored big time. I somehow modified one of 68stang289's recent replies instead of quoting it. I feel like crap and I'm very sorry. I have thus deleted my modification of it and pray for forgiveness for making such a stupid mistake.

Craig
Click to expand...

Geez, what kind of rinky dink operation are you guys running here!? :sarc

I kid, I kid. No big deal Craig!

For those of you still following my endless stream of stupid questions, I ended up adjusting out the lower clutch rod to where it should be, and then tried the clutch. The clutch fork was hitting the H-pipe and preventing the movement completely. So I ended up removing the H-pipe and reassembling the lower clutch rod and spring. I adjusted it out to where it should be and tried and the pedal came back up to where it normally should be. So the problem ended up being that the H-pipe was not allowing the throwout bearing to engage the pressure plate enough to give it the pressure to "bounce back".

This ended up opening up a whole new can of worms though. The early 67 390GT clutch fork that is on the car is 12 3/8" long, whereas the original for a 428 was only 12" long. From what I can tell from pictures as well, it looks like the 68/69 390 GT/428 style clutch forks have a bigger curve towards the front of the car and a slash clearance cut on the outside of the hole for the lower clutch rod adapter to pass through. When you couple that with running a 2 1/2" exhaust, that leaves roughly 1/2" or so of extra clearance that the factory setup has over my current setup. It also now makes sense how the PO was running the smaller 1 1/16" input shaft Toploader on the car as the 390 GT style clutch forks use the small throwout bearing. The down side is to return it to stock so I can use the 70 428 style clutch fork, I would need to buy a 1 3/8" input shaft, new clutch fork, new throwout bearing and the bigger clutch, which is $500-750 that I just don't have to spend on the car right now.
 
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