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GET DOWN
With some mild mods, suspension expert Trevor Harris makes the Monroe Handler Mustang Cobra handle like the stree performer it is.
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The cosmetic treatment by Dave Kent's Creative Car Craft, and the wild paint, are generally enough to convince people that our project Monroe Handler Mustang is a legit road racer, when in fact it is completely street-legal. But looks are nothing without performance, so the next step was to match the Mustang's ride and handling to its racy appearance.
To accomplish this, the externally finished car was taken to Harris Dynamics (1945 Placentia Avenue, Building F, Costa Mesa, California 92627). The proprietor of the firm, Trevor Harris, designed and built suspensions for the famed BRE Datsuns which won several Trans-Am and SCCA national titles, for the AVS Shadow Can-Am effort, and for Brad Frisselle's 1976 IMSA champion Datson 240Z. A street 302 V8 Mustang, with low-hanging bodywork and mufflers, and a mere five inches of front-end travel, actually presented Trevor with a different kind of challenge, one which he met with alacrity.
Harris performed his magic in two seperate sessions. So that Dave Kent could accurately gauge and construct the front spoiler, rear panels and fender flares, the car had to be placed at its finished ride height before the torch was lit, so Trevor got hold of the car several months ago to bring it down to earth.
The first step in that process was the substitution of Centerline eight-inch front and nine-inch rear street disc wheels for the stockers. The 14-inch wheels were ordered from Centerline with stock offset specifications so that no additional stresses to any suspension or steering members would be incurred by increased positive offset. These wheels were wrapped with GR50-14 B.F. Goodrich T/A Radial tires on all four corners, to provide a vastly increased footprint over the OEM Mustang tires and to further drop the ride height.
But our IMSA-flavored Mustang needed still more lowering for a real race-car feel, so Trevor went to work at both ends of the car. The stock front coil springs were removed and replaced by a set of custom-wound 180-pound-per-inch coils (at the wheel), setting the car down some 2 1/2 inches in front.
The rear needed substantial lowering as well, so Trevor also replaced the leaf-spring shackle at the rear of the spring with a shackle that he made up for the job. It is 1 1/2 inches shorter, and it lowers the car by about 3/4-inch "for free," as Trevor says. The combination of tires, wheels, front coils and the rear shackle for the leaf springs got the car down to its best compromise ride height. The car was then returned to Dave Kent's shop for completion of all the bodywork.
After the bodywork and paint for the lowered Monroe Handler was completed at CCC, the car went back to Trevor's shop for completion of the total suspension package. The idea was to substitute as few parts as possible, change as few mounting locations as possible, and engineer a kit of pieces that would work on this car as well as on stock or less-modified Mustang II V8 cars. The end result would achieve flat, precise handling in all street driving conditions.
The first modification made to the still-clean underside involved the removal of the factory stabilizer bar and its rubber mounting bushings. Trevor then carefully shaved the exterior surfaces of the bushings fore and aft, and let the stock bore diameter of the rubber. This move allowed the rubber to expand to a tight fit inside the bushing bracket when fitted with a larger Harris Dynamics 1 1/8-inch bar, only 1/8-inch larger than the stock one-inch Mustang bar but twice as stiff. The heat-treated alloy bar was fabricated to use the stock mounting links in their stock locations, but to give the front end of the car vastly increased roll stiffnes and vastly decreased roll angle. "The edge of a very wide, flat tire has very little cornering power," explained Trevor, "so we shot for the goal of keeping as much footprint on the ground as much of the time as possible with the front-end setup."
The Mustang II Cobra II uses a rubber-mounted subframe up front to carry the engine, steering and suspension components and to isolate all of these from the rest of the car for reduced road noise, shock and engine vibrations. Full-on race-car practice would dictate removal of all of these rubber isolator biscuits in favor of hardened steel or aluminum components, affording stiff and solid high-speed handling consistency. But since our project car was designed to be an excellent street car, Trevor left all the rubber components in place and worked with them to gain the goal.
While Trevor opted to keep the rubber pieces, he did pay special attention to the mounts at the trailing ends of each front-end compression rod. This mount was stiffened considerably by the addition of several hardened steel washers between the metal cap and the interior rubber bushing at the trailing end. Compression distance has been increased by 1/8-inch, and Trevor considers 1/4-inch the maximum for street applications. The rear lower control arm bushings were left stock in the final setup, as Trevor considered them plenty stiff. All travel limiters were left stock.
Trevor then left the front suspension for final tuning-in and drove the car about Orange County's fabled South Coast country for evaluation of the rearend and its effect on total handling. Again stressing street performance, Trevor removed the original main leaf, with an extremely flat second leaf, and replaced it, using the already lowered rear spring shackle. During reassembly, Harris substituted some .185-inch nylon seperators between leaves in stock locations to tighten spring action, but quietly. The leaf springs are not symmetrical in relation to the rear axle, with 22 inches from the centerline to spring eye in front and 29 1/2 inches from the centerline to the center of the rear shackle eye. The net result was a rate increase to the leaf spring of over 40 percent, with the leaves still unclamped in either section.
To add further dimension to handling, Trevor is currently working on a 7/8-inch-diameter rear sway bar fo the street Cobra II fleet around the country, based on his work with our Monroe Handler Mustang. Harris chose to stay with the stock Ford 3/4-inch bar, at least until the BFG tires are thoroughly broken in, for street handling.
Shock absorber selection was a multiple-choice process and a project assisted by Monroe's Dick Arend. A variety of shocks were road-tested during the car's first stay at Harris Dynamics, and the choice was the Monroe Handler street series with 45/55 jounce/rebound bias in the front (HP4866) and 50/50 balance on the rear (HP4966).
When the installation was finally completed, Trevor let the Cobra II down off the jackstands for the first time. The exhaust system, the Dave Kent-built exhaust outlets, and the front spoiler all cleared beautifully. However, the tires mounted on Centerline's stock-offset wheels did rub the inner fenderwells near full lock, so Trevor lit the torch and did a minor recontouring job.
According to plans, Trevor Harris will have several more opportunities to retune and continuously refine the suspension underneath the Monroe Handler Mustang Cobra II, because the car's total construction is not yet complete. As front/rear weight biases change with addition of interior and safety items and engine compartment changes, the car will be rebalanced and recalibrated to produce best all-around street ride and handling. And then, from the final version, Harris will be backtracking and engineering several kits for Cobra II street cars in various stages of modification, although everything in the current prototype car will work very well with stock-height, stock-tire Cobras now.
The car's first-generation suspension flog by Trevor Harris demonstrates that the car's handling requires less steering input to initiate car movement, and the car requires less time to accomplish transitions from one input to the next, at any speed.
The last step in stage one of the Handler's suspension was accomplished when the steering settings were dialed in, include one-half degree of negative camber, 2/16-inch-toe-in at a 15-inch checking distance, and three degrees of positive caster, all combining to make the car track straight with little effort and minimal rolling losses. With a slight forward rake, the five-color Cobra II is ready for any street driving situation, with its current powerplant output matched to its suspension.
And speaking of powerplants, we'll return next time with a thorough examination of the breathed-upon V8 engine that will complete the Monroe Handler's major modifications.
Continued from the Horse of a Different Color article.
See the Duke of Windsor article for the final article on the Monroe Handler.
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