zwede

I hooked up my hydraulic clutch (85 pickup master cylinder, novak slave, modified novak bracket). I'm using the stock fork. I bled the system by removing the slave and working the pushrod in/out until I saw no bubbles in the reservoir. I then mounted it, pushed the clutch in and opened the bleeder on the slave.

The problem is I'm not sure the clutch is disengaging. I pushed the pedal down and locked it with a piece of wood to the steering wheel. I put the tranny in 4th gear and was able to turn the output yoke by hand, although it didn't spin freely.

So does this mean the clutch is disengaging properly? Because the pedal is soooo easy to depress. not even half the effort compared to before.

Durango_Boy

The difference in effort is because you now have hydraulic assist where before you did not. It will be like butter compared to how it used to be.

I would think if you can feel it's not disengaging properly, then I would spend a little time adjusting anything that makes a difference. Also, try putting it in gear, and checking the wheels. Then, hold the pedal down with a stick while it's in gear, and try spinning the wheels. If it feels like it's not disengaging, then something could be off.

Chuck Harmon

Zwede,

Wow, I just posted over in the ZO6 forum about how much I miss the mechanical linkage of my 69. Hydraulic clutch systems have a great deal of promise, but I haven't found much, if any advantage, over what I had on my L88. Quite frankly, if I could have a fully mechanical linkage using heim joints I would jump on it in a New York minute!

The hydraulic setup should be smoother, but mine has been less than precise in real driving. Sometimes there is slop in the pedal travel, sometimes it is just fine. I hate it!

The feel of a factory L88 mechanical clutch is a bit crude, a metal on metal feeling compared to a hydraulic system. If you were to use heim joints on the ends I don't think you would feel that way about a mechanical linkage. Again, I miss the mechanical linkage. But I don't think there is room to permit an alternative for me with the ZO6.

Chuck

zwede

Chuck: I had heim joints at all 4 pivot points (the speed direct system) and the pedal was a bear. Way to stiff for daily driving. If the new hydraulic system is really disengaging I think I will be more than happy with it. The effort is so much less.

Chuck Harmon

Zwede,

The less effort is simply due to the mechanical advantage. If you were to lengthen the arm on the upper bar of the bell crank under the hood you would get the same leverage. It simply comes down to the length of the pedal travel. You will not get any more leverage from the hydraulic clutch if the effective pedal travel (point of clutch engagement and disengagement) is the same as a mechanical one. All you are doing is going from a 3/8's ratchet to a 1/2 ratchet. You just need a bit more room to swing the handle on the wrench.

I tried a McLeod hydraulic master cylinder. Much higher pedal effort, but much more resulting motion going to the throw out bearing. This was one of my attempts to solve the problem of making sure that the clutch was in fact disengaging EVERY time. A hydraulic system is simlply the leverage of a large master cylinder bore in relation to the line size. i.e a 8mm bore with a 1 mm piston is a 8:1 mechanical advantage. An 8 mm bore with a 2 mm piston is a 4:1 advantage. Vs a 10" clutch pedal with a pushrod attached only 2" inches from the pivot giving a 5:1 advantage. These measurements are only approximate, but hopefully readers will get the idea.

Chuck

wfo76

might try this test

idle in neutral for one minute
push clutch to floor for 5 seconds
attempt to shift directly into reverse
if it does not grind, clutch is fully releasing

this assumes the TKO does not have a synchronized reverse

DaveL82

Markus,

I tried to run a hydraulic system but was never able to get enough movement from the slave (not enough release from the presure plate). I tried finding smaller dia. slave cylinders to give more travel however wasn't able to find one that could mount easily (verticle or front side flanges).

May revisit this in the future, however I had too many other projects to finish so went back to mechanical for now.

evalu8r

I had a little trouble with mine. I ended up pulling the rubber pedal bumper from under the dash allowing the pedal to pull up higher which in turn let more fluid into the master from the reservoir. Sounds goofy, but give it a try.

Chris

zwede

Dave, what procedure did you use to bleed it? Could you have had some air trapped?

DaveL82

Markus,

I used the GM truck master cylinder and bleed the master by releasing the line at the master connection and also tried tilton units with a bleed port (loosen line/port, slowly push down and hold with block of wood against seat, tighten line or port, slowly let pedal up, loossen line/port, repeat). Was sure the air was removed. Also used gravity bleed on the various slaves and then presure bleed through bleed port. Even so I still didn't have enough travel on the throw out arm.

When I used the Tilton master cylinders I had to make an angled shim to point the master down and away from the hydroboost (similar to truck master offset).

I would like to add that I used a pull type slave on my truck which worked great and pull type has more travel! It's a $70 dollar wilwood unit from summit. The problem is room to mount it on the vette! Even thought about mounting it near the back of the trans and using a cable to pull the arm but the arm anchor point is in from of the foot well.

zwede

Now if the engine was actually running this would be a great idea. But, alas, the engine still needs plenty of parts before it will run.

Durango_Boy

The engine doesn't have to be running to test, but it help being about to use the gears as normal driving would allow.

DaveL82

Markus,

I used to used a feeler guage to check freeplay may years ago on an old race monza. I think it was 15 thou between flywheel and disk however I would try a google search to be sure. It was a good way to check with the engine not running.

BerniesVette

You probably need to install an adjustable clutch fork pivot stud to locate the clutch fork as close to the pressure plate as possible. This allows less travel for the fork to disengage the clutch plate. I had to adjust mine about 3/4 of the way out to get it to disengage. I used an '85 one ton master and slave cylinder and it works beautifully. This system will bleed itself almost as everything is lower than the resevoire. I used a remote resevoire from a Honda Civic that cost $5.00
The adjustable pivot stud is all you need to get your clutch working.
Bernie

Durango_Boy

See, even with no C3 anymore you're still one of the best we have.

BerniesVette

Once a gearhead always a gearhead! I hope this helps because hydraulic clutches are the only way to go! thanks Durango!
Bernie

Durango_Boy

I know. I am already planning my next Vette. A '73, 454, T5, and Hyd. clutch conversion. It'll be a few years down the road, but I have all your posts and threads on how you did it for reference. I love planning ahead.

zwede

I found the spec on the Novak site: Diaphragm clutch needs a 0.030" air-gap. I'll try to measure it tonight. Novak says their slave is designed for a 3/4" to 7/8" bore master. The 85 truck master we're using is 17.75mm, or a little over 11/16". Slightly small... I need to check the bore of the Novak slave. I also have a 85 truck slave laying around I could use which is 13/16". If the Novak slave is more than that, the 85 truck slave might be a better match.

BerniesVette

Zwede,
Good luck on your project. Yes, you do try to match the bores, that is why I went with the 85 master and slave combo. I think Novack has both cylinders too. The adjustable pivot stud is almost a necessity to fine tune the clutch fork distance.
Bernie

zwede

already have the adjustable pivot and it's adjusted pretty high (fork forward).