Chevy II Renovation, Part 2

Completing our Box Nova Heidt's Suspension Transformation

John Nelson Feb 1, 2006 0 Comment(s)

It's been a few months since we began our Chevy II renovation, and the time has finally come to complete this project and put our Heidt's-suspended guinea pig to the test. Our quest to totally transform the launching, handling, and braking abilities of a '66 Nova began with "Chevy II Renovation, Part I" in our Sept. '05 issue. In that first installment we performed "radical bolt-on surgery" by fitting our box Nova with a Heidt's Superide II IFS front subframe. Besides paring 150 pounds off the car's nose, the stout steel box-tubing structure gave us greater strength, as well as rack-and-pinion steering, coilover shocks, and Wilwood four-piston brakes. Most importantly, though, is the fact that the new system provides modern suspension geometry, a necessary update for optimum ride and handling qualities. In this, the second and final part of our Chevy II Renovation, we'll complete the suspension transformation by installing Heidt's Complete Nova Rear Subframe, then hit the test track to measure our improvement.

The Heidt's rear subframe kit includes a top crossmember (or shockbar), subframe connectors, a Panhard bar, coilovers, and four-links with axle brackets. Options include polished four-links and a Panhard bar, chrome coilovers, an adjustable trans mount, and axle housings with the brackets installed. We chose all these options, and Heidt's also sent along a set of 31-spline axles and Wilwood rear disc brakes to complement our front binders. Bolt-in kits are available, but Heidt's recommends the weld-in variety for race cars. Thinking to the future, we chose the weld-in version.

There are many benefits to this setup, strength and stiffness foremost among them. Adding Heidt's box-section steel subframe connectors stiffens the Nova's original stamped-steel flexi-flyer subframe, improving stability and laying the foundation for the improved suspension setup. The stock leaf-spring/shock arrange-ment is replaced with a tunable four-link system and coilovers. Traction, and therefore launching ability, is vastly improved with the four-link setup. "You get a firmer, more solid launch compared to the leaf springs," Gary Heidt told us. "The subframe connectors also have a lot to do with that," he added. We knew the four-link would give us better launches at the strip. But when it comes to making overall improvements to the Nova's ride and handling characteristics, Heidt pointed elsewhere. "The Panhard bar determines the car's roll axis," he explained to us. "When this roll center is low compared to the front of the car," he continued, "you get more understeer, which gives the driver more control. You're then in a nice, drivable car." And that's exactly what we ended up with.

Johns Customz & Performance in Torrance, California, again performed instal-lation duties for this project, and set the veteran Chevy II up for its "after" day at the track. Before we get to that, here's some more info on our particular setup. First of all, we went with BFGoodrich Traction T/A tires, 215/60HR60 all the way around. These tires carry a good "AA" traction rating and a sky-high wear rating of 440. What does it all mean? This is good rubber, but not sticky, canyon carving material, which would have a traction rating in the 300s. In other words, we went with real-world tires that will work well on the street and last awhile. The suspension setup echoed this ideal. Out back, six turns of the spring collars made the Nova's control arms parallel with the ground. Up front, three turns did the trick, while the damping adjustment on the Aldan coilovers was set right in the middle. Rather than using a one-off "track day" setup, we went with a street-going configuration.

The results, as you can see by our measurements, are impressive. We'll take them one by one. First, although the Nova's engine remained untouched, we did stiffen its rear gearing, going with 3.70:1 cogs rather than the old 3.08:1 set. This change, however, certainly doesn't account for a 0.54-second e.t. improvement. The Nova was easier to launch hard, and also tracked much straighter than before, without a hint of fishtailing. Up front, the new rack has none of the vagueness found in the stock steering box. With drag radials in place, we think 13s are within reach.

The improvement in braking was even more impressive. We cut a full 41 feet off our 60-0 mph distance, and fade was virtually eliminated. With g-machine-type rubber, there may have been another 15 feet or so to be had. Besides the great improvement in performance, this Nova's safety factor has been wildly increased. On the skid pad, we again saw a great improvement, picking up a full point and almost pulling .80g. With some suspension adjustment and the aforementioned turn-and-burn rubber, we would have easily broken into this area. The increase in turning ability was borne out on the slalom course, as we picked up a full 5 mph through the cones. More importantly, perhaps, is the improved feel of the car. With its stock suspension (but on the same tires), turning hard was an all-or-nothing proposition: turn hard enough and the back end would slide. With the full Heidt's setup, the Nova gained an entirely new feel. The driver has a "gray area" while turning and can work closer to the tires' edge without worrying about oversteer. And with all that, the ol' Chevy II just plain drives better under normal conditions. Nice.

The bottom line is, we like it when a plan comes together. John Barbera of Johns Customz is very familiar with this car and told us he thinks the improvement is "fantastic." Besides saying the car "handles, goes straight, and is safe," John made one astute observation when he said the driver now "knows where the car is at all times." It's a fitting statement. We've gained performance in all areas, but also control. It's a good place to be in. The Heidt's suspension we installed on this '66 Nova works, and the potential for even greater performance is there. Check out the pics to see how this box finally booked.

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These are the essentials of the Heidt's Nova Rear Subframe for '62-67 Novas. This is a parallel four-link system, which means a Panhard bar is required. Heidt's also sent along a set of its preload-adjustable coilovers, a 9-inch axle housing and axles, and a Wilwood rear disc setup.

Note the contrast between the stock suspension and the Heidt's pieces. Increased strength is a major benefit. The stock upper shock mounts attach to sheetmetal; the new coilovers will mate with a stout tubular shock bar. The four-link setup will locate the new diff much more effectively than the single-leaf springs--and that's not even mentioning the box-section steel subframe connectors.

The stock rear suspension can be removed as a unit, and this is what Johns Customz & Performance did. The strength we mentioned above will be vastly improved by replacing the Nova's original 3.08:1-geared, six-banger-style 10-bolt rearend. Ditching the stock drums in favor of Wilwood discs will also make a big difference.

With the stock suspension out, Johns' Paul Morrow started by test-fitting the forward mounting slot on the subframe connectors. Fit was excellent, but the stock transmission crossmember hinders welding. We supported the tranny and removed the stamped-steel crossmember.

With the original crossmember out of the way, Paul used a wire wheel to clean up the welding area. The rear welding areas get the same treatment. Note the Nova's exhaust system has been removed; the fuel tank has also been set aside to make more working room and as a precaution while welding.

Here's the subframe connector as it will be welded into the Nova. The connectors are constructed from 1/8-inch steel plate and 1/8-inch-wall box tubing. The increase in chassis stiffness is marked.

The rear of the subframe connectors, which incorporates the mounting holes for the four-link setup, slides into place alongside the framerail and front leaf spring mounting bracket. The flimsiness of the original mounting points is evident. Ours were bent from years of duty; clamping them to the subframe's mounting area is a necessity.

On the driver side, the factory parking-brake cable bracket must be cut out to make room for the subframe connector. A new cable system will need to be fabricated.

Unlike the Heidt's front clip, the rear is a weld-in proposition--once a piece is in, it's in. To ensure the Nova, and therefore the subframe connectors, would be reasonably straight once the smoke cleared, Johns carefully measured, car-to-connector, at several points. A side measurement was made at both the front and rear, and the distance from the bottom of the car to the four-link mounting points was also checked.

Johns also checked the car and the subframe connectors with a level. The old Chevy II was remarkably straight, especially given the timeworn sheetmetal structure. Measuring across the rear framerails, our level bubble was almost dead center.

The vertical straightness of the four-link mounting points was also checked. This is critical to prevent any twisting of the four-link system.

Most important of all, however, is the distance between the four-link mounting holes across the car. This dimension must match the one found between the mounting holes on the rearend housing. Ours did.

Satisfied that everything was properly aligned, Johns went ahead and tacked the connectors into place. The Millermatic 271 MIG welder we used made this an easy job.

So far, so good. With the subframe connectors tacked in, the difference between the Nova's thin metal floor and the beefy box-section connectors is evident. The factory trans crossmember was then temporarily reinstalled.

Johns made sure the bar was properly located by measuring from the shock mounting holes down to the lower four-link mounting hole. Again, the distances were a match.

Johns made sure the bar was properly located by measuring from the shock mounting holes down to the lower four-link mounting hole. Again, the distances were a match.

With the mounting groove tabs clamped into place, the shock bar's mounting slots were then tacked to the Nova's framerails.

Here's what our installed shock bar looked like. At this point, there was a lot of final welding to do, as well as a good chunk of under-car painting and cleanup. We didn't stick around for that part...

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