tjZ06

I did search and found some good threads, but I still have a bucket of questions about the QM clutches.

• Do any CF vendors sell them?
• What is the right setup for a 3100lbs 600 RWHP C5Z?
• Just how on/off are they?
• Could they be used in a car that is also AutoXed - i.e. if I have to bump it up through the staging lanes is that going to kill the clutch (I really don't want to have to be one of those guys that has to push his car up as his line moves to the start)
• What do they actually weigh?
• Other things I need to consider (I did read about the adapter you need to make for the slave line coming off the master, as well as setting a clutch pedal stop)

My other option would be an RPS Billet/Carbon triple (no cheap proposition itself) that is still pretty damn light, holding up to over 900RWHP (and over 800RWTQ) in my buddy's ~3200lbs C6Z06, and is street drivable (somewhat on/off and it chatters if you get it wrong, but I was just rolling around in the 900RHWP C6Z last night and it wasn't bad).

-TJ

bb69

My buddy as a QM 5" (maybe 5.25 or 5.5, but you get the idea) in his ASA car behind a LS1. The engine makes about 500HP and the car weighs 2600. I have driven it a number of times and can tell you that it is absolutely on/off. With no flywheel, you can't just bump the car forward. Unless you get the wheels spinning, you're going to stall it.

I would avoid starting and stopping as much as possible. When it does slip, it can easily destroy the reaction plates as well as the friction plates. By the time you're done replacing all that, it's $1000 just in parts. These clutches do not like to slip at all.

I assume most of this applies to a full body Corvette, but your mileage may vary. I am also assuming you are talking about using this clutch without a flywheel. If you were using it with a flywheel (I don't even know if you can) some of these problems would go away.

Ken

tjZ06

As far as I know all QMs have no "flywheel" in the typical sense. They have their own tiny flywheel (as seen in the 2nd pic here http://www.davidfarmerstuff.com/quartermaster-C5.pdf) but they do not use a full-size flywheel. That is the style I'd be using.

I also wonder how this even works out for ppl that do HPDEs. If you're starting from pit-lane and are back in the pack some you might have to bump forward a few times. Some groups I run with have the "starter" walk back so that the cars don't have to scoot forward, but some groups expect you to come up to the starter (lame).

-TJ

tjZ06

Oh, and the big question... what do they cost?

-TJ

davidfarmer

the parts required are on my pdf linked above, you can get pricing from any racing vendor, say HRP etc

505178 5.5" flywheel
505007 crank bolts-metric
395090 clutch assembly
305508 clutch bolt kit (bolts clutch to flywheel)
730015 bearing adapter to torque tube
730185 release bearing

You use an OEM automatic flexplate from a Camaro for simply starting the car (ring gear), and the actual flywheel is a 5.5" button flywheel as seen in the PDF.

Removing the steel flywheel and clutch will reduce your mass from around 50lbs to around 20lbs....more or less...

redvetracr

no reverse drive starter available? that will reduce your "moment of inertia" even more.

drivinhard

On mine, the stock flywheel/plate/disc was 51 lb. QM 5.5" V-Drive is 8.9 lb, and the OEM automatic flexplate was 5 lb (IIRC).

It is a substantial difference in the real world performance of the car, especially in the lower gears.

davidfarmer

during my pro days, no one made a reverse-drive and starter ring......it wasn't legal in World Challenge anyway.........well not until Cadillac came along a re-wrote the rule book.

There probably is a setup now.

drivinhard

mine is pretty aggressive, but it's nothing like that. I have only stalled mine a handful of times since the install.

if I have to slip it, it is for a very short duration, and I try to keep the revs down. having the short 1st gear of the M12 helps get it locked up and rolling quickly, if you had a really close ratio road race gear box with a tall 1st gear, it could be a pain

the best thing about it, is the much much better than OEM hydraulics. full release, every time, in any situation.

it is a lot trickier to install than a stock style clutch

0Vector Vette

You might want to consider Quartermaster 8.5" twin disc. That is what I am running in my car. Substantial weight savings, though I don't remember the exact number, it was more then 20 pounds. Much better hydraulics, better clamping force. It is not quite an on/off style clutch, though it is close. If you are talking about moving up one car length in line, then you probably won't like it. You can get it going though without doing a burnout. I will not load the car on the trailer with it though.
Robert Finlayson
Performance AFX Motorsports

davidfarmer

I agree with drivinhard that the 5.5 can be slipped quite a bit, although you want to avoid it as much as possible. I ran several seasons with them in World Challenge where I DROVE the car into the trailer.

I also don't find them difficult to install, just drilling a hole for the new hydraulic lines, and having a fitting made up, make the initial install a bit more time consuming. After that, it's very straightforward.

tjZ06

I ended up just going with an RPS Billet/Carbon triple since I still want to be able to pull the car on/off trailers, bump it up easily at AutoX or on grid at track days, and maybe even street drive it a tiny bit.



Thanks for all of the advice/help regardless!

-TJ

briannutter1

This is pretty much my experience too. I've got the 8.5" to replace the stocker in my c5z. went from exactly 50 lbs to exactly 25 lbs. I drive it on the street and just put about 1000 miles on it over the last two weeks. I've gotten used to it, but I did stall it quite a few times initially. Quality of the unit is very nice. Pedal pressure is heavier than stock, but not overly so. Hydraulic issue solved. Clamping is fine. Noise isn't bad, but I do find myself doing a quick clutch bump if the plates start to rattle at idle (in neutral) and it seems to mute it. I use their steel billet flywheel and did find the hydraulic connections are further forward of the stocker, which either requires die-grinding the bellhousing openings about .375" with a diegrinder. I did wonder if anyone has ever put 90degree fittings on the slave that clock the threaded portion backward to move the lines further back (so they don't kink where they exit the bellhousing). I was asked which disks I'd prefer based on the torque. I'm building a 600 ft/lb big cube shortblock soon, so went with the metalic rally disks. Looking back at it, if they have an organic option...I might have run those disks until I actually do the shortblock. Even as it stands, I've gotten the "muscle memory" down to do it without spinning the tires. Rest assured, there are quite a few different twin disk units available from different manufacturers, and I'm "relieved" that I got the quartermaster. I could have spent a whole lot more money on this experience. Glad I didn't go any lighter than 25 lbs total for my usage.

J.R.

The 8.5 in quartermaster with twin rally material discs and lightweight steel quartermaster flywheel will work. It is not on/off unless your running a 1.75 first gear. The rally material on disc (.250 rather than .105) makes it a sweet setup.

drivinhard

I will check the disc wear tonight, as I've had it in since july and run 5 days on it, plus some street driving (rural street driving, not city stop and go)

I can vouch this was an honest .75 sec/lap (free rules) mod. There are 2-3 pt mods in TT/PT rules that won't even get you half that.

throwit

Was that gain in comparison to the stock clutch? or is that compared to a lightweight spec?

drivinhard

coming from stock LS6 (~51 lb) to ~14 lb and 5.5" dia

sperkins

cheater

drivinhard

checked the discs tonight, no visable or measurable wear after 5 days and a decent bit of street driving. no dust/residue in the bell housing.

so far so good. it's got a bit more chattery as it's worn in, but it is what it is. the manors/engagement/noise is a non-issue for what I do with the car.

Jason

pot