Clutch 1

Today, there’s a wide array of clutches available on the high performance market, from complex race-only equipment to street only pieces.  In between are some pretty neat combinations – hardware that is perfectly suited for both the street and the strip.  And like the race-only gear, it ranges from basic to sophisticated.  What follows is a look at two very different clutch “systems”.  Check it out.  The range of possibilities is endless.

Back-to-Basics

Yesteryear has a melancholy pang to it.  Plenty of folks pine for it. Some cling to it. Certainly, as writers, we dig the “modern” computers we use for writing these pieces along with all of the other “modern” things they can do for us, but when it comes to cars (all sorts of cars), yours truly just happens to like stuff that can be fixed.  And fixed easily (OK….we suspect it has something to do with old age and familiarity, but lets not go there!).  Now, as it turns out, we also happen to dig stick shift cars.  And for us at least, clutch assemblies fall into that simple (and familiar) category.

Way back when (or at least in the 1970s), the clutch package to have was a Borg & Beck/Long combination pressure plate, a sprung hub disc (with a Marcel) and some sort of steel flywheel.  There was a very good reason for this combination.  Most will recall that the old diaphragm pressure plates found behind most Chevy’s (and other GM products) offered pretty good pedal feel, but they often had one ugly tendency:  They could stick to the floor at wide open throttle.  Not exactly good.  And cast iron flywheels (of any sort) weren’t exactly good news either. When (not “if”) they decided to depart, they had a tendency to take big chunk of the car with them.  If you didn’t have a scattershield, then your personal body parts were at the mercy of the departing hardware too.  As far as the discs were concerned, some of the really good ones happened to be copies of Chevy’s L88 Corvette disc.  They worked and the springs never rattled out.  Overall, it was a dirt simple arrangement. It got the job done and unless the clutch was incredibly abused, it seldom failed.  And if and when the clutch package needed service, the steps required for maintenance were equally dirt simple.  Life was good.

That was then. Time and technology marched forward.  Sophisticated multiple discs became the norm. Disc diameters shrunk (some by dramatic margins).  Some setups seen in racing circles went from two to three or more discs.  Soon there were a lot of different pieces contained within the bellhousing.  These new clutch packages are obviously fabulous with light pedal pressures, great clamping power and so on, but to me at least, they lack one basic ingredient:  They’re not exactly simple.

So what’s a guy to do – especially if you’re like us and stuck in what some might consider a forty-or-so year old simplicity time warp?  That’s easy. Just check out the following.  You’ll still find hardware of choice from the Seventies (and in future issues, we’ll look at some much more modern technology). But even with the advances, the basic premise for a back-to-basics clutch package is the same:  A Borg & Beck/Long combination pressure plate, steel flywheel coupled with a sprung hub disc.

In the photos and captions that follow, we’ll take a close look at today’s old (new) single disc clutch setups from the folks at McLeod.  Check it out. If you yearn for the simplicity of yesteryear, this clutch setup is for you.

 

This is the 25-pound steel, 168-tooth ring gear flywheel we used behind a 427-inch big block Chevy.  When considering flywheels, you’ll find there are plenty of different weights.  Typically, they range from 25 pounds to 30 to 40-pounds for most Chevy’s.

This is the 25-pound steel, 168-tooth ring gear flywheel we used behind a 427-inch big block Chevy. When considering flywheels, you’ll find there are plenty of different weights. Typically, they range from 25 pounds to 30 to 40-pounds for most Chevy’s.

 

Why the need for different flywheel weights?  Simple.  A 283-powered ’62 Impala is going to need a whole bunch more flywheel weight to get the mass moving than an L88 in a 1969 ‘Vette.  You’ll need to specify the engine balance (internal or external) for your specific combination when ordering a flywheel.  You’ll have to consider diameter, and obviously ring gear configuration too.

Why the need for different flywheel weights? Simple. A 283-powered ’62 Impala is going to need a whole bunch more flywheel weight to get the mass moving than an L88 in a 1969 ‘Vette. You’ll need to specify the engine balance (internal or external) for your specific combination when ordering a flywheel. You’ll have to consider diameter, and obviously ring gear configuration too.

 

It’s not a big piece, but it’s extremely important. This flywheel carries an SFI sticker.  That means it’s technically legal for sanctioned drag strip use. Even if your car never rails down the 1320, the SFI sticker should bring peace of mind, because an identical flywheel passed a stringent independent SFI test.  In that procedure, the flywheel did not fail during a rotational test and post inspection didn’t reveal signs of failure such as cracks, discontinuities or elongation.  As a manufacturer, you only get the sticker when the product passes the test.

It’s not a big piece, but it’s extremely important. This flywheel carries an SFI sticker. That means it’s technically legal for sanctioned drag strip use. Even if your car never rails down the 1320, the SFI sticker should bring peace of mind, because an identical flywheel passed a stringent independent SFI test. In that procedure, the flywheel did not fail during a rotational test and post inspection didn’t reveal signs of failure such as cracks, discontinuities or elongation. As a manufacturer, you only get the sticker when the product passes the test.

 

What you’re looking at is something that McLeod pioneered – and it’s something that goes a way back in time.  What McLeod did was to craft a special pressure plate that uses the heavy-duty hat of a Borg & Beck clutch, but with Ford Long style levers.  The Borg & Beck configuration allows the pieces to fit in Chevy applications.  Remember back in the good old days we used clamping loads that were massive?  That added up to stiff (some super stiff) pedal pressures.  That’s not entirely necessary today, given modern disc materials.

What you’re looking at is something that McLeod pioneered – and it’s something that goes a way back in time. What McLeod did was to craft a special pressure plate that uses the heavy-duty hat of a Borg & Beck clutch, but with Ford Long style levers. The Borg & Beck configuration allows the pieces to fit in Chevy applications. Remember back in the good old days we used clamping loads that were massive? That added up to stiff (some super stiff) pedal pressures. That’s not entirely necessary today, given modern disc materials.

 

As a result, you can get away with a 2200-pound clamp load clutch – and that’s what this one is.  McLeod offers similar pressure plates with clamp loads ranging from 2200 to 2400 to 2700 pounds, if you’re so inclined. Additionally, they’re available in varied bolt circles, and with or without counterweights.  Watch for more info on this setup in the next issue.

As a result, you can get away with a 2200-pound clamp load clutch – and that’s what this one is. McLeod offers similar pressure plates with clamp loads ranging from 2200 to 2400 to 2700 pounds, if you’re so inclined. Additionally, they’re available in varied bolt circles, and with or without counterweights. Watch for more info on this setup in the next issue.

 

 

Source
McLEOD RACING
1600 Sierra Madre Circle
Placentia, California 92870
Ph: 714-630-2764