Subframe connectors for a driver/cruiser, necessary to weld to floor?

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hotrod swinger

hotrod swinger

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My 1973 is a driver/cruiser, and I like to smoke the tires now and then, no racing.

Originally a 318 car, now a warmed up 360.

* Update, FYI also has an 8.75 with 355 gears. Auto trans with shift kit.

I'd like to weld in subframe connectors, and I was thinking about fabricating them myself.

I know that ideally the subframe connectors would be welded to the floor, however my undercarriage is coated and I would like to avoid stripping the undercoating, also my interior is fully installed and I don't really want to spend the time removing the seats and carpet.

Is it worth it to simply weld connectors between the subframes without welding to the floor?
 
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I guess it depends on which kind you bought the ones for Mancini just go frame-to-frame others go frame to frame and weld to the floor as well which I would well to the floor if that's the design
 
I was thinking I would buy the steel 2x2 and fabricate them, just welding the ends to the subframes. My question is really whether or not welding to the subframe without welding to the floor makes sense.

I’m honestly not going to remove all of the undercoating and my interior, but I would like to add some strength.
 
The ones that weld to the floor do a much better job at boxing the frames in. The old school ones just use box tube to connect the front and rear sub frames together. It does help but not as much as the ones welded to the floor.
For a mild street car the old school ones are fine. Save your money instead of buying them and make your own from box tube.
 
Try and find a few spots to weld the connectors to the floor where its not going to cause and damage to the interior. Maybe slip a small plate under the carpet and wet it a bit to prevent burning. A few welds
will make the chassis more "unitized".
 
Welding them to the floor is not necessary. And, unless someone shows me an actual structural analysis of the chassis I think that saying one style of connector is better than another is a total guess. I used 1.5"x3" tubing, the benefit to that vs 2x3" is that it stays flush to the floor and the frame rails. With 2x3" it either hangs down further than the frame rails or has to be cut into the floor.

I've installed both the US Cartool style that weld completely to the floor and I've made my own. Making your own out of rectangular tubing is MUCH easier than welding the US Cartool style to the floor, there's no way I'd do that again without putting the car on a rotisserie. And the tubular style do make a significant difference in chassis flex.

Here's my install of the tubular style
My "new" '74 Duster- or why I need a project like a hole in the head

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hotrod swinger said:
I was thinking I would buy the steel 2x2 and fabricate them, just welding the ends to the subframes. My question is really whether or not welding to the subframe without welding to the floor makes sense.

I’m honestly not going to remove all of the undercoating and my interior, but I would like to add some strength.
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I have seen them to the floor, there is still enough flex to cause seperation, seen it happen
 
Daves69 said:
2 X 3 X .125 wall tube used here...........
Weld In Your Own Frame Connectors (archive.org)
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hotrod swinger said:
I was thinking I would buy the steel 2x2 and fabricate them, just welding the ends to the subframes.
Click to expand...

I used the method in the posted link, they work great, I saw a noticeable difference. Fairly easy to do. Just make sure your car is level and secure before you start. Check the doors after it is set and see how they open and close, if happy then have at it.
 
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Mancini connectors. Installed about 20 years ago. Works for me.
They were bolt in style but were welded in.
 
You don’t need any of Them, just keep driving!

A car needs to hook and have some good power before it will need frame connectors. If you have a mild 360 you won’t have too much power, and if radial T/A tires you won’t have much traction on the street.
 
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72bluNblu has given great info here.
I have the tubular original welded mopar performance connectors which have been in the car for over 30 years. Plenty of track passes and tire smoke. They’ll be fine for your application.
 
If I recall there were bolt in connectors available way back when.

FWIW, What the 2" X (vertical) 3" through the rear floor pans will look like this when flush with lowest point of the existing frame.....
upload_2021-12-23_13-47-24.png
 
Make your own or Mancini. I installed a set in a mildly built B-Body. Big difference in handling. You don't need the type that weld to the floor. Not worth the extra work. Good examples by guys who have done it shown above. Do it!!!
 
13 gage 2x3 box layed on their side overlaps the rear framerails nicely. Slot the rear footwell in the floor pan and they stick through about 1/2" relocate that parking brake cable inboard of the connectors too while your at it.

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413 said:
You don’t need any of Them, just keep driving!

A car needs to hook and have some good power before it will need frame connectors. If you have a mild 360 you won’t have too much power, and if radial T/A tires you won’t have much traction on the street.
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Well, I agree if all you are doing is spinning your tires. But if you're hooking up good and your doors won't close and your windshield cracks then you'll know you need em. Then it's too late. I had a V-8 Vega that I learned this from.
 
hotrod swinger said:
I was thinking I would buy the steel 2x2 and fabricate them, just welding the ends to the subframes. My question is really whether or not welding to the subframe without welding to the floor makes sense.

I’m honestly not going to remove all of the undercoating and my interior, but I would like to add some strength.
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That will work very well. I did that 2 x 2 square tube without weld to floor. I drag race the car w slicks and 408 and no harm to body.
 
Scamp Rhonda said:
Well, I agree if all you are doing is spinning your tires. But if you're hooking up good and your doors won't close and your windshield cracks then you'll know you need em. Then it's too late. I had a V-8 Vega that I learned this from.
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Vega? WTH?

Scamps and Darts are much better cars that that junk. With a mild small block and street radials it’s not needed. How many thousands of A body mopars are out there without them?
 
moparmat2000 said:
13 gage 2x3 box layed on their side overlaps the rear framerails nicely. Slot the rear footwell in the floor pan and they stick through about 1/2" relocate that parking brake cable inboard of the connectors too while your at it.

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Really nice job and great pictorial of the process. Thanks!
 
413 said:
You don’t need any of Them, just keep driving!

A car needs to hook and have some good power before it will need frame connectors. If you have a mild 360 you won’t have too much power, and if radial T/A tires you won’t have much traction on the street.
Click to expand...

413 said:
Vega? WTH?

Scamps and Darts are much better cars that that junk. With a mild small block and street radials it’s not needed. How many thousands of A body mopars are out there without them?
Click to expand...

I wholeheartedly disagree, even mild street going cars will benefit from subframe connectors. The may not be "mandatory", but the improvements they offer can be noticed even with a mild street car.

I know that because before I installed my subframe connectors I was just running a tired 318/auto and 225/60/15's. After I installed them I went to a 400+ hp 340 with a 4 speed. The chassis was stiffer, despite the upgrade in power, then it was before.

And you have to consider what the factory design was intended for. The chassis wasn't even engineered for radial tires, they were designed and left the factory with bias ply's. So while I may poke fun at the "hockey puck" hard BFG T/A radials, they're still a BIG improvement over the factory tires. Which means more traction and more flex than what the factory intended.

And the other thing people overlook is this, the factory doesn't as a rule do what's "best". Sure, there are great engineers involved, but there are also bean counters involved. In most cases, you can count on the factory to do the cheapest thing that they think will sell and won't run afoul of any regulations. So just because the factory sent these cars out without subframe connectors doesn't mean they aren't better with them installed. Remember, these things were supposed to last ten years and then get tossed.
 
hotrod swinger said:
My 1973 is a driver/cruiser, and I like to smoke the tires now and then, no racing.

Originally a 318 car, now a warmed up 360.

I'd like to weld in subframe connectors, and I was thinking about fabricating them myself.

I know that ideally the subframe connectors would be welded to the floor, however my undercarriage is coated and I would like to avoid stripping the undercoating, also my interior is fully installed and I don't really want to spend the time removing the seats and carpet.

Is it worth it to simply weld connectors between the subframes without welding to the floor?
Click to expand...
Unless you have slicks and are racing you don't need subframe connectors. It's only the force of power against traction that generates the need for connectors to reduce body twist. If you dont have north of 450 hp and slicks/traction save your money.
 
Oldiron440 said:
Unless you have slicks and are racing you don't need subframe connectors. It's only the force of power against traction that generates the need for connectors to reduce body twist. If you dont have north of 450 hp and slicks/traction save your money.
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Wrongo. If you set the car up with bigger sway bars, wider stickier rubber, and poly bushings, it will most certainly benefit from subframe connectors keeping the body stiff and forcing that upgraded suspension to do its job. Not everything about these cars involves just a straight line.
 
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