Clutch Master Cylinders

The Camaro unit is supposedly the "hot setup" for street rods because it is so compact, but Wilwood also offers master & slave cylinders:

The Camaro set-up should fit without much work. I used the set-up from an S-Series on the 4.3 in a Vega I had a few years ago. Plenty of room.

Hydraulic clutches have been around for some time. It was the slick way to go years ago when friends were building their own dune buggy's. Back then they had pedal kits (clutch, brake and throttle too as I recall) and slaves to go with. A quick Google search brings up a bunch of stuff. Maybe some place like this:

I can't help on you question, but if there are any GM clutch master cylinder experts out there I'd like to hear from them. I've been fighting with the POS GM clutch MCs on my truck for quite some time and am about ready to fabricate my own MC and be done with their garbage. I'm not sure the slave cylinder is much better either, but it's more work to try to fabricate one. The problems I keep having are with intermittent failure to release, very irritating.

You might also try alt.trucks.chevy, since a truck part is involved.

Do you have a picture or ten? One thing I didn't mention is that it looks like the push rod from the pedal needs to go right through the fuse panel.

Or did you just move/replace the fuses as a matter of course?

Tim, that's about as simple a hydraulic project as there is. The pressures are laughable. The only real consideration is whether the volume of the MC is sufficient to move your slave piston the required distance. There are dozens of of clutch master cylinders available in the aftermarket hot-rod catalogs. I'd bet money you aren't the first one to do this exact project. Persoanlly, I'd call Craig Taylor at Taylor Engineering in Dallas. Nice guy, very helpful, and I bet he can tell you exactly what you need off the top of his head.

Any chance that you have had the flywheel ground?

Way back, when GM first went to the hydraulic clutch in there pickup trucks this caused headaches. My brother-inlaw had his flywheel ground when he replaced the clutch. Then he had problems getting it to release. Back then they had two special spacer plates to solve the problem. That was what he ended up having to do, tear it back down and install a spacer plate (between the flywheel and motor side).

Personally, I would much rather have a mechanical clutch :)

Not me! I've dealt with bent forks, bent bellcranks, stretched and broken cables for decades. Make mine hydraulic. For that matter, the concentric slave cylinders are pretty slick if they weren't so hard to change out.

Was it Saab that mounted it on the front of the engine where it was easy to get to?

No grinding or anything, just continual clutch no-release problems. Clutch replaced once, coaxial slave cylinder replaced another time, MCs replaced like four times. Never had a problem with clutch slip, only failure to release.

Now that I have a new truck, I'm getting ready to pull the clutch on the old one myself and see if I can fix it for good. This truck also ate rear axle seals until I got into it. Axles seals replaced under warranty several times, when they went again out of warranty I replaced them myself and haven't had a problem since (195k+ now).

Wasn't hard. Just made a simple plate out of 1/8". Welded it in place and used that plate to mount the clutch master. I did alter the push rod length so that the mounting flange was inside the firewall and remote mounted the reservoir. I have also seen one mounted out in the air duct, that one had a long bell crank shaft to reach it.

Moved the fuse box on mine because I built my own wiring harness anyway. Used a painless box and universal kit.

The last built rig I had went down the road a few weeks ago. That was an Olds Starfire GT (Monza clone) that I stuck a well tuned 3.8 turbo in. That car had a 5 speed behind it and could really stick to the road.

Current project beast is a 70 Nova. It will end up with a perimeter frame, 'vette rear suspension, tubular A arm front suspension (current plan is coil overs but may use torsion bars instead) Current power plant idea is an injected big block. Might make it a green mobile and burn alcohol!

Step down and no release? If you step down a second time does it release then?

Yep, makes it kinds difficult to shift. Bit of a problem when you need to stop as well.

Nope, pump it a half dozen times and you might get it to release enough to shift with a clunk. Doesn't do it all the time either, can be working just fine then start acting up.

I have no good way to monitor it for testing, but I suspect the MC reservoir valve isn't sealing well allowing some of the stroke output to simply go back to the reservoir.

I expect I could fabricate a better MC setup and add a bit more displacement as well since I've always felt it bordered on not enough displacement.

You need the same overall mechanical advantage - main thing is the bore of the master cyl - assuming the leverage on the pedal is the same.

Measure the bore of the clutch slave and the master of the original install - calculate ratio. Then calculate the mechanical advantage of the clutch pedal as a lever. Multiply them for the total MA.

If your replacement setup is close, you are OK. Low MA makes a heavy pedal.

How close is the fluid line to a manifold? How old is the fluid? Sure sounds like vapour fade due to inferior fluid or overheated lines.

Not particularly close, probably 6" from the manifold, 3" from the pipe heading down to where it crosses under the clutch bellhousing.

A month or so since I last replaced the MC and flushed a good pint through and out the coaxial slave cylinder breather.

Sounds like it, and some of the cases of it acting up have been after it's had some time to heat up, but other have been acting up from cold.

I suppose I could find some insulating wrap and wrap the line. Not sure on inferior fluid, it just uses DOT3 brake fluid. The last couple pints have just been generic DOT3, is there a particular brand I should look for?

DON"T use heat wrap - use a properly positioned heat sheild and you should be using DOT4 fluid, not DOT3.. The best heat sheild is a stainless steel sheet midway between the heat source and the tube - or half of a 2" stainless steel tube mounted so it semi-surrounds the tubeing, about 1" from the tubing.. Three inches from the crossover without a heat sheild is TOO CLOSE. Might get by with DOT4 or DOT5 fluid, but you are still pushing it.

How are you bleeding the system? The preferred method is to pull a vacuum on the top of the reservoir and drawing out any air.

When you pump the pedal is the effort different than when the clutch does work?

It almost has to be on the top if your not using any fluid. Perhaps pull the master and see what the bore looks like, it almost sounds like the piston seals are bypassing fluid.

snip

I don't know this application - on the cars I am familiar with with hydraulic clutch, there is no "pump" in the master cylinder, so any air in the system is critical - the only and I mean ONLY way to bleed these (on this particular car) is via a pressure bleeder. Air in the system will cause the kind of effect described.