I finished the installation of sub-frame connectors on my 69 Camaro. While I installed them I also put in some new sub frame bushings. Both came from Detroit Speed & Engineering. Installing these SFC’s is a lot more involved then your standard SFC install on a late model Camaro. The way these are design they are virtually invisible when looking at the side of the car, unlike bolt in ones which hang about 5 inches from the bottom of the car, these follow the contour of the floor pan allowing them to be very low profile. Here’s the write up:
The first item I installed was the sub frame bushings. As some of you may know the first and second generation f-body’s came with a removable front sub frame. The car was a sort of hybrid uni-body. The front sub frame is held in with four body mounts and two that attach to the radiator core support. Here’s the kit from DS&E.
The bushing in the center is for the radiator core support the other two are the body mounts. The new ones are made of aluminum and are hard coated. They came with stainless steel washers.
Here’s a side by side with the old polyurethane bushings.
I never drove the car with the original rubber sub frame bushings, so I can’t really tell you how the new ones compare. I was hesitant to switch to solid aluminum bushings fearing that solid bushing would destroy the ride quality, but it did not change at all from the poly bushings. The main reason I went to aluminum bushings is that when you add weld in SFC’s there can not be any flexing in the front sub frame, the flex caused by rubber bushings would put stress on the welds connecting the SFC to the sub frame and likely cause the weld to fail over time.
To install them I loosened all the bolts on one side of the sub frame, and then used a pry bar to help lower the sub frame a little bit, I then repeated the same procedure on the other side. By installing one side at a time I was able to keep the front subframe aligned. The four body bolts were torqued to 80 ft/lbs the fronts to 35 ft/lbs. This is the rear bushings installed.
You’ll probably notice I don’t have grade eight bolts for these. I needed longer bolts for the new bushings and Home Depot did not have the size I needed (3/4″ x 3 3/4″) in grade eight. I’ll replace them with better one as soon as I can find them.
For the fronts I was able to find the proper bolts, here they are installed.
Before I started the SFC install I made sure that the front sub frame was aligned properly with the rear. This is critical, because as you can probably guess if the front sub frame is out of alignment it will be locked in place when you weld in the SFC’s. The GM service manual I have outlines the whole procedure. Basically there are some alignment holes on the front sub frame and on the rear frame rails (which can be seen later on in some picture). With the car level you string a plum bob from the center of these holes and measure diagonally. The two measurements were off by less than a 1/16″, which corresponds to what the alignment guy told me when it was aligned.
After disconnecting the battery, ignition system, and fuel/brake lines I started tearing apart the interior. First to go was the front seats, they are held in with four 1/2″ bolts each.
Then the rear seat, the bottom comes out by forcing your knee up against the front part of it to unhook from the floor. The seat back comes out by simply pulling it up.
Next out is the rear carpet section; this comes out by loosening the sill plates and a bolt at the end of the center console, which is hidden under the ash tray.
The old asphalt sound deadening is the next thing to come out.
This is why people in the north hate us southerners. 36 years old and the floor boards are solid as a rock.
In my haste to install the connectors I forgot to take a picture of them before I began the install. Here’s a photo from another site
(Photo credit: Scott at http://www.lateral-g.net)
This type of connector is installed by cutting a slot into the floor pan through which the connector is slid, this is how the connectors are able to maintain such high ground clearance. Templates for all the cuts are provided by DS&E.
The template is placed on the underside of the car. Using magnets to help hold up the template is a big help. The template it located using the rear edge of the front sub frame and the pinch weld by the rocker panel.
I originally used dykem blue and a scribe to transfer the lines onto the sheet metal. However, because the bottom of the car was painted black the scribed line did not show up very well. I traced over the line with a yellow paint pen.
Next a section of the seat riser must be cut to gain access to one of the joints that needs welding, again a template is provided and is located using two of the seat bolts.
Here the seat riser has been cut and the floor pan has been partially cut. There are also two spot welds that need to be drilled out.
All the cuts have been made. The exact same procedure is repeated on the other side with the same template.
Now every install is not complete with out an unforeseen obstacle. Mine came in the form of a crushed rear frame rail. This is most likely due to improper jacking technique by a previous owner.
This is an issue because the rear part of the sub frame connector welds to this part of the rear frame rail. With the SFC dry fitted it was clear that the part of the rail that would normally meet with the back edge of the SFC was way below the edge of it. The gap, which should normally be about 1/16″, was about 1/2″. This is the main part were the SFC attaches to the rear frame rail, and I wasn’t about to try to fill in that gap with globs of weld. My first idea was to use an auto body stud welder. This however did not work, the rear frame rail is about 1/8″ thick and the slide hammer simply slipped off the stud. I tried heating the metal and then pulling on it but the slide hammer still slipped off the stud
The only way the indentation could be removed would be by hitting it from the opposite side. I saw that the spot I needed to hit was just on the other side of some sheet metal on the inside. An access panel was made:
I discovered that after my initial cut there was another piece of sheet metal between me and the frame. I used a pneumatic body saw to cut the inner piece of sheet metal. This allowed me to fit a 1/2″ extension through the cut and pop the indentation out.
Here you can see that the fit it much better then before.
Now that that problem has been solved we can move on to preparing the SFC’s. First they have to be dry fit and cut to length. I cut them so that there was about 1/2″ in-between the edge of the connector and front sub frame.
Next an end cap in welded on to seal the end.
After that the connector is put back on the car and the side brackets are place up against the side of the connector, when welded these connect the front sub frame to the SFC. The design of the SFC does not allow you to weld around the full perimeter of the bracket, the floor pan gets in the way. So you have to tack the bracket in place and then remove them from the car. Now you can weld all the way around
Plug welds are also done on each side
I welded along the under side of the connector too, welding one inch at a time and switching sides to minimize distortion.
The access panel is welded back in place and ground smooth.
The flap I cut to get to the back of the rear frame rail was also welded back up.
I then hit the entire area with a coat of epoxy chassis paint
The last thing to do is reinstall the drain plugs with some seam sealer and put the interior back together.
Your inferior bolts are insulting.
Seeing as how this was originally written about 6 years ago I think it will be fine. Although I will probably upgrade them when we swap the engine out.