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Subframe Connectors and unibodies

What do you guys think is the max HP that a Charger could handle without frame strengthening? I am hoping to be at around 600 with a small centrifugal supercharger. I do understand that the Hemi's at least had some additional structural support at the front.

There are many strengthening kits and options out there, but I am not sure I need this for a street car that is just going to spin it's wheels anyway.
Also, I am 60+ and my welding skills aren't what they used to be!!! :)

Unsure, but comments are greatly appreciated!

Also, AZ car, no rust on floor pans. Frame super clean.
 
My 540HP Hemi RR coupe (no subframe ties) would visibly twist when hammered, but not enough to show any cracks; without the Hemi-specific chassis gussets, it likely would have shown cracks. Typically they develop at the cowl & quarter/jamb area, from cars I've seen.
Only ran DOT cheater slicks a couple times; on Radial T/As, yup, it would just buzz them until 3rd gear.
I ran bolt-in ties an a Nova and 2nd-gen Camaro, and although not optimal, they definitely strengthened those cars: I could feel the difference.
If you plan on slicks and really launching the car, I'd definitely add ties at a minimum.
 
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I'm at around 610 hp at the flywheel with my 69 roadrunner and a weight of 3650 with me inside. I have the subframes tied with weld in connectors and have used full on slicks on the tracks many times and it was hooking hard. There are no signs of cracks or warpage.
 
What do you guys think is the max HP that a Charger could handle without frame strengthening? I am hoping to be at around 600 with a small centrifugal supercharger. I do understand that the Hemi's at least had some additional structural support at the front.

There are many strengthening kits and options out there, but I am not sure I need this for a street car that is just going to spin it's wheels anyway.
Also, I am 60+ and my welding skills aren't what they used to be!!! :)

Unsure, but comments are greatly appreciated!

Also, AZ car, no rust on floor pans. Frame super clean.
If you NEVER put decent tires on it, you'll probably be fine. Personally, I would never even try to build or drive a 600 hp car without good tires (drag radials on the street, slicks on the track), and good tires require chassis stiffening. I plan on racing my cars, so 500hp up get subframe connectors and a rollbar/cage tied to them.
If you run nothing better than T/A radials, the car will be fine as long as it doesn't get away from you spinning tires at 60 mph on the freeway.
 
USCartool connectors here. Fifteen years and many miles. No damage discovered. Lots of hard miles. Has rigidity more like a modern car. One of the best upgrades ever.

827ECDA0-B40E-43E4-A7AA-680A84FDFDD3.png
 
What do you guys think is the max HP that a Charger could handle without frame strengthening? I am hoping to be at around 600 with a small centrifugal supercharger. I do understand that the Hemi's at least had some additional structural support at the front.

There are many strengthening kits and options out there, but I am not sure I need this for a street car that is just going to spin it's wheels anyway.
Also, I am 60+ and my welding skills aren't what they used to be!!! :)

Unsure, but comments are greatly appreciated!

Also, AZ car, no rust on floor pans. Frame super clean.
in removing some of my old floors & trunk pans I discovered that at least a third of the original welds were broken.

The car (67R/t) was originally equipped with a the 440 4spd 3:54

I dont no if this is normal but this gave cause to me to install the frame connectors having near 600 hp and 555 torqued hemi.

also installed inner fender stiffeners too..

My 2 cents worth
 
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USCartool connectors here. Fifteen years and many miles. No damage discovered. Lots of hard miles. Has rigidity more like a modern car. One of the best upgrades ever.

View attachment 1393172
Looking seriously nice, Dennis. Do all 4 wheels have to be on the ground when those get welded in?
 
I really wonder how much torsional twist sub frame connectors really do? To rails in a parallel don’t do much for twisting. I believe you really need to tie front and rear together in a X to limit twist. If I was replacing rockers in a uni body I’d add the plates they put in the convertible cars along with torque boxes. I probably won’t do any additional renforcement on my 68, but if I ever start a race type car I will most likely connect front and rear with an X.
 
USCartool connectors here. Fifteen years and many miles. No damage discovered. Lots of hard miles. Has rigidity more like a modern car. One of the best upgrades ever.

View attachment 1393172
They seem to have the most comprehensive kit. i wish it was bolt in so I could do it myself, but of course it wouldn’t be as rigid then.

So the ride improved greatly?
 
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Looking seriously nice, Dennis. Do all 4 wheels have to be on the ground when those get welded in?

I've done several without suspension installed......I get the body sitting level with doors in perfect alignment , and weld em up...... never an issue
 
My 540HP Hemi RR coupe (no subframe ties) would visibly twist when hammered, but not enough to show any cracks; without the Hemi-specific chassis gussets, it likely would have shown cracks. Typically they develop at the cowl & quarter/jamb area, from cars I've seen.
Only ran DOT cheater slicks a couple times; on Radial T/As, yup, it would just buzz them until 3rd gear.
I ran bolt-in ties an a Nova and 2nd-gen Camaro, and although not optimal, they definitely strengthened those cars: I could feel the difference.
If you plan on slicks and really launching the car, I'd definitely add ties at a minimum.
Any bolt ins that you would recommend?

I’ll never run slicks on it.
 
I took 3 x 3 .120 wall tubing and made my own.

IMG_4332.JPG

IMG_4334.JPG

Mine were welded to the torsion bar crossmember and to the rear rails.

IMG_4345.JPG

I made my own torque boxes from 14 gauge sheet metal.
Again, mine are not welded to the floor pan but I did put seam sealer at the edges to fill the gaps.

IMG_4343.JPG



The car instantly felt more solid. It soaked up bumps and dips like a newer car.
The principle is simple when you look at it this way:
With an unmodified original car, the whole chassis is a series of springs. With a stiff structure, you have a solid platform that allows the suspension to work better. Taking it further, you could say that an original chassis could be compared to a person standing on a surfboard on the water. The water allows the surfboard to move in many directions due to it's buoyancy. Stand on a surfboard on concrete and the buoyancy isn't there. A reinforced chassis is like the surfboard on concrete.
 
I took 3 x 3 .120 wall tubing and made my own.

View attachment 1393274
View attachment 1393275
Mine were welded to the torsion bar crossmember and to the rear rails.

View attachment 1393277
I made my own torque boxes from 14 gauge sheet metal.
Again, mine are not welded to the floor pan but I did put seam sealer at the edges to fill the gaps.

View attachment 1393278


The car instantly felt more solid. It soaked up bumps and dips like a newer car.
The principle is simple when you look at it this way:
With an unmodified original car, the whole chassis is a series of springs. With a stiff structure, you have a solid platform that allows the suspension to work better. Taking it further, you could say that an original chassis could be compared to a person standing on a surfboard on the water. The water allows the surfboard to move in many directions due to it's buoyancy. Stand on a surfboard on concrete and the buoyancy isn't there. A reinforced chassis is like the surfboard on concrete.
Wow, you did a great job on those!
 
He’s entitled to his opinion, but I beg to differ. Before I did the USCT connectors I noticed the doors would open differently when the front of the car was up on jack stands. Afterwards, not so much...
 
BigLime - I think the bolt-ons I used way back then were Competition Engineering, or something like that.
 
Any bolt ins that you would recommend?

I’ll never run slicks on it.
Just a dumb question, but why are you planning on so much horsepower if you don’t plan on having traction as well?
 
My Welder who put in the USCartools has since passed away. Joe Sanderson. I remember he ended up in the ER with a nasty rash after grinding of the undercoating before welding. Summer heat and improper personal protection. Cannot remember if there was weight on the wheels or not. Took a lot of the rattles out when driving on washboard streets. Looks factory to the untrained Mopar eye.
 
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