Wondering about subframe connectors

[Mopartist]

I was looking through the "tech" pages concerning subframe connectors and it seems there are two ways to go on these (unless I'm not seeing it correctly) First off; some guys build their own out of square tubing and "wrap" the rear frame; while "butting" the front crossmember while keeping the whole connector hanging just below the floorpan. On the other hand; some guys trim along the length of the connector to follow the contour of the floor pans, or cut a channel in the floorpan for the connector to slip through. Then weld the entire length to attach the floor to the connector. Is there much difference between the two schools of thought as far as performance? The first seems like a lot less work; but is it not as strong?

Also; the tech article states 2 X 6 X .125 mild steel for the forward, and 2 X 3  X .125 for the rear. Is that correct?

[Capt Jack]

I do believe the 'through the floorpan' version is indeed stronger and more effective against chassis flex and twisting.  my thoughts would be the cut the floorpan version would be a far better choice for higher HP applications where the stiffness of the chassis (as well as cage mouting points) is of a higher importance than a more street oriented version. 

currently I have the straight bolt-on versions which, while not nearly as effective as welded, are far better than nothing at all.  eventually, they'll be welded in, but at the moment its what I have.

[kawazuki8097]

I picked up a set of MP bolt-ins for the convert. I am going to locate them with the bolts, then weld them in.  Everyone said "build - don't buy". They were right! The $$ I spend on the connectors would have bought me enough tubing to do both the convert and the 73 with a few bucks left over. From what you have done on the car so far, you could easiy build a set of these for the car. You will get diff answers on the tube dims depending upon who you ask. The chassis guys say 2x3 going through the floor is best and to set the tubing with the 3" portion going up and down, not side to side, as it will be stronger. 

[440+6Scamp]

Here's another option:  I slide a 2x3x.125 rail inside the rear frame rail by cutting into the floorpan and cutting off the front face of the rear frame rail.  The rails pertrude into to the floorpan about 2" but it's only in the floorboard of the rear seat.  Should be plentry strong.  Here's a few pics.

[440+6Scamp]

And 2 more:

[Womanator]

I put the Mopar bolt in conectors in the 67 Dart and then welded them in car goe's 11.16 no stress cracks yet

[b569rr]

Ken; That 2" x 6" x 1/8" is for the flat bar and the 2" x 3" is the tube. There must be 100 topics on this and there are several great ideas. Alot of people position the 3" vertically for more strength.

I did mine per the tech pages and they stick through the floor no more than a half an inch. I can jack up the car anywhere on the tubes and the car is very rigid.

Make sure you put a 4.5" wire wheel on your 4.5" angle grinder to the steel to be welded. IMO this is the easiest way to prep the steel prior to welding. I can post a pic of it if you need.

Here's a few things to help that I found out.

Cut your connectors so they come within 1/2" to your spring boxes that I see you are using. This way you can get a nice weld to your subframe.

When its time to cut through the floors, place the connector near its final position and use screw or bottle jacks to press the tube against the floor. Use a scribe to mark the floor. My favorite tool it the 4.5" grinder wheel x .045 " thick. Plasma's are great but leave the final fit with gaps. Sawzall's are great but too agressive. A 4.5" wheel lets you cut like a surgeon and the wheel acts as a straightedge. As for the length of the penetrations, stop short when cutting, place the tube back under the car with the jacks and test fit. You can always cut out more material if needed. I think I had three test fits. Tack the hell out of it.

For welding, keep most of your puddle on the tube and walk it over to tie in the sheetmetal. This will require a side to side motion. Imagine a tight zig tag motion. Develope a 1, 2  3 rythum in your head with a duration of 2 seconds each cycle. 1, 2 on the tube and 3 on the sheetmetal. 1, 2 on the tube and 3 on the sheetmetal.
If welding from below turn your gas up to 25 CFH as Argon is heavier than air and wants to sink. Keep your nozzle clean.

You are making a structural weld so use a push method. Point your gun slightly away from the direction of travel back towards the puddle. Focus on the puddle not the wire. You are dragging the puddle from tube to sheetmetal, not the wire.

Sorry for the long post. Just trying to help a newbie to welding. And thanks to Bill for the information in the tech pages.

[robx4406]

Nice post b569rr   

My 2 cents

When you are welding, set the welder to weld the THINNEST material. You are going from 1/8" (.125)  or roughly 3/32" (.090) connectors to roughly 18-20 Gauge or so sheet metal floor.  Set the welder for the 18-20 gauge, NOT THE 1/8"  You'll be blowing hole in the sheetmetal so fast your head will spin.  I'd weld as much as you can from the top side, easier, hit it quick from the bottom if necessary.  Finish it up with some seam sealer/silicone.

Watch out for undercoating dust if you are cleaning the bottom side of an undercoated car.  Stuff may have asbestos in it and will cause a nasty rash  on some people.  Cover up real good when cleaning and wear a respirator 

Mopartist,  still working on getting the traction stuff together.

 

[Mopartist]

Here's another option:  I slide a 2x3x.125 rail inside the rear frame rail by cutting into the floorpan and cutting off the front face of the rear frame rail.  The rails pertrude into to the floorpan about 2" but it's only in the floorboard of the rear seat.  Should be plentry strong.  Here's a few pics.

Wow! This is REALLY innovative! I may go with this method as the tubing is mounted "tall" instead of "wide". How did you attach them inside the rear frame tube?

TOM & ROB -- Hey; don't worry about the long post. I can use as much help from you guys as you can give. If it comes in two cent increments; I'll take a 100 bucks worth!   It's MUCH appreciated!

ROB- No hurry on the traction bars; I don't have a motor yet! 

[440+6Scamp]

There's about a 10" overlap where the 2x3 is slide into the rear subframe.  Before sliding the tube in, I drilled several 1 1/2" holes along the overlaped section and rosette welded the tube in.  I also welded around the end of the rear subframe and along the floorpan.  Hopefully this picture will clear it up:

[abqdart]

I did it the "otherway" and I am changing it to the 2x3. You can see the flex in the 1x3 over time. Its still strong and it works on street cars but take the time and do the 2x3. I think you will be happier. I say this because, again, I am changing to that style.

[64dartsb]

good post this is helping me a lot...  The more pictures the better.  I am going to be doing this within the next month to my car, I'll try to get some pictures of it on here.

[67bcuda]

I made my own according to the tech page and was absolutly amazed at the difference in the way the car felt.  You dont realise how much your car flexes until you stop it

[JohnnyfromChicago]

440-6 I love the through the frame and floor idea - I thing thats the best idea I've ever seen for these.

[ab7fh]

When installing subframe connectors, where is the best place to support the car from? I don't want to weld a twist into the car, when installing the connectors. Supporting the car by it's wheels isn't an option at this time.

I really like 440+6Scamp's connectors. Great job.

[zpsull01]

When installing subframe connectors, where is the best place to support the car from? I don't want to weld a twist into the car, when installing the connectors. Supporting the car by it's wheels isn't an option at this time.

I really like 440+6Scamp's connectors. Great job.

I'm in this same situation at the moment. The car is currently stripped all the way down to the shell and is rolling around on a cart that I built out of 4x4s with casters that accommodates the subframes. We have a 2 post lift here at the house but should I install them while it is in the air or what? What is the proper way to do this?

[69 GTS Clonvertible]

Here are the instructions I got with my sub-frame connectors from MP.

[zpsull01]

That helps some but my car is just a shell now. No suspension at all. What do in this case?

[*DB*]

If your K-frame is still in, I'd put one jack stand under the center of it & 2 under the rear frame rails near the front spring mount area.

[zpsull01]

Would there be any way that I could use the lift for the installation? I really would like to make this an easier overhead installation.

[abqdart]

Well bringing back an old post. Went and got the stock today 2 x 3 x .125 and doing my "new" subframe connectors. I also am going to start my Cal-Trac experiment. Did some snooping around this week and scored some major stuff for dirt cheap. (thanks Mopowers for the inspiration) Anyway, I have ALL my fuel line -8 Braided SS and AN fittings getting here next week. I need to Fab up these new frame connectors and Cal-Tracs , run some brake lines and wire the car. Count down begins. I predict that by April 20 my Dart will be running. After 10 long pain in the ass years she will be running and hopefully driving. I have Six-Pack performance picking up a 6pak hood from Mopars at the Strip and I will need a new right quarter and the valance panels but I will get them from AAR or someplace that has them in fibreglass. wish me luck yall

[smallbigblock]

Ten years is a long time ...you must be excited.  I still have no end in site for mine. 

My 2 X 3 X .120 tube is sitting on the garage floor now.  I got to do a couple more thing first but it's coming soon.  Keep the pic's coming.

Good luck

[wedgie]

I did the subframe connectors for both my cars while on a chassis lift. I did support the rear of the frame with two adjustable supports and one under the center of the K member. I did this to make sure there was no sagging. It is easy to tell. If your doors fit well while on the suspension, you need to make sure that they operate well when on the lift. On my Coronet, I used 2X2 tibing because I didn't want to cut the floor. I used 2X3 on the Dart through the floor. It is amazing how much more rigid the Dart is than the Coronet.

[satellite65]

I like the ones made by U.S. Car Tool (also sold by Magnum H.P.) They're laser cut to fit the floorpan and get welded the entire way through. has anybody used these yet?  I'm still waiting for them to make the ones for early B-Body. So far, they only have '66 and up. Plenty of A-Body stuff though. Check it out.

http://www.magnumhp.com/

http://www.uscartool.com/

Steve

[Bakaruda]

I used 2X3 and put them over the rear frame rails.

[74swinger]

I did mine as per the tech pages.  I think that Bill really got it right.

When it came time to support my car, I had no motor, tranny or rearend in the car.  Put my stands under the K-frame and a couple of sets u nder the rear frame rails (six stands in total).  I agree with the other posts, if you watch the gaps in your doors, and open and close them with no change in gap, the car is not sagging.

The primary goal of the frame connector is to stop the twisting of the car.  Don't loose any sleep over the sag, it easyt to adjust body panels if you are really fussing over the gaps with a micrometer.

By the B69RR, you can write for days, and I guarentee I will read every word.  You do some amazing work, and you really know your stuff.  Any advice from you will bee gladly accepted by most if not all on .   

[PureGTS]

MY RR has the subframe connectors done through the floor and in to the front of the rear subframe in 2x3. I got lucky and had the springs moved, subframe conn's put in along with tubs for $600. I wish the guy who did it was still around (moved). However, my Dart is out getting the other treatment (not through the floor), even as we speak, as it is not a track car but a street car with handling plans, not drag racing plans.

[4spdfury]

we always set the welder up for the .125 wall not the sheet metal. if you do it the way tom describes you wont blow through the sheet metal.