Second of Two Dumb Questions today Was out working on the '51 - and I've nearly got the clutch pedal dialed in. (I'll post pics of the bracket I made in the next couple of days). It's a firewall mounted hanging setup. I've noticed, when depressing the clutch, it starts easy for the first 1/4, then gets' very very stiff, then easy again for the last 1/4. Here's a nice chart for ya. When releasing it, it's easy then so stiff it pushes back at you. So... I'm trying to troubleshoot last night and I realized that I've never owned a car with a mechanical clutch linkage. They've all been hydraulic. What's it SUPPOSED to feel like? Is it supposed to be consistent all the way down, or is there supposed to be hard/soft spots in the travel? What would make it feel like that? My linkage is homemade - but I'm certain it's not binding because if I pull the clutch rod (block side) off the z-bar the pedal moves freely.
Breaking over the pivot point on the Z bar. Once it reaches a certain point the angle changes and it gets easier to depress.
I'm interested too. I have a 36 pickup w/327-4speed, Centerforce clutch/pplate, Z-bar....same deal. Pedal moves easy, then hard, then easy after the pressure plate collapses to release the disc.
Some factory cars used an "over-center" spring to fix that problem. The spring gets "loaded" as you go through the easy part, then in the way the spring is mounted, it then goes over-center and "unloads" to help get past the stiff part of the pressure plate resistance. One car that comes to mind, that has hanging pedals with that setup is late 60s Dodge Dart. Don't know if you can find an online pic or parts diagram, to help figure one out for your car. Edit, those Darts had the spring up at the hanging pedals. But, an Olds from the 1950s has that over-center spring mounted to a lever on the bellcrank/Z-bar.
That's very interesting. So you're saying it's sort of binding on the z-bar? Is this a geometry issue?
I've had many cars with mechanical linkage through the years. Some pushed in easy, some hard, but they all pushed the same throughout the stroke. Either easy all the way or hard all the way. I'm currently setting up a 57 Chevy with everything original except motor mounts, bellhousing and clutch kit. So far I've destroyed two throwout bearings and you need a 350# gorilla to push in the clutch. Tomorrow I am pulling out the RAM clutch kit and installing an OEM unit from NAPA, to see if the pressure plate force is to high on the RAM unit. Also trying to revise the linkage angle from the z-bar to the bellhousing so it will have a straighter push, it currently pushes down on the clutch arm,popping the arm off the pivot ball and.... you get the idea...
Clutch should have even pressure throughout the stroke so my guess would be to play with the length of the arms on the Z bar and rod back to the release arm until the ratios are correct. Best clutch I can remember was a '63 Chevy with 327 SBC and Muncie 4 speed. It was soft and easy but engaged just off the floor and never slipped.
At what point on the chart does the clutch disengage? If you don't need full pedal you could adjust the bell crank arms shorter to give you more leverage. You could also move the shaft on the clutch pedal up toward the clutch arm pivot point for the same effect. If you need a full pedal to disengage the clutch you may be limited to trying to fit in a helper spring or trying a different clutch.
Geometry its all geometry Lever lengths and pivot points. Some place in the linkage you have opposing pivots getting closer to each other. That would be at the highest part of the graph.
My left knee says that chart is right on. I've owned a couple of knee shake rigs and have driven all too many that you never knew when they would engage or when your knee would quit shaking.
I would say you need one more inch of leverage somewhere in the system. If the bottom of the bell housing comes off, try adjusting the clutch so when the pedal is down all the way, there is .030 to .040 clearance between the disc and the flywheel or cover. Then see how it acts.
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