Detroit Speed Subframe Connector Kit Install - Project Gets Integrated Rails
We Stiffen Up The Sloppy Steel With DSE Subframe Connectors
From the February, 2010 issue of Chevy High Performance
By Christopher Campbell
Photography by Christopher Campbell
A lot of good things can be said about the evolution from the first to second generation Camaro. For example, the '70-81 cars had vastly improved suspension geometry, larger factory wheelwells, and a more aerodynamic fuselage style body. But one thing definitely not on the list is excellent structural rigidity.
Unlike most unibody designs where the front subframe rails are welded flush to the floorpans in several locations, second-gen Camaro subframes are attached at only four bolt points with body mounts that have a surface area of only a few inches. While there are real advantages to that design, including easy removal and replacement, it also means all the twisting and bending force of suspension travel and uneven road surface is transferred to a small area of thin steel rather than being spread out over a large surface area.
In stock form, soft springs and rubber body bushings squelch a lot of that abuse, but when upgrades like stiff springs, aggressively valved shocks, and solid body bushings are added in pursuit of lateral performance, all that force has to go somewhere. With the stock subframe in place some of the force would dissipate by distorting the weak rails, but with the increased torsional rigidity of our DSE hydroformed front subframe bolted in place with solid aluminum body mounts, most of the force would go into Project F73's sheetmetal. If you had a camera mounted underhood, the flex would be clearly visible.
DSE's subframe connector kit...
DSE's subframe connector kit is a simple looking package with a lot of engineering and testing behind it. They weren't designed to be an easy install; they were designed to be as effective as possible. To help simplify the process, the kit also includes templates, pictures, instructions, and a step-by-step instructional DVD.
While metal fatigue is a real concern, especially from frequent hard driving or track days, the most immediate concern is that deformation and flex will rob our ride quality and cornering potential by altering the geometry of the front suspension and the contact patch of the tire. Not a big deal in a regular street-driven Camaro, we suppose, but who wants to think they're not getting their money's worth out of their new suspension?
What's the solution? It's as simple as a good pair of subframe connectors. The problem is, we need more than a standard set of connectors that hang under the floorpans and bolt or weld to the front and rear subframes. While those do help somewhat, there's only one way to install true subframe connectors-and it involves lots of cutting.
Like other subframe connector designs out there, DSE's design increases the car's stiffness by connecting the front subframe to the rear framerails. Unlike others, DSE's subframe connectors are flush with the subframe assembly, without curves in their shape because the large rectangular steel tubes are integrated into the floorpans. By installing the connectors in this manner they become part of the car, greatly increasing their effectiveness.
It was a solid day's worth of work to prep Project F73, then another to install the rails, but it's time well spent to ensure we're not compromising all of our other efforts to increase lateral grip.
What We Did
Installed Detroit Speed and Engineering's subframe kit for '70-81 Camaros and Firebirds.
We greatly reduced the bend and flex in F73's chassis.
$185 for the kit and it includes an instructional DVD.
The rear subframe is welded...
The rear subframe is welded to the body making it significantly more rigid than the front by installing through-the-floor style connectors. We're essentially extending this strength through the Camaro's tub and permanently attaching it to the front subframe.
Remember the old carpenter's...
Remember the old carpenter's saying here: "measure twice, cut once." We measured a half dozen times and sketched out the area to be cut with a soap stone. This needs to be a precise cut, so take your time and use a sharp cutoff wheel.
Adding the subframe connectors...
Adding the subframe connectors will require you to gut the interior and there's no way around it. To gain full access, part of the cutting has to be completed topside and the connectors need to be welded on both sides. Whatever you don't remove should be covered with a spark-resistant shield to avoid hundreds of tiny pock marks from waves of sparks. (We're planning on replacing that seat anyways.)
Once the offending floorpan...
Once the offending floorpan section is removed you should have a clean cut like this.
Be cautious when cutting out...
Be cautious when cutting out the floorpan; a tight fit will maximize the strength of the installation by retaining as much of the original floor's structure as possible and minimizing the gap needing to be welded. A&E Motorsports got ours incredibly snug all the way around.
Remember how we said stock...
Remember how we said stock Camaro subframe mounts flex the body? When properly placed on A&E's lift, there was 3/16ths of an inch of total flex measured at the front crossmember. A jack was used to split the difference before any final fitting or welding was done.
With the subframe in the hole,...
With the subframe in the hole, F73's stock rear subframe was used to position it vertically in the rear. In the front, the laser-cut DSE bracket that attaches the connector to the front subframe will help show where the connector needs to be located. We clamped the bracket down and made reference marks once everything was in place.
MIG or TIG is acceptable for...
MIG or TIG is acceptable for welding the brackets, but either way, good penetration is a must for the connectors and floorpans to be strong. Lucky for us, A&E's Joe Walden is a master welder with decades of experience. His usual welding machine happened to be on the on the fritz, so he opted to Heliarc everything.
In addition to the side brackets,...
In addition to the side brackets, end caps need to be welded in to box the connectors.
Back under the car, we lined...
Back under the car, we lined up all of our marks and positioned the connector using the stock subframe and the freshly welded bracket as guides. We had a hardy helping of rubberized undercoating to clear away before welding as well.
A wire feed style welder is...
A wire feed style welder is the ideal choice for creating the long final welds to fuse the connectors and floors, but for the initial install Joe continued with the Heliarc. Doing this overhead is much harder, but his welds are still perfect.
This is perhaps the most critical...
This is perhaps the most critical weld for strength in the entire installation process, which anchors the front subframe to the new unibody structure and making the front subframe assembly a permanent fixture. If there's any doubt, now's the time to double check all measurements prior to making this weld.
At the rear of the connector,...
At the rear of the connector, a small gap was cut to make sliding the connector in and out easier during the trial fitment. To increase the strength of this joint, Joe also formed the lip of the stock subframe flush to the body before the final welding.
When it's all said and done,...
When it's all said and done, the whole length of the connector will be welded like this with a wire feed style welder. It can be done with TIG or Heliarc as well-if you've got the patience.
Though they'll definitely...
Though they'll definitely make a bulge in the carpet, DSE designed the connectors not to interfere with the seats or the installation and removal of the rear leaf-spring pocket. Everything will be seam welded from the top side as well for maximum strength.
Now we have a truly rigid...
Now we have a truly rigid second-gen that will dramatically cut down the twist and flex in the chassis during hard cornering. For the ultimate strength, extremely aggressive purpose-built track cars could continue seam welding the stock rear subframe and even use strips of heavy gauge steel to completely box the DSE front subframe to the floors, but this will more than serve our purposes.