Trying to decide on subframe connectors

[Dreamcar]

I'm trying to decide what type of subframe connectors I want. I'm debating on the contoured connectors or using the bolt-in connectors that I can then weld in.

First, here's where the car is at: Leveled on 8 points on jackstands, doors installed and working, no engine, no trans, no suspension, no diff, no interior, and no quarter panels. She's been stripped bare so there's no excess weight hanging anywhere.

If I go with the connectors that follow the contours of the floor, I'll obviously have to install my new AMD floor pan first because the factory floor is rotten. This means the connectors will have to be installed when I'm on my back and the car is on stands. And, they'll be matted to a non-stock floor pan so there'll likely be more trimming to do. However, I agree they look nice and almost stock once installed.

If I go with the bolt-ins, I can installed them (bolt-in first, then weld) without the floor pan being in, thus making the job much easier. And, if I use ones like those from Competition Engineering, they bolt through the front cross-member and once welded, will be attached on both sides of the cross member and not just on the back side. They are usually less expensive, but I know they don't look as nice as the contoured connectors.

Just looking for opinions. 

[Lennard]

I bought the uscartool contoured connectors for both my chargers. I like the fact that they look like a factory item, not like an add on.

[firefighter3931]

From a strength standpoint the fully boxed tubing is going to be much stronger than the contoured to the floorpan sheet metal frame connector. I used the MP bolt-in frame connectors on mine but welded them in. I also boxed in the lower control arms and had an 8pt rollbar installed. All of these things made a huge difference.  

The MP connectors cannot be seen on the car unless it's up in the air on a hoist....if that's a concern ?

For a street car I like the MP connectors, boxed lower control arms and if you wanted additional strength a set of front & rear torque boxes could be added. If I hadn't installed the rollbar a set of torqueboxes would have been added to the mix to increase structural integrity.  


Ron


Ps. Here are a few pics of the subframe connector welds, front & back as well as a pic of the boxed in lower control arm  

[cbrestorations]

the floor pan contoured ones are going to be a better chassis stiffner. those square tube connectors dont have the vertical wall height to keep from flexing. for example take a 1x1 square stock and fix it at one end horizontally and it will bow much more than a 1x2.

[Dreamcar]

Thanks for the answers so far. 

I'll mention that my plan was to also install torque boxes and inner-fender braces since they are not obvious unless you look for them. Since the car is torn down, I can do all this now without much fuss. I'm not convinced on installing the radiator support brace since its probably overkill for my needs.

I'm not building a drag or autocross car. Just a nice cruiser with likely less than 500hp but that handles well for an almost 50 year old car weighing almost 2 tones.

[cbrestorations]

drop an ls3 with a t56 in it, tubular front suspension, coil overs, 4 link rear and aluminum center diff case. that will get her down to 3,000lbs but will cost about 20k lol

[firefighter3931]

the floor pan contoured ones are going to be a better chassis stiffner.

That would be incorrect  

The boxed .125 wall 2x3 square tubing is significantly stronger than a 3 sided sheetmetal frame connector welded to the floorpan. Any competent chassis builder will confirm this  

The contoured frame connectors are better than nothing but not in the same league as a fully boxed heavy wall tube.  

Whether the OP requires (or needs) the added rigidity of the tubular connectors is a matter of preference. Personally, if I'm going to do a modification I want to get the most out of it.  

Here's a very well done custom SFC install on a factory Hemi car  

http://www.dodgecharger.com/forum/index.php/topic,41726.0.html



Ron

[cbrestorations]

in the pic you have posted, what you have is not a 2x3, looks more like a 1x2. and what you are welding to is not .125" metal either, you are welding to a sheet metal unibody. have you see the contoured subframe connectors? not exactly a piece of sheet metal...its 12 gauge (.110"). that cheezy little 1x2 will not be as good at keeping the body from twisting, its all about how tall and how wide the box is that keeps it from twisting. 3 sided piece of sheet metal lol, did you not take into acount the the floor gets welded to it to complete the box. i have done a 2x2 .125'' thick subframe connector on a convertible cuda, didnt really help much when the car was on the lift, door gaps still opened up alot. now if it was a 2x3 standing vertically it would of done better but would of had to cut into the floor.
i may have built a few chassis...

[Dreamcar]

OK, here's a question for all of you.

If I build my own like in the link that Ron posted, what size does the OD of the tubing have to be to fit inside the rear factory frame rails without any gaps? Or is it just a matter of having the same size but "persuading" the new connectors between the frame rail walls? In the pics from the link Ron posted, the new rails (no size identified) slip into the rear frame rails.

I like the idea, but I won't want rails that are so big they go through the floor.

[cbrestorations]

in the link he post, those look like 2x3 and then stepped down to 2x2 to clear the rear floors. those would work good. .125" is plenty anything over that is overkill and heavy

[Dreamcar]

in the link he post, those look like 2x3 and then stepped down to 2x2 to clear the rear floors. those would work good. .125" is plenty anything over that is overkill and heavy

The tubing used by magnumcharger (later in the thread) looks like it's not stepped down. I sent him a pm for info as its probably more something like those I'd try building.

[billssuperbird]

What would you suggest for my 70 roadrunner 

[Mike DC]

   

big heavy SC's alone  <  smaller SC's with torque boxing & other mods


Enlarging the SC's only helps until that stops being the weakest link in the chain.

The factory elected to add torque boxing to Hemi cars & convertibles without adding SC's at all.      

[firefighter3931]

CB,

Hopefully you're not comparing the wall thickness on a subframe to a floorpan ? The MP connectors are 2x3in boxed steel and 4 sided.  

Welding to a thin guage floorpan becomes the weak link. Even if the contoured frame connectors are .110 on 3 sides....the 4th (floorpan= thin) reduces torsional strength.  

A convertible is a different animal....no roof structure to triangulate strength so it's no surprise that the door gaps remained. You should have used a 2x3 tube instead of a 2x2 and mounted it horizontally like the MP connectors....that would have been stronger.  


Go to any track and look under the cars there....guaranteed you won't see anything resembling the contoured connectors. I had this conversation with my Chassis builder (during the build process) who has 30+ years experience building rail dragsters and tube chassis door slammers. He more or less confirmed my thoughts.  




Ron

[Dreamcar]

 

big heavy SC's alone  <  smaller SC's with torque boxing & other mods


Enlarging the SC's only helps until that stops being the weakest link in the chain.

The factory elected to add torque boxing to Hemi cars & convertibles without adding SC's at all.      

I would never argue with chassis experts because I am the farthest away from being one, but this is what I was thinking. Since I'm adding torque boxes and inner fender bracing, do I really need more than something like the MPs welded in on my street car?

[billssuperbird]

What is Mopar performance part number for my car thanks

[firefighter3931]

do I really need more than something like the MPs welded in on my street car?

In a word....No !

A set of front/rear tq boxes, MP frame connectors and inner fender bracing will be way better than anything that ever came on these cars new.  

I'm not telling you not to install the contoured connectors...for sure they're an improvement over doing nothing but they are a lot of work for reduced strength.  

If I was installing SF connectors lying on my back there's no question which ones to use.  


Ron

[garner7555]

I just bought tubing and built my own.  I went with overkill - 3/16" wall thickness.  I also added torque boxes front and read, lower control arm braces, and core support brace.   
I'm sure this is overkill for a street car like mine.   

[Dreamcar]

What is Mopar performance part number for my car thanks

http://www.jegs.com/i/Mopar-Performance/312/P4286869/10002/-1

[cbrestorations]

if its a full on race car then yes i would go with square stock connectors, but then ude have to reinforce the whole chassis aswell. for a performance street car, ide go with the contoured connectors. if you need more than the contoured ones you just need to roll cage it so the car wont twist and bend at all

[Dino]

I really don't know what people are doing with cruisers to need chassis stiffening.  My car is stock with a beefier front sway bar and I can throw it around a corner with ease.  Under normal driving I would never feel added stiffening.  I'm sure the body flexes when I drive it hard but it's never been an issue.

That said, when it's time to redo my car I'll add stiffeners because it surely doesn't hurt.  If you really want to add stiffness to your car then you could always add a box beam and slide the contoured pieces right over it.   That ougghta do it!

[Dreamcar]

That said, when it's time to redo my car I'll add stiffeners because it surely doesn't hurt.  If you really want to add stiffness to your car then you could always add a box beam and slide the contoured pieces right over it.   That ougghta do it!

That's exactly it...my car is being redone and is torn down to nothing...so now is the time for me to add the chassis stiffening pieces.

[Dino]

If you want the contoured pieces then don't let that stop you becaue they're harder to install.  It really won't be that bad.  The worst is welding upside down if you don't have access to a rotisserie.  But with a new, well prepared floor and some welding blankets it's ot that horrible either.  The pieces need trimming and tweaking either way so a new floor is not going to make that much worse, if any.

I'd still try to fit a thick beam in there in case you do ever decide to race that thing.   

[Mike DC]

          
IMO 3/16"wall is pretty serious overkill.  The car's existing subframe rails are like half that much.  You will just be hauling around two sets of SCs for the benefit of one set.  

Stiffness comes almost entirely from the dimensions of a beam or tube, not the wall thickness of it.  Thicker wall just makes it bend less once the bending starts.  A 5ft long cardboard package tube is stiffer than a 5ft long piece of steel rebar as thick as your thumb.  

[Dreamcar]

So I vot some info from Magnumcharger

I'm thinking I'll try to build my own out of 2.5 square tubing, and integrating it into the existing rails like he did. Plus, it'll probably cost less given the terrible exchange rate we have in Canada right now.

But, I'm still considering all options. Thanks for all your replies fellas!!!