Sub Frame Connectors

Getting ready to install sub frame connectors in my 68 Charger. Also going to install front and rear torque box. All parts are from US Car Tool. I wanted to do the sub frame connectors first then do the torque box. Does it make any difference which component is installed first?

yes, sub-frame connectors first, then the boxes. Also, make sure the car is sitting on the suspension/tires at ride height.

Mark

Car sitting on suspension? Then those who make the job on rotisserie?

The fit of the US CarTool connectors is PATHETIC. Slight grinding to fit ... forget it. Get out the plasma cutter !!!

I have no idea what they took the pattern off of but it must have been buckled in half when they did it. There are places with 3/4" gaps - and I'm not talking about small spots - on each side of each rail there's a spot about a foot long that needs trimming up to 3/4".

If I haven't done something with them by July they are going to be presented back to US Cartool at Carlisle !!

That's where the 3/4 inch caulk comes into play.
Never have liked the idea of the thin spot on the rear floor area, kinda defeats the purpose IMO, a full 3 inch all the way for me.

Mine were right on the money...only had a couple of 1/8" gaps. My front floor was replaced by AMD, so maybe US car tool used that as a pattern?

Natcho, if your car is already on a rotisserie, then sure you can always do it that way...most people like me add the connectors and boxes during restoration/mods, and can't afford a rotisserie restoration.

Mark

MIne were done with 3x3 .120 wall steel. I cut them thinner to clear the floor but then welded them back solid so that even though they are thinner toward the rear, they still maintained rigidity. The torque boxes at the rear go over the frame connectors in my car. Not sure if I'd do it that way again since my torque boxes seem to hang lower than I prefer.

In the areas taller than the 3x3 tubing, I welded an extension to give the impression that it was a full depth unit.

I have considered to go back and drill holes that might match the drain holes the factory put in the original rails.

Me neither! But will be installed before assembly K member, axle, engine etc... still on jack stands . They will be regular tubes like the MP ones but will be tricky since is a 74 Charger ( isolated t bar cross member is in the middle ) so will be installed diagonally to sway this piece, just right at the front frame rail junction.

I have an AMD floor section for one side, stock on the other. Even just lying on the shop floor the connector doesn't fit the pan worth a damn !

I've installed two sets so far. I use a small bottle jack to hold the bars up against the floor with jack stands under the rear end and under the frame rails in front of the K-member.

Once I get them to with in 1/4" to 1/3 of an inch, I tack weld them in and massage the floor pan with a big rubber mallet to close up the gaps before welding. I also reversed the polarity on my Mig welder and started the stich welds on the connector and then the floor pan.

Once welded, I sealed the weld with 50 year, paintable roof flashing caulk.

That's the way I wanted to do it. Thanks.

If going to all that trouble with this jacked up and that supported there, don't forget to loosen the torsion bars compleatly. All of the suspension is pulling and pushing the unibody, it'll be hit or miss anyway.

The way I understand it, if the car is all together and someone wants to add these types of reinforcements, they need to be added with the car resting on its tires with the suspension under a load. If the car is suspended with tires hanging, everything sags a little bit. If you weld in connectors and torque boxes then, you may have affected the body gaps, front wheel alignment and drive shaft pinion angle.
The cars on rotisseries have no engine/trans/suspension, axle, steering, so they will not be affected.
The last car that I installed frame connectors was a 71 Road Runner. I used a 2 post lift to raise the car, then I placed tall jackstands under the rear axle and lower control arms to simulate a condition of the car being on its tires. The car had the same body gaps before and after.

Personally I think that whole "sagging" thing is a myth. If its a rotten POS, yeah, it'll probably sag. Otherwise, I seriously have my doubts. But, hey, do it whichever way you feel confident. Have fun welding those in in the 10" space between the shop floor and the floor pan !!

Try opening the doors in a unibody car with it on jack stands.
The engine, radiator, battery and suspension weigh a lot. The front frame rails are designed to resist compression, not extension. When the car is bare, that is 900 or more pounds NOT pulling down on the cantilevered frame rails.
My 70 Charger has no rust anywhere and has never been wrecked but the body gaps did change with it on a 2 post lift. Not a dramatic change but it was enough to cause the doors to drag a bit when opening and closing.

Maybe not sagging, but try to jack a car up by one corner! The car will flex to where you can't get the doors open!

The ride of my '63 Dodge was substantially different after just having subframe connectors installed! I also noticed a difference with the recent 6 point rollbar addition.

I welded the inside and bottom on my 4 post lift, then made some 2x12 plates to raise the tires off the floors by 8". That gave me plenty of space to finish the outside with my tig torch with finger tip control.

Granted, it is a a little tight, but not too bad.

If my frame rail connectors fit as bad as some have stated, I would have fit rectangular tubing, and cut a slot for welding to the floor.

I also bought the torque boxes from Resto Ricks on ebay, as per advice on Moparts...Yes, they are very nice, and are nicer than the the others that I have seen.

Mark

Here are my homemade subframe connectors on the 69 road runner.

Thru the floor is the only true way to do them for maximum chassis rigidity, but most Mopar guys are "afraid" to cut the floor

When cutting the floor do what I did on the Duster, cut 1/2-3/4 inch less than the connector. Use the HF air duck pliers for doing seams, or just vise grips, bend up a lip to allow for connector to be fitted, don't have to be pretty. After connector is installed use a piece of angle iron, clamped to the connector underneath, peen the floor back to the connector, it'll be straight with the angle iron, then tack weld and hammer it down as you move along the cut. No gaps and easy to weld. I'll flip the car over tomorrow and tak some pics, just finished tiging the semi-cage today too.

I like em. I also made my own several years ago before the US car tool ones came out. I didn't like what was offered on the market at the time so I used 2x3 tubular .120 thick steel.

MidPenMopar and 70RT Charger: I wish I had your talent. That's the way to go; make your own. Yours look good. I need a set for my '89 Diplomat Police car with a 410 small block. Although it doesn't seem to flex I'd like to have them. Obviously nobody makes them for this car.

2 X 3 0.120 wall is a really good choice. I don't think you gain much by going heavier or larger. Plus, it's much easier to get good penetration when the pieces being welded are close in thickness.
The last picture looks to be a really clean installation. But, they need paint. Otherwise the job looks half-done.

R.

That looks like undercoating or bed liner to me.

Are you sure he was talking about me lol. Thanks for the compliments. Yeah I think I got the idea from here years ago and yes it is Bedliner.

Opening and closing a 2 door coupe will have noticeable differences in the way the doors close on the striker pins when using axle stands on the frame. The stands aren't that far from the wheels on each end of the car but opening and closing a door, you can see how far out from perfect alignment the car is due to stretching metal when it's hung.

I was talking about the pix from MidPenMopar. The installation looks very good, to me it just needs paint. And bedliner will do the trick too, nice reminder.

R.

Yeah I kind of wished I would have painted mine.Nothing to hide I was just thinking about extra protection at the time.