Clutch Master Cylinders

I'll ask my _second_ question _first_, so you can think about it while you read my first question: What's a good newsgroup to post this sort of
question? I hate fora, so if there's an active newsgroup that'd be vastly preferred.
My _first_ question is: are all clutch master cylinders created equal?
I'm putting a 2.8L V-6 into a Vega (to be followed by a 3.4L V-6 from GM Performance Parts, if they survive the bankruptcy). I'm doing this instead of a small block V-8 because I'm crazy, because the 2.8 block lets be get at the spark plugs without jacking the motor up, and because it'll help retain a halfway decent balance fore and aft (I hope).
Because I'm crazy I'm retaining the stick shift of the original, so I need a clutch linkage. The transmission that fits well is from an '87 Camero (with 2.8L V-6), but it wants a hydraulic clutch instead of the cable clutch which came on the Vega and the S-10 that donated the engine.
For a variety of reasons (mostly having to do with the advisability of welding on unknown alloy cast aluminum) I don't want to modify the Camero bellhousing. The S-10 bellhousing won't fit.
So I'm planning on finding the correct Camero clutch slave cylinder parts that'll just bolt onto the bellhousing, but that leaves me with needing to get the master cylinder mounted onto the firewall. I already know it'll be a bitch; I'm planning on getting all of the Camero parts I can (both pushrods, both cylinders, even bolts and tubing if I can). But if the Camero master cylinder just won't fit, how much leeway do I have in finding something that will? Do I get just any old thing? Is there an interchange book that's accessible? Are different master cylinders with different bores readily available, and how much can I compensate for differing pedal-to-pushrod mechanical advantages by changing the master cylinder bore? Are there any other differences I need to know (surely there are some valving issues -- anything else?).
TIA.
--
www.wescottdesign.com

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The Camaro unit is supposedly the "hot setup" for street rods because it is so compact, but Wilwood also offers master & slave cylinders: http://www.wilwood.com/Products/006-MasterCylinders/005-CSBMC/index.asp

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Tim Wescott wrote:

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.
--
Steve W.

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On Tue, 21 Jul 2009 14:16:24 -0400, Steve W. wrote:

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?
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Tim Wescott wrote:

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!
--
Steve W.

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On Tue, 21 Jul 2009 12:03:46 -0500, Tim Wescott
<snip>

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:
http://www.classicchevy5speed.com/Hydraulic-Clutch-Kit.aspx
Your the best one to decide if you want to get a ready made aftermarket kit or piece something together and hope for the best (shrug).
--
Leon Fisk
Grand Rapids MI/Zone 5b
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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.
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On Tue, 21 Jul 2009 13:26:27 -0500, "Pete C."

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 :)
--
Leon Fisk
Grand Rapids MI/Zone 5b
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Leon Fisk wrote:

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?
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Leon Fisk wrote:

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).
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Pete C. wrote:

Step down and no release? If you step down a second time does it release then?
--
Steve W.

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"Steve W." wrote:

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.
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wrote:

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.
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snipped-for-privacy@snyder.on.ca wrote:

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?
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wrote:

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.
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snipped-for-privacy@snyder.on.ca wrote:

I'll see what I can find to fab a shield. What about heat wrap on the pipe where it crosses under?
If I change to a DOT4 or DOT5 fluid what kind of cleaning would I have to do and would there be seal material compatibility issues? Brands of fluid to look for?
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"Pete C." wrote:

I see that there is a Valvoline brand DOT3/DOT4 fluid rated at 480 deg F and seems to be compatible with regular DOT3, so I should be able to upgrade by just flushing that stuff through. I'll also put some heat wrap around the exhaust pipe in the problem area to try to keep the heat in there, and fab a radiant shield (probably AL since I have material) to put between the pipe and clutch line.
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wrote:

DOT4 is a direct compatible replacement. Dot5 requires a flush - generally alchohol or BrakeKlean.
I'd go with Dot4 for simplicity. Heat wrap causes premature pipe failure.
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snipped-for-privacy@snyder.on.ca wrote:

there is now a DOT 5.1 that is another breed altogether. Apparently it's non-silicone and has some compatibility with other types.
www.stoptech.com
DOT 5.1 fluids!
Historically, DOT 5-level performance (specifically boiling points and viscosity) could only be achieved with silicone-based fluids. However, modern compounding has created glycol ether-based fluids which now meet DOT 5 bogeys in these key areas. Consequently, the DOT 5.1 moniker was created to differentiate between these two very different chemistries which both meet DOT 5 performance requirements.
In so many words, DOT 5.1 fluids are simply DOT 4-type fluids which meet DOT 5 performance requirements. Because of this, they typically can be mixed with DOT 3 or DOT 4 fluids without concern. In some circles, they are even referred to as DOT 4 Plus or Super DOT 4 fluids because they are more similar to a conventional DOT 4 fluid by chemistry than they are to a conventional DOT 5 fluid. In fact, DOT 5.1 is essentially comprised of Borate Esters.
While it may not be obvious, the big advantage of the DOT 5.1 fluids is that they contain all of the nifty water-absorbing characteristics of the DOT 3 and DOT 4 fluids while simultaneously providing for very high boiling points and relatively stable viscosity over a wide range of temperatures. The best of all worlds, you could say. The table below sums it up quite nicely. PROPERTY     DOT 4     DOT 5     DOT 5.1 Dry BP (F)@ 0.0% H2O     446     509     509 Wet BP (F)@ 3.7% H2O     311     356     356 Chemical Composition     Glycol Ether / Borate Ester     Silicone Based Glycol Ether / Borate Ester
(As stated earlier, the table data above contains the minimum properties for a fluid to be called a certain type. For example there are many racing brake fluids with Dry BP performance at or above 590o F and Wet BP at or above 390o F.)
So, what is the downside of the DOT 5.1 fluids? Like most things in life, the good stuff isnt cheap. DOT 5.1 fluids typically cost three to four times as much to manufacture as a conventional DOT 4 fluids. Theres always a catch
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RBnDFW wrote:

Given the small quantities used, I would expect the cost difference is pretty negligible.
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