It’s cool to drive a vehicle that requires both arms and the strength of Schwarzenegger to turn a corner. The suspension has more ups and downs than the current economy, and it’s a battle just to keep the car in one lane as you drive down the road. It’s cool, that is, for about the first week. Then a combination of fatigue and concern for safety takes over and suggests that maybe the 30-plus-year-old chassis needs an update.
If your car or truck has an independent front suspension, a complete rebuild using stock replacement parts will probably make its ride and turning ability a little more livable. But that won’t decrease steering and brake effort, and you will still have ancient suspension geometry. Straight-axle-equipped vehicles are even worse. If enjoyment in driving your classic is the primary concern, then a front subframe installation can be the best solution. Grafting a later front clip onto an early chassis replaces outdated suspension components to give your classic chassis better geometry for better road control and driving comfort. A later subframe will also add disc brakes and a relatively new power steering system.
Such swaps aren’t best for all vehicles, but a swap should be considered for straight-axle vehicles for which independent front suspension (IFS) kits are not available and for pre-’64 GM cars that have outdated IFS, steering and brake systems.
This type of swap is complex and requires skills and tools typical of a frame or chassis shop, since it means whacking the stock frame in half and mounting a new front half under the vehicle. Positioning is critical for proper driving characteristics and so all the other original components of the car or truck work with its new front suspension.
Before you start cutting your old chassis, consider which subframe would be a good candidate to swap under your car or truck. You’ll need to find something with a similar track width (measured from wheel mounting flange to flange). The donor suspension should also use common pieces that can easily be found in salvage yards and for which you can get replacement parts. One option for mid-’50s trucks and ’30s-’40s fat-fendered vehicles is to use mid-’70s Mopar front suspensions. That front suspension uses torsion bars and makes height adjustment quick and easy once the suspension is installed. However, the torsion-bar mounts can create problems with the exhaust system and transmission mount.
The ’67-’69 Camaro and ’68-’74 Nova subframes are popular because they offer a slightly narrower track width than the later ’70-’81 Camaro and ’75-’79 Nova subframes, but they are becoming harder to find, can be more expensive, usually require a disc-brake swap, and the steering box is mounted behind the crossmember, which can make steering-shaft fabrication difficult. That makes the later GM F- and X-car subframes an attractive alternative. Those subframes are inexpensive in salvage yards, come with disc brakes, and the steering box is in front of the crossmember. Memory Lane Collector Car Dismantler, a Southern California salvage yard that specializes in pre-’74 American automobiles, sells the ’70-’81 Camaro and Firebird subframes with the power-steering box, the sway bar, the brake rotors, the calipers and the complete front suspension for about $350, depending on condition and supply. You can barely buy a front-disc-brake conversion kit for most cars at that price, so a subframe swap makes sense.
We took a ’57 Bel Air to Precision Alignment to illustrate the procedure of grafting a subframe to an original frame. The shoebox Chevy cars’ front suspension can be rebuilt and upgraded to drive better, but the expense of rebuilding the suspension, adding disc brakes, adding a sway bar, upgrading the steering box to a modern one and replacing the motor-mount system with side mounts and a crossmember can easily add up to the total cost of a Camaro/Nova subframe and its installation by a professional. And, after doing all those upgrades to the stock suspension, you still have a suspension design that is over 30 years old and has been crutched to work better. Furthermore, the frame on our car had damage on the passenger’s side, which would make it difficult to restore. This front-clip installation is even more desirable on straight-axle vehicles such as ’59-and-earlier GM trucks and the popular ’53-’56 F-100 Ford trucks.
The most critical part of grafting a new front clip onto an old chassis is measuring and positioning, so we will deal only with preparing to chop the original frame in two in this article (Click Here To View Part II).
