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I recently did a changeover on my '78 from automatic to a M-21. Built a custom motor and installed all kinds of goodies. Then I had health problems that have made it very difficult to use the clutch, which is a dual disk and stiff as hell. Is there a hydraulic assist mechanism that can be installed without taking this thing apart.?
The only vehicles that I'm aware of that have a clutch assist are heavy duty trucks. They are air operated. I know this is subjective and I also know you mentioned you don't want to take anything apart but I'll say this anyhow. I have a McLeod Street Pro which is recommended to 400 HP and a hydraulic setup from Silver Sport Transmissions. The pedal effort is fairly easy.
My friend's truck has a hydaulic fluid assist. It is self contained....it has it's own hydraulic fluid resevoir, eliminating the need for an engine-driven hydaulic pump.
Basically it works like a motorcycle brake...the cylinder mounts to the firewall where the brake pedal can actuate the hydaulic cylinder which pushes the clutch arm.
Check online...the stroke of the hydraulic cylinder is the important part...it needs to have a long enough stroke to fully release the clutch. You can get a decent assist for $100-$200.
One way for passive mechanical advantage is to replace the master with one of smaller diameter. You exchange a longer pedal travel for reduced effort. If you have a 7/8" master, get a 3/4", and so on.
Silver Sport made the conversion kit I used to go from Auto to 4 speed. I talked to them and they have a kit, but it's a different throwout bearing, so it must come apart, and they want more the $800, so there is that. This motor is well north of 500hp, It was the one I always wanted to build, and of course I got sick.
I found something Ecklers offers, but not sure if it's bolt on external. Hydramax master cylinder kit. by American Powertrain. I called them, they haven't got back to me yet.
One way for passive mechanical advantage is to replace the master with one of smaller diameter. You exchange a longer pedal travel for reduced effort. If you have a 7/8" master, get a 3/4", and so on.
Is your new CF image something you may want to share?
My zbar has a couple of different holes and I suppose one could even drill more to change the leverage. OP might want to check his setup, pretty easy change.
1980L-82
I had a stock replacement clutch put in because I did not have time to do it and had to go out of state. That thing would thing would slip if I hammered it. It was ok for milling about but just weak. It was a lot easier to use than the previous monster I had so I did not want to go back to that.....so.....
I installed a Centerforce Dual Friction. Egad that was wonderful. Easy to use, not stiff at all, and it would grab wonderfully. I suggest you look at that before reinventing the wheel. I really liked it. Used it for a couple of decades before I went to a 200-4R.
After some research, it looks like I'm taking this thing apart. The clutch that I have in there is an either its engaged or not type, no feathering. Which would be controlable if I still had that kind of leg strength. Grin and bear it.
Before you start tearing things apart, you might look into the Speed Direct clutch linkage kit.
Numerous of us have installed them, all you need to do is replace the linkage rods to the new spherical rod ends and it is supposed to make a world of difference.
I just installed the kit on my car but haven’t driven it yet.
Ignatz has the kit installed and many others do as well.
The kit is nice, but we have all upgraded some of the components to make it even better.
There have been several threads on the kit and the modifications.
I also posted a recent thread of the install and upgrades.
To me it would be worth the try before you go with a hydraulic clutch set up.
1980L-82
I had a stock replacement clutch put in because I did not have time to do it and had to go out of state. That thing would thing would slip if I hammered it. It was ok for milling about but just weak. It was a lot easier to use than the previous monster I had so I did not want to go back to that.....so.....
I installed a Centerforce Dual Friction. Egad that was wonderful. Easy to use, not stiff at all, and it would grab wonderfully. I suggest you look at that before reinventing the wheel. I really liked it. Used it for a couple of decades before I went to a 200-4R.
Do some research on the Centerforce clutches before you pull the plug on one.
They were the go to clutch years ago, but they had some really poor reviews about 5-6 years ago regarding causing vibrations in the drivetrain.
They may have resolved the issues since then because there hasn’t been much talk about it for the last couple years.
Last edited by OldCarBum; Jan 18, 2026 at 08:34 PM.
You will have to do some research to see if you can make something like this work for you...either that or pull the tranny and install a hydraulic throw out bearing. Ive been using the McLeod versions for years and swear by them
Last edited by Rescue Rogers; Jan 18, 2026 at 04:39 PM.
Hydraulic actuator
