Hey guys, I didn't see a specific thread on this, but please point me in the right direction if I missed it. I'm getting ready to assemble parts for a Hydraulic Master cylinder on the firewall and a Hydraulic TO bearing on the trans and have a Geometry question and then a Volumetric question (I guess that's still geometry). 1. I've seen quite a few factory clutch pedals and they look simple- still swinging in an arc at the pushrod attachment point. How much arc can the Hydraulic MC handle? I assumed it would require more of a straight push in/out and not tolerate much up and down articulation as the attachment to the pedal travels in it's arc. I guess I figured on seeing some crazy articulated pedal gizmo that resulted in a perfectly linear pushrod, but I've never seen that. 2. If I know the Hydraulic TO bearing for my trans wants a 3/4 inch diameter Master Cylinder-how do I make sure the length of stroke doesn't get me in trouble with the expansion of the TO bearing? Will I explode it if I go too far? Do I simply get a measurement and add a pedal stop to avoid over extension? Does the average diaphragm clutch act as a TO bearing stop? For reference, It's a 1960 Falcon with a small block dodge and an a833 4 speed. I have the factory pedal and firewall and hope to use the ford pedal to push a standard racing style clutch master... Thanks in advance -rick
For a master cylinder to work correctly, it needs to be stroked to near maximum stroke. If not, it will give you all sorts of problems. So, stroke is the important consideration, not arc. When I built my Plymouth, I wanted to use the original pedal cluster. Unfortunately, attaching the MC pushrod to the clutch pedal did not give me full stroke. So, I built an "amplifer" bell crank, if you will. It is mounted between the two and gives me full stroke due to unequal arms on the "amplifier". You have to do some engineering or trial and error to come up with the best compromise. As far as the hydraulic throw out bearing, you need to know how many cubic inches of fluid it needs to operate. Then, you select a MC that will deliver that at full stroke. Make your components strong and don't use anything less than 1/4" full diameter fasteners to build your amplifier. Your leg is pretty strong and you are exerting a lot of torque on the shaft and arms of all linkage.
I converted a friend's Nova from an automatic to a six speed manual trans. We changed his pedals out to factory manual 4 speed pedals, and I removed the master and slave cylinders from the '95 Camaro we used as a donor for trans and cylinders. I mounted the master on the firewall and using the same pushrod that connected to the Z bar, I reworked it to a round end that sits inside the master cylinder on the firewall. Then ran the stock hose down to the slave and made a custom fabricated bracket to work the clutch fork. It works just like it did in the donor car, and the angle of the rod from pedal to mater doesn't change enough to hurt anything. He's been driving it for almost a decade of trouble free use.
On the '38 Ford pickup, I adapted a hanging pedal assembly from a '52-'56 Ford car. Used a master and slave from a mid '70s Mazda/Ford Courier pickup. Small block Chevy and T-5 5 speed from and S-10. Fabbed a bracket to mount the slave cylinder to operate the clutch fork. Worked well. Master and slave cylinder need to be the same bore.
I have used this with great success. http://www.partsmike.com/index.php/products/hydcl00ss-hydraulic-clutch-kit-cj-and-universal
I like the slave cylinder pushing on the original throw out bearing fork Daddy did this on his 32 Vicky when I was soilin my diapers I worked in a restoration shop after I retired cause I love old stuff I never installed a hydraulic throwout bearing but several of the guys there did Not sure if it was installation error or what, but more than half of them came back And every 4 or 5 months, another would come back, got tired of pulling transmissions... lol Ricky.
Well, GM, Ford and Mopar install them and warranty them just like any other part. Were your guys using an OEM part or aftermarket? jack vines
Seems I never read about mechanical clutch linkage failures but constantly hear about hydraulic clutch systems failing / leaking ...
Most hydraulic TO bearings include specific instructions on how to prevent over stroking since it's the biggest failure mode. It usually involves jacking up the car and have someone try to rotate a rear tire while someone slowly depresses the clutch pedal just until the tire starts to rotate. You then need to install a mechanical stop on the clutch pedal. I make the stop with an adjustment screw to be able to fine tune the break point. If you use the correct master cylinder and have a pedal stop a hydraulic TO bearing is extremely reliable.
I'm not a big fan of hyd throwout bearings. It is small and tidy, but requires major disassembly if/when issues come up. Bleeding and lines are often as cramped or worse than linkages. That said, I'd attack it by one of the following tactics. I'd find a complete donor setup as @1971BB427 and @38fordpickup pickup did, relying on factory engineers and avoiding math. Using a slave that is external to the bellhousing and acting on the mechanical linkage. This avoids the internal stuff at the cost of space and your chassis/drivetrain mismatch. This is not as popular and requires math and fabrication. Contact an aftermarket seller and make sure you have lots of measurements of the pedal area and the clutch info. Let them do the math and pay for a complete setup and after sale service. If you are hoping that someone has been through exactly what you are doing and has a solution with math equations, part numbers and YMM applications for yard scrounging, I doubt that's going to happen.
Good points, all. I'm not trying to do a junkyard crawl. Most of these answers regarding a matched set are what I was expecting, including a pedal stop. Evidently the arc of the pedal to pushrod attachment point is not so much that people have hurt MCs with it, so i guess it's down to me and some ratio math to make educated choices. I would really like to be external slave cylinder for maintenance reasons, but that does take up a lot of room, and at the rate i'm going, I'll be a week away from dead before I drive it, so i'll let the next guy deal with repairs... -rick
searching "automotive hydraulic clutch pedal ratios" came up with a bunch of little snippets of info, centered around 6:1. This one shows more and explains more. Your concern about arc is not an issue, and it covers it in depth. https://www.mcleodracing.com/blog/how-to-calculate-pedal-ratio-for-hydraulic-linkage/236 EDIT: I didn't check, but if they have this info for the pedal, I'd guess they also have tech info for cylinder sizing and travel.
Thanks! I saw a wildwood universal pedal online that was listed as 7:1, which definitely backs up thay article that the factory mechanical can't be used. I guess I'll need to find out the ratios of a factoy mopar 4 speed car to determine what the 833 needs, then work on the falcon pedal using that method. Thanks again. -rick
Factory Mopar pedal ratio is not what you want, since it's linkage. there is a bellcrank and clutch fork changing ratios. It's on that page. You want what is clutch opening in either hyd inside or outside or outside lever movement if using external. Then you want fluid volume at slave to determine fluid volume at master, and throw of master. Both master and slave can be sized (diameter and travel) to move the clutch properly with the pedal ratio and force.
what i meant was that i'd use the Mcleod info to pretend i'm modifying the mopar vehicle from mechanical to Hyd MS and TO bearing, then apply that required new pedal ratio to the one in my ford. -rick
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