Upgrading OE Clutches To McLeod Performance Parts - Clutch Can Horse Tamer

There are two key requirements to a daily driver: It has to be reliable and always ready for action. My "low-buck" '69 Dart, originally a 273/automatic, is now running a warmed-over 318 and overdrive four-speed. Unfortunately, it has recently been a case of "once bitten, twice shy" as far as swapping-in junkyard components are concerned. First, the junkyard OD four-speed turned out to be toast, so it had to be removed and rebuilt ("Overdrive Overhaul," Mopar Muscle, Oct. '01). Second, the junkyard clutch cover out of the F-Body donor car and a Cheap-O Autoparts replacement clutch disc were useless. Though the cover looked like new and the disc was replaced, the clutch simply wouldn't hold torque. An off-the-line dump would smoke the clutch, not rubber, and one-two power shifts would break the clutch so loose it wouldn't catch without lifting.

Though the clutch chattered violently on engagement, the Dart would still get down the road, but when handling impromptu street action, it was seriously handicapped. Delicate movement on the clutch and rolling starts were enough to handle the average contender, but crunch time came when confronted by a 2,600-pound Mercury Comet (Maverick style) sporting a hot Ford small-block. It was as fast as it was ugly. The pull in First gear was bumper to bumper, but counting down the revs as the tach neared seven grand, I knew the gig was up. Slamming Second, the clutch was smoked, and so was my Mopar. The time had come to lose the junk.

We tapped McLeod Industries for the serious hardware. McLeod manufactures the broadest ranges of performance clutches in the industry, with a reputation for quality. We figured with their extensive product line, they would have a clutch component combination well matched to the Dart's requirements.

Moreover, the raw truth is that "routine" 6,800-rpm shifts with the stock flywheel and junkyard OE clutch were attended by nervous thoughts of a metal-and-flesh-sawing clutch explosion waiting to happen. First on the shopping list was a new McLeod SFI-approved steel flywheel. The next decision was the pressure plate style. McLeod offers a full range of covers, including the stock Borg and Beck type, the diaphram style, the Long type, and McLeod's unique Borg and Beck/Long hybrid.

Borg and Beck's come with a 6.0:1 finger ratio and increased holding power comes from a combination of spring-load and centrifugal-assist rollers. The centrifugal assist varies with the number of rollers. Adding rollers increases the centrifugal assist, but the downside is B&B clutches lock up at high rpm. More rollers lock up at a lower rpm, making high-speed shifting difficult or impossible. Hemi cars came with three-roller B&B clutches rather than the six-roller design used in other big-blocks for this reason, and cheap rebuilder's B&B pressure plates often have all of the assist rollers removed.

Diaphragm clutches are much lighter in pedal effort for a given clamping force, have no centrifugal effect, and don't use ridged release levers, using flexible spring-steel levers instead. Generally, the diaphragm clutch is considered too delicate for full competition use. On the other hand, Long pressure plates have a quicker-releasing 4.8:1 lever ratio and is the preferred style for true competition use. Long's operate through a combination of static and centrifugal clamping, gaining centrifugal assist directly from weighted levers imparting the additional clamping load. Since the conventional Long cover won't fit in a Mopar application, this is where the McLeod Borg and Beck/Long fills the gap. The McLeod B&B/Long combines the operational features of a Long clutch in a heavy duty B&B-style hat. Though the Dart isn't a race car, with the way it's continually hammered on, a B&B/Long was the choice for our application. The McLeod B&B/Long pressure plate will accept either a 10.5- or 10.95-inch disc on a common Mopar 10.5-inch B&B bolt pattern flywheel.

The last choice was in the clutch disc. Again, McLeod offers a wide range of discs, from street replacement types to iron-faced, to multi-disced street/strip and race units. We consulted McLeod's tech line and let them pick the disc for our combination. We went with a No. 260821 Dual Performance 10.95-inch disc, which features a combination of Kevlar(tm) and asbestos facings on the flywheel and pressure plate sides, respectively. Though it's a high-performance disc, the marcel layer under the friction lining provides a smooth take up. Rounding out the parts list was a new throwout bearing, which comes from McLeod already installed on a new slide collar.

The McLeod components bolted-up with the ease and fit of OE replacement parts, but on the road the Dart's new clutch setup bites like no OE clutch ever could. The performance grip was there, but what really got our attention was how smoothly the performance clutch engaged and disengaged. Off-the-line chatter is nonexistent with this combo for silky-smooth starts in normal driving. Sidestep the clutch, on the other hand, and the bite is right now, setting the tire ablaze. Okay, Comet dude, bring it on now....