Subframe Connectors & Rotisserie



When I purchased this car the original owner said it felt a little "soft" and he recommended I not drive it till the floors were repaired. Overall good advice however, this is a 54 year old unibody and its been driven for God knows how long with weakened floors. This can cause metal fatigue on other structural members making the unibody even weaker. Now I'm not going racing but this weakness problem can be overcome by installing a set of subframe connectors which will essentially turn this car structurally into a full frame unit.

A bit of searching on the web will find several options for subframe connectors ranging in cost from $160 up to several hundred dollars, depending on the manufacturer and the "ease of installation".

Here is one option which is laser cut to fit the floor, however it requires a LOT of welding to install. Cost on this one is around $190.



Another option although not as inexpensive are these bolt in units from MagnumForce. They run around $350.



Or, if you're cheap like me $28 worth of .120 wall 2"x 4" rectangular steel tubing will do the exact same thing. Installation is a little more complicated but still pretty easy.

The reason to use this 2"x 4" tubing is simple. It will fit nicely inside the rear frame rails and it will basically serve to extend the rear frame rails up to the torsion bar crossmember completing the full frame unit.

I'm not going to go into excruciating detail on how these are installed but I will cover the essentials. Basically the rear frame rails are cut so that the tubing will slide inside and the tubing is cut to allow at least 2"-4" to slide into the rear frame and also to butt to the torsion bar crossmember. On this car that length is 52".

In order to fit these bars a channel needs to be cut in the rear floor. This section of the floor sits lower than the rest and will interfere with the new subframe connector so a channel needs to be cut to allow the 2"x 4" tubing to run straight up to the torsion bar crossmember. This is no big deal but it must be carefully marked and cut since the floor will need to be welded to the subframe connector to restore its strength and you don't want too large of a gap. Here is a completed subframe connector where it runs through the rear floor.



And both sides complete. You can easily see why this section of floor must be channeled in this pic.



Underneath the car the installation is a bit simpler. Its just a matter of welding the tubing to the rear frame and to the torsion bar crossmember. If I was going racing I would have used a piece of 1/8" plate to add some extra strength to the but joint at the torsion bar crossmember but if you remember from the pictures of the front floor when it was opened there is an internal brace in that same location so for a street car no extra plate is really needed. Here is a shot that shows how the tubing is inserted into the rear frame rail and then welded in place.



And the front section where it butts into the torsion bar crossmember. I'm not a professional welder so most of my welds need to be dressed. In this case I'll dress out these welds when I get the car up on a rotisserie. I'm to old to be doing that kind of stuff laying on concrete under a car. Welding them in was bad enough.



Here's a compound pic showing both subframe connectors in place.



With the floors done and the subframe connectors installed its time to get this body up on a rotisserie. Unfortunately I don't have one and I'm not willing to spend $2000 for a tool I'll use once or twice, so I'll build one.

The easiest way to do this is to modify a couple engine stands, however since I want to add some of the features that some of the commercially available units have, the modifications will be substantial. I used Harbor Freight engine stands because they just happened to be on sale and my total investment including the steel is just over $200.

Once again I'm not going to go into detail on how everything was done, but I will show several pictures and do my best to describe the basics of how it was built.

As you can see there isn't much left of the original engine stand. Basically just the base and casters. One thing to mention here is that all the joints where these inexpensive engine stands bolt together are welded to increase strength. The tubing is 2.5" over 2". You can see the pad for a bottle jack which allows the whole unit to be raised in order to get the center of gravity high enough for the body to clear when its rotated.



Here is a look at the bottle jack and how it will work. Most of the commercially available units use much larger jacking units but I'm cheap and I just happened to have this bottle jack so it will do.



This screw jack assembly is used to adjust the center of gravity once the body is mounted. This adjustment makes rotation of the body easy. Without it rotating the body can be a real pain... both figuratively and literally.



Both rotational ends are connected with a 1.5' square tubing to keep everything aligned and basically the rotisserie is complete.



With the use of the engine stands and the other adjustments built in this unit should be pretty useful. It is NOT designed or built to be a heavy duty commercial unit, but the tubing is thick enough to easily handle a 1000 pound body.

Next I'll start the dissassembly of the suspension systems, remove the doors and get this thing mounted on the rotisserie. Then the fun starts.

Check back often for more updates...





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