By Rotten Rodney Bauman
Since Street Tech magazine is an honest publication, let’s begin this story with honesty. Like other serial freelancers, yours truly has geographically-convenient favorite places to sniff around for tech. Outside of our own home-based hobby shop, Hot Rods & Custom Stuff (HR&CS) in Escondido, California is only 14 miles (that’s about an hour) away. HR&CS is a big shop with plenty goin’ on, so apart from the rugged commute, it’s easy-pickin’s for tech. On a typical visit I just happened to catch the beginnings of the following work-in-progress. At the time of this typewriting, a 1970 Z-28 is in the care and custody of HR&CS’s fabrication department for substantial stiffening of its underdeveloped understructure.
From the assembly line, like the generation before, the second-gen F-bodies lacked the structural integrity to withstand the torque of big horsepower and/or the twisting forces of competition like drag racing, autocross, etc. Today we’re fortunate to have a solidifying solution, packaged in convenient kit form and developed specifically for a number of individual automotive applications—subframe connectors from Detroit Speed & Engineering.
As a Detroit Speed dealer, HR&CS can provide the product, as well as install complete kits in just under a jiffy. Even those who are crafty enough to handle their own first-time subframe connector upgrade would do well to at least take a tip or two from a HR&CS fabricator who does these jobs routinely. That said, we’d recommend the use of a bookmarker here.
The following structural upgrade begins with a plumb bob, after the installation of new rubber body bushings, or better yet for maximum stiffness, Detroit Speed’s own billet aluminum body mounts. It’s crucial that the body and subframe be properly aligned before fab work begins. On this particular car, the alignment was completed prior to this writer-shooter’s tardy arrival, but the body-to-subframe alignment procedure is covered in the kit’s instructions. From here let’s move a little closer to the bottom side of the car and see what’s really involved.
Here’s what’s supplied from Detroit Speed: left and right subframe connectors, inside and outside brackets, end caps, templates, installation DVD, and detailed printed instructions.
HR&CS fabricator Jeremy has already seen the movie, read the instructions and installed a good number of these kits before, so this job will move along quickly. Before the sparks begin to fly, it seems worth mentioning that caution should be taken to protect the car’s glass. How many of us have learned this the hard way?
In this instance, previous damage to the car’s floor is clearly visible. These small dented areas are best hammered and dollied before any cutting of the floor begins.
According to the instructions, measurements should begin at the rocker panel pinch welds. Providing the car has not been damaged; or worse yet; damaged and previously repaired in these areas, the recommended procedure is the way to go. This car is no virgin, so Jeremy double-checks using his own alternative measuring points.
With the supplied templates now trimmed from the instructions, Jeremy has opted to transfer the shapes to poster board. The slightly thicker material will be easier to trace an outline around.
For the revised template’s final trim, this pair of professional-grade ambidextrous template scissors is the hot-tip-tool for the job.
As long as the bottom side of the car’s floor is clean and dry, a dull Sharpie makes an adequate scribe.
Now in addition to the paper protection for the car’s glass and remaining interior trim, a “tent” has been fashioned from random 2-by-4 remnants and a welding blanket. Since the first cuts will be to the bottom side of the floor, this ounce of prevention makes for good fire insurance.
Once satisfied with the accuracy of his markings and prior-to-cutting preparations, Jeremy lets ‘er rip with a cutoff-disc-equipped angle die grinder.
Certain slices are best made from the topside. For these cuts we must break camp and remove the tent. But from this view, at least we can see that stray sparks are controlled.
With a rewarding “clang,” the first-fallen section meets diamond plate and concrete. Granted, that’s not very technical, but we truly enjoy the sound it makes—and we think the picture is nice, too.
Here Jeremy makes a little fine-tuning adjustment to one of his initial cuts. For this, a Central Pneumatic high speed metal saw from Harbor Freight is absolutely invaluable—and it lends good contrast to his box of otherwise Snap-on tools.
As supplied, the subframe connectors are a tad too long at each end. With the unwanted floor sections trimmed free, the subframe connectors are measured and trimmed to match. The slot at the rear of this subframe connector will require a slight bit of relief, but for a first fit, this isn’t bad at all.
The fit is a close one, and tight in one place. With a gentle tap of the mallet, it slides in firmly enough to stay.
Although the fit is satisfactory, it’s temporary at this time. The supplied brackets are not yet attached and there’s still some preparatory work to be done to the floor.
Rubberized undercoating can be stubborn, and wouldn’t you know it; this car has it on both sides of the floor. This type of material goes gooey when abraded, but after a while, it gives up and goes away.
So here’s a topside view of our fit-check. From here the subframe connector will assume a position on the welding table for further fabrication.
The supplied end caps are the “cock for Dolly” just as they are. These are thoughtfully stamped just slightly smaller than the rectangular-tube subframe connector’s outer edges. A pretty little TIG weld will fill the recess nicely.
For the TIG-welding tasks at hand, the shop’s Miller Syncrowave 200 is Jeremy’s machine of choice.
Jeremy has decided to make a quick cleanup pass over his end cap welds, but only where brackets will go. This is only to clean the metal in preparation for the next pretty little TIG welds.
With the end caps now finished, the subframe connector is supported in position as it will be. Now the inner and outer brackets can be located and tack-welded to the subframe connector. For this, the shop’s Millermatic 135 MIG welder is Jeremy’s little buddy.
Back at the bench once again, the subframe connector is ready to have its brackets TIG welded for keeps.
So far it’s been a day chock-full-of miggin’ and tiggin’. Miller MIG—Miller TIG—must be Miller time.
With the TIG-welding of the brackets now finalized, the subframe connector is in position and about to become a permanent stiffening member.
Of course, fire-preventative measures have been taken. Since we can’t see what’s goin’ on inside the car while MIG-welding down below it, Jeremy has pitched his welding blanket tent as we’ve seen before—just prior to pullin’ the trigger.
As we’re nearing the homestretch, the topside joints are MIG-welded as well.
When these procedures have been completed on both sides, the beefed-up areas will be chemically-cleaned and primed. The rubberized undercoating will be matched and spot-repaired. From there this ol’ car will be driven—hard. How do you drive yours? Perhaps you should consider a Detroit Speed subframe connector upgrade, too.
Detroit Speed & Engineering
Hot Rods and Custom Stuff