C3 Hydraulic Clutch [PICS]

Here is another mod made cheap by using OEM parts, a little time and fabrication. The only major tools you should need for this are a Sawzall (or any other metal cutting tool), welder (I use a 120 volt MIG), a grinder and a hand drill (a drill press is always nicer). It is fairly easy to do and well worth the time it takes to fabricate to save a couple hundred bucks. There are two different types of hydraulic clutch styles. One uses a hydraulic throwout bearing to disengage the clutch, and does not use a clutch fork/pivot ball. The second style uses a slave cylinder which takes the place of the Z-bar linkage and hydraulically actuates the clutch fork. Both styles have their own pros and cons. Doing some research showed that going with the slave cylinder style would be cheaper and easier for me. The slave cylinder style does not require removal of the transmission, and is significantly cheaper than a hydraulic throwout bearing.
For those of you with stiffer clutches, going to a hydraulic clutch may help to reduce pedal pressure by eliminating the friction created by the pressures put on the Z-bar, depending on its condition. In addition to the easier pedal pressure, this particular hydraulic clutch setup auto-adjusts for clutch wear too. Besides the mechanical positives of a hydraulic clutch, it looks cleaner and clears up the engine bay a little too by getting rid of the Z-bar. The nice thing about this mod is that you do not need to take your car off the road for days at a time. The Z-bar comes out with a spring pin, a bolt on the frame bracket, and a bolt on the clutch fork. It takes all of 10 minutes to take out/put on the Z-bar assembly, so when you are done with mock-up for the day, it can all go back together quickly and easily.

I began by buying a clutch master cylinder and slave cylinder from a 1986 Chevy C30 pickup. I’m not sure if it matters, but I chose the 350/5.7 engine. Rock Auto seems to have the best prices at $33.79 for the master cylinder, and $51.79 for the slave cylinder.

Here is the stock clutch setup:
This shows the clutch pedal rod and part of the Z-bar assembly.


Here is the master cylinder made by Wagner. Part number CM110273.


And here is the slave cylinder also made by Wagner. Part number SC103483.


Next is the master cylinder reservoir. I read that a bunch of people use reservoirs from Hondas, and C-4 vettes. I couldn’t find any of these on Rock Auto, AutoZone, Ebay, etc… My friends all have sport bikes and I noticed that the front brake reservoir would be a perfect candidate for the master cylinder reservoir. It has a bolt-on style mount and the proper size hose barb on the bottom. This one is from a 2003 Yamaha R1/R6. It was about $30 from my local motorcycle repair shop.





With the Z-bar and clutch pedal rod removed, I marked and drilled two mounting holes in the firewall. There is already a piece of steel behind the fiberglass which makes reinforcing the firewall unnecessary.


Here are the holes from the inside of the firewall with the master cylinder in place:


Here is the master cylinder mocked up in place.




Here is where the stock clutch rod attaches to the pedal under the dash.


This is the only mod you will need to do to the master. The rod is too long by about 1 ¾ inches. It needs to be shortened and then threaded to fit.





I took the other end of the rod that I cut off and threaded it, and welded in a sleeve to reduce the diameter to the size of the pin on the clutch pedal. Here it is in place, mounted on the clutch pedal:


Next, I fabricated a small bracket for the reservoir out of sheet metal. It mounts to the power brake booster bolts on the firewall and the brake master cylinder stud. This position may not work if you have a vacuum brake booster. Anywhere else is fine as long as it is above the master cylinder. The hose size is ¼ inner diameter.

Next I fabricated a bracket to mount the slave. This is probably the most difficult part of this job (besides contouring your body to fit under the dash) I made a bracket out of some 1/8 inch steel I had. My bracket mounts using a bolt that holds the bellhousing to the block, and the extra provision for a pivot ball on the bellhousing. Here is my bracket mocked up in place (the carriage bolt is just for mock up purposes).


And with the slave mounted:


Painted:


Here is the slave mounted on the bracket with the hard-line mounted. The slave and master both use a 12mm bubble flare. NAPA sells the fitting to convert from the 12mm bubble to a 3/16 brake line and double flare. The reason I used a hard-line was because I did not want to have a rubber hose that close to the headers.


I ended up going with a stainless braided line. I had this made at a hydraulic line shop for $18. It is important to have some kind of flex line so you do not fatigue a hard-line from the constant movement of the engine.


In the final position:


I used the same 12mm to 3/16 brake line fitting for the master cylinder and ran a simple line down the firewall to the flex line coming off the slave cylinder.

The slave cylinder comes with a steel rod that actuates a ball and cup style clutch fork, as seen here:


Being that everything is metric on these parts, the rod is too small in diameter for a 3/8 thread, so I welded the threads from a 3/8 grade 8 bolt to the end of the rod. Then I made another threaded piece to mount to the clutch fork.




The last part of the project was to make a clutch pedal stop. Depending on how short you made the master cylinder rod, you will have to make some kind of clutch pedal stop so you do not bottom out the master cylinder. I made a simple plate with a nut welded on it and riveted it to the floor. I then used a carriage bolt and a lock nut to set and secure my depressed clutch pedal height.


My previous clutch z-bar setup was “over” disengaging my clutch, and now that the pedal travel is properly set, I know that I can push the clutch pedal in only about 2/3 of what I was before, and still completely disengage the clutch. Because of this, and the fact that my clutch pedal sits a bit higher at rest, my clutch safety switch does not activate, and a longer rod has to be made to make it fully activate the switch. To test if your clutch is fully disengaging, start the car with the clutch in, and the trans in neutral. Let the engine idle for a few seconds, and slowly try to put the car into reverse (assuming you have a non-synchronized reverse gear- muncies and the tremec TKO’s are not synchronized). It should go into gear smoothly and you should not be able to hear or feel any grinding. If it does not, you need to either adjust your pedal stop (if the master cylinder allows for more movement) or adjust the slave cylinder’s resting position on the clutch fork.

Back to math class for a minute… this master and slave cylinder combo gives minimal slave travel to push the fork in. The master cylinder uses an 11/16th inch bore. So we do pi X radius^2 and come up with 1.49 cubic inches of volume at 1 inch. The slave cylinder has a 13/16th inch bore, which gives it a volume of 2.07 cubic inches. This means that for every inch that the master cylinder moves, the slave cylinder will move .72 inches. I was able to get a max travel of 1.5 inches out of my master cylinder. Other people have reported less, so just double check it yourself. At 1.5 inches of travel at the master cylinder, the slave cylinder will move just over 1 inch. This should be just enough movement to disengage most clutches. It is still important to check for full disengagement and that there is no pressure on the throwout bearing when the clutch pedal is in the neutral position though.

Overall, I have to say it is a pretty straight forward job to complete. I have driven the car for a few days now with the new setup and it is nice and smooth. I was really hoping for a little less pedal pressure, but my z-bar was in good enough condition where it did not add any unnecessary resistance. My slave bracket has a tiny bit of flex in it, so I will end up taking it out and weld in another brace or two. Otherwise, it works great and has a more modern, smooth feel when engaging and disengaging the clutch.

Total cost:
Master cylinder……………………………..…$34
Slave cylinder…………………………..………$52
Braided flex line……………………………….$18
Nuts, bolts, hard-line, and fittings…..~$15
…………………………………………………………$119

-Chris

Nice work and writeup!

BBShark said:

Nice work and writeup!

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Yes, for sure,.......:bump:

One thing to add, if you have a vacuum booster, it's VERY tight where that plastic plug goes into the master cylinder. I ended up modifying mine for a steel line to have enough clearance. What a PITA.

I may just have to copy that bracket to get rid of the Z bar on a 4 speed.

Great job and an awesome write-up :thumbs"

How did this end up working out? I know you had some problems after this post. Any further info?

BBShark said:

How did this end up working out? I know you had some problems after this post. Any further info?

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If you really want to know, I have been driving my car for about a 2 weeks now with the z-bar setup. :banghead: I really had no reason to do this mod other than hoping that I would get a little bit less pedal pressure because I thought my z-bar was a little rough. Plus, I like to fabricate and "mod" my vette.
Anyway, heres what happened- It worked great for about a day or two, then I started having trouble putting the car into gear. I saw a little puddle on the nipple where the reservoir hose goes into the master. So, I spend $30 and bought another one. Must have been just some fluid I spilled, because I went to start up the car, drove it in the backyard- all was good. Took it out on the street for a 2 minute test drive, and I was ramming the trans into gear again. Bled it some more, same situation. I noticed the slave was leaking fluid out of the boot. I determined that the seal on the cylinder itself had blown out because I did not have it completely perpendicular to the clutch fork, and I must have killed it because of that. In addition to that, my clutch had too much pressure for the bracket that I made and it was flexing more than I would have liked.
So, right now all the parts and brackets are sitting in a box in my garage waiting for me to buy a new slave, reinforce the bracket, and come up with a good reason why I need a hydraulic clutch.
Most of all, I went against the first and best rule of modding a car Keep It Simple Stupid.
If anyone is still looking to do the hydraulic clutch- the Duralast master cylinder uses a thicker rod than the Wagner one. Its just not painted.
I may bring it back once I buy my clutch/flywheel/trans and install them. (18lb flywheel, centerforce DFX and richmond rod 6 speed BTW :harhar: )

One of the hardest parts of installing a hydraulic clutch setup is to make a bracket that can handle the stress of the slave cylinder. Alot of people might not think it, but there is alot of force being applied OVER and OVER and OVER. It takes a toll if the bracket isnt insanely STRONG!!!!

When I did my t56 swap the slave cylinder mounting bracket is already intergrated onto the bellhousing from factory. Eliminating having to make a bracket.

I used the same master cylinder that VETTE427SBC has in his pictures


In my personal opinion the slave cylinder blew out from 1 of 3 reasons. I highly doubt that it blew out from it not being perfectly perpindicular to the clutch fork.

Possible reason 1. VETTE427SBC wrote and I qoute "Being that everything is metric on these parts, the rod is too small in diameter for a 3/8 thread, so I welded the threads from a 3/8 grade 8 bolt to the end of the rod. Then I made another threaded piece to mount to the clutch fork. "

If he welded without removing the rod from the slave cylinder. It is quite possible he heated up the slave cylinder causing premature failure.

Possible reason 2. Having 1 1/2" of master cylinder travel is alot!!!! I would bet that the extra travel that he has allowed caused too much pressure and caused the slave to blow out on him.

I am using the same master cylinder as him and I only have 15/16" travel. I didnt use any fancy math or anything like that.
I called american touring specialties AKA http://www.t56kit.com/
They told me how much travel is needed. If anyone would know it would be them. They have more experience installing hydraulic cluthces than I ever will.

http://www.t56kit.com/services/
This might greatly help vett427sbc to solve his bracket problem.

Possible reason 3. The fact that his bracket that he made to mount the slave cylinder keeps moving and is not solid makes it very possible that the movement is causing the slave cylinder to fail. But I doubt it.

I am not an expert in NO WAY, I am just adding my thoughts on the thread. I hope that the information I post will help any future attempts on modding your vette!!

I did not weld with the rod in the slave, and did not overthrow it either. it ended up being that when the clutch was depressed, the bracket flexed and eventually blew out the seal on the piston in the slave from having too much lateral pressure on it

Well that was my possible reason #3..... your bracket had to move alot to cause that.

How much would you think it was moving?

Is your setup all fixed and the project finished? Your pics really helped this thread alot.

jsssgrl1209 said:

Well that was my possible reason #3..... your bracket had to move alot to cause that.

How much would you think it was moving?

Is your setup all fixed and the project finished? Your pics really helped this thread alot.

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It moved a little, but that little bit is too much for something like that IMO. Like you said, with all the force that is put on that bracket and the constant movement from use, the metal will fatigue too easily.

Unfortunately, I am still running my old Z-bar. I just never found the time to go back and re-design that bracket.

My attempts at a bracket

Years ago I attemepted to make a bracket to use a hydraulic clutch in an old camaro I had.

All I will say is My Bracket FAILED. I was young and didnt quite have the fabrication skills I have now, so it was a good learning experience.

I know this is an old thread, but it was so well written I was wondering if you ever worked the bugs out.

one of the biggest mistake people make with hydraulic slave cylinders is locating the push rod in the same place as the push rod of the Z-bar. The problem is you were bottoming the master to get it to disengage. You need to relocated your slave push rod 4/5 of the distance from the centerline... something like 1 1/2" towards the center of the motor.

A second problem is you really have to be careful with the angle on the slave - anything too much and it will side-load that steel rod in the aluminum container (with predictable results)

a third problem, and one that might keep you in the Z-bar business is that hydraulic clutches are linear in pressure - meaning, there isn't that spot you have on a z-bar where you are just about ready to disengage the clutch, most people tend to let the clutch slip too much if they go hydro because where that 'sweet spot' is on a hydraulic clutch allows the clutch to slip..... I'd stay with the z-bar and swap in a few self-lubricating heim joints...

setting up a hydraulic clutch is an unmitigated bitch ('scuse my english)... on my C3, it took 4 set ups before I got it to almost as good as a z-bar.... and the guy who bought it from me burned the new clutch out and ate a few synchros because he can't shift.... he was told, oh well.

I did get it sorted out... sort of...
I ended up with a T56 and a hydraulic throwout bearing actuated by the master cylinder setup that I used in the original post. It worked beautifully and reliably. The master was never overthrown and gave (car is apart now) me many miles of trouble-free hard driving

vette427sbc said:

I did get it sorted out... sort of...
I ended up with a T56 and a hydraulic throwout bearing actuated by the master cylinder setup that I used in the original post. It worked beautifully and reliably. The master was never overthrown and gave (car is apart now) me many miles of trouble-free hard driving

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Just curious, any updates on the rear suspension?