|......Camaro- Untold SecretsFeature Article|
the most interesting, rare and overlooked high performance options available for the early
Camaro is the Heavy-Duty Dual Disc Clutch, Regular Production Option MA6. This heavy-duty
(HD) performance option was first released for use on the high-performance optional
engines during the 1969 model year. The intent was to offer a clutch system that would
stand up to rigors of performance driving and, as it turns out, the design may have been
overkill. The durability of this clutch is absolutely amazing; combinations similar to
this were used as slider clutches in dragsters handling well over 1200 horsepower!
The unit is especially well-suited for use with the Z/28-302 in conjunction with the M21-M22 transmission using the 2.20 first gear and any rear axle ratio numerically lower than 4. l 1: l . The combination of the 302 being relatively low on torque at the bottom end and the standard gearing being relatively stout requires higher revs and more slipping of the clutch to get rolling at a moderate pace. Even more revs and clutch slippage are required to get off smoothly and quickly. This action substantially reduces clutch life and the standard 10-1/2" clutch with its marginal performance characteristics was a compromise at best. In recognition of this, Chevrolet offered the optional HD dual-disc clutch. Unfortunately, the high cost of the option was a factor that kept it from being ordered on many cars. In fact, if a car was to see any real high-performance work, standard protocol of the day was to replace the stock unit with one of the lower priced high-performance aftermarket units. We know today in retrospect, however, that the dual-disc system was far superior.
Here's a comparison of an 11" clutch disc with the driven disc from the MA6 option. The discs used in RPO MA6 are 10" in diameter, but the use of two greatly increases the amount of abuse the clutch system can take.
The HD dual-disc flywheel weighs 24-l/2
pounds and the diaphragm cover with two driven discs and a 10" center plate weighs 30
pounds, the total of which is approximately equal to the standard BORG and BECK unit at 33
pounds for the flywheel and 21 pounds for the cover and plate. It is important for the 302
to maintain momentum by using a heavier flywheel-clutch combination such as this, whereas
the big block can use a lighter unit like the 15 pound flywheel developed for the L88.
This is due to the big block's greater torque enabling it to pull through the lower rpm
range. A heavier flywheel maintains the engine's momentum by keeping kinetic potential
high which in turn requires higher revs to do so, and since the 302 powerband is found in
the higher rpm range the dual-disc/302 combination works extremely well together. If, for
example, you were to use the 15 pound flywheel with the 302, the decrease in kinetic
potential would bring engine rpm down under load, out of the powerband causing a bog on
takeoff and upon each subsequent re-engagement to the next higher gear.
Total disc face area is 201 square inches, or roughly double that of a standard clutch setup. This larger surface increases the amount of abuse the clutch can take, an important feature considering this unit was installed behind high-revving 302s and ground-pounding high-torque big blocks.
The 11" disc on the left uses 5 springs to absorb shock, while the dual-disc plates use 6. In addition to the dual-disc's ability to take abuse, the pedal effort is light and the "action" is exceedingly smooth, reducing driver fatigue during endurance races.
decreased pedal pressure is most significant with regard to the reduction of fatigue
associated with road racing commonly encountered in events such as TRANS-AM, CAN- AM and
NASCAR racing. Basically, these are endurance events, testing both man and machine, with
races that span 1-2 hours of extreme high-performance driving. Imagine how it feels
getting stuck in traffic with a stick, and compare it to how it might feel to shift
continuously, one thousand times in a two hour endurance event!
The benefits of using the HD dual-disc system in drag racing begin with its ability to efficiently manage tremendous horsepower and torque loads allowing for a more controlled launch. In addition, using the smaller 10" diameter clutch housing and discs results in a decrease in centrifugal force which lowers the chances for explosion and promotes increased rpm usage. From racing experience, Chevrolet Engineering clearly knew the advantages of these HD units - and now so do you!
While no official numbers exist in Chevrolet archives, it could be said that it enjoys a place among the lowest volume high-performance options ever sold, if not THE lowest.
|RPO MA6 HEAVY-DUTY CLUTCH (DUAL DISC)
DURABILITY AND SAFETY FEATURES
MA6 systems use a dedicated, 14" flywheel (casting number P 8999 NF) made of nodular ferris cast iron. Flywheel weight is 24 pounds. The pressure plate used in the dual-disc system is the typical GM diaphragm type. Total system weight, including flywheel, pressure plate and discs, was 54 pounds.
"The dual-disc system is well suited for extremely heavy-duty use on strip or track, including road racing. Also suitable for street use creating a new driving experience."
This is a copy of part of an order sheet for 1969 Camaros. The MA6 heavy-duty dual-disc clutch option is seen about 1/2 way down. The option was obviously overlooked by most people ordering a performance Camaro. The MA6 clutch is most probably the lowest production performance option offered for the Camaro in '69. Those were the days . . .
This article originally appeared in the Summer 1996 Issue of YEAR ONE's Restoration Review magazine. Restoration Review is intended as a forum for and about the vintage automobile restoration hobby. For more information about Restoration Review or to subscribe please call YEAR ONE today ! 1-800-950-9503.