Seam Welding (70 charger)

[nickstev440]

If i am planning on pushing around 600 ft-lb of torque, how necessary would seam welding the chassis be? Im already planning on subframe connectors and torque boxes (and possibly fender braces and a radiator support, all from US car tool). Also, if seam welding is necessary where would be the spots i need to pay attention to?

[c00nhunterjoe]

Depends on a couple of things.
1- will that power actually make it to the ground
2- what are you trying to do,ie: drag race, weekend warrior, road race.
3-what suspension is under the car?

[nickstev440]

Depends on a couple of things.
1- will that power actually make it to the ground
2- what are you trying to do,ie: drag race, weekend warrior, road race.
3-what suspension is under the car?

Well it will be my literal daily driver, but i plan on taking it to the strip as much as i have time to. I just want to know if putting that power to the ground (with drag radials for strip days) will twist the chassis if i dont seam weld and only have the US car tool parts. I am also going to rebuild the suspension, the front will eseentially just be all replaced (with poly bushings), boxed lca's, and .96 torsion bars. And thr rear will be xhd springs (if theyre still in good condition, if not then either new xhd's or split mono leafs), and caltracs.

[Mike DC]

  


Do the full US Car Tool stiffening package and call it good.   Subframe connectors, factory-style torque boxing, lower radiator boxing support, and shock tower-to-firewall bracing.

XV Motorsports (now defunct) came up with that list of mods using hi tech 4-post shaker rig testing on vintage Mopar B & E unibodies.  That's the best plan to grab the low hanging fruit.  



Horsepower alone won't twist a chassis.  It takes HP + tire grip and shock loads.  A Hemi/auto with stock tires won't stress the chassis nearly as much as a 440/4spd with grippy tires.  

Without the tire grip, all that horsepower is just spinning tires like you're driving on ice.  It never builds up enough G-force to break stuff.  

[c00nhunterjoe]

That suspension wont let the drag radials dead hook. The split monos and caltracs might. As reccomended above, the basic stiffening is sufficient but if you take 600 ft lbs to the track on stickies, they are going to kick you out for no cage. The cage will stiffen more then the bracing and be added safety.

[nickstev440]

 


Do the full US Car Tool stiffening package and call it good.   Subframe connectors, factory-style torque boxing, lower radiator boxing support, and shock tower-to-firewall bracing.

XV Motorsports (now defunct) came up with that list of mods using hi tech 4-post shaker rig testing on vintage Mopar B & E unibodies.  That's the best plan to grab the low hanging fruit.  



Horsepower alone won't twist a chassis.  It takes HP + tire grip and shock loads.  A Hemi/auto with stock tires won't stress the chassis nearly as much as a 440/4spd with grippy tires.  

Without the tire grip, all that horsepower is just spinning tires like you're driving on ice.  It never builds up enough G-force to break stuff.  

Ok, so would i not need to seam weld anything? Im already planning on welding the k member, for the torque, and simply because it isnt that strong from the factory. Would i not need to weld any suspension mounting areas? Or woud the braces be enough? Also, it will be a 5 speed.

[c00nhunterjoe]

One of my cars runs mid 10s at 130 mph, has similar power to what you have. Frame connectors and full cage only. Didnt even weld the k frame. Been trouble free since 1963, racecar from the factory.

[alfaitalia]

Slightly off topic...but I used to run a modified Mk2 Ford Escort with reasonable power. The first plan was to seem weld the shocktowers and anything near a high load point.....but since I had a bare shell at the time (and a new welder to play with!) I ended up seem welding just about every joint I could reach! To say the difference was noticeable would be an understatement. The whole car felt stiffer to the point it felt like I had fitted stiffer suspension! Transformed the car.....but felt a little too stiff for some. Not saying it would affect a Charger the same way....just my experience. That car was also just a street car...no track time. I'm not planning to fully weld my Charger.

[Mike DC]

Ok, so would i not need to seam weld anything? Im already planning on welding the k member, for the torque, and simply because it isnt that strong from the factory. Would i not need to weld any suspension mounting areas? Or woud the braces be enough? Also, it will be a 5 speed.

Slightly off topic...but I used to run a modified Mk2 Ford Escort with reasonable power. The first plan was to seem weld the shocktowers and anything near a high load point.....but since I had a bare shell at the time (and a new welder to play with!) I ended up seem welding just about every joint I could reach! To say the difference was noticeable would be an understatement. The whole car felt stiffer to the point it felt like I had fitted stiffer suspension! Transformed the car.....but felt a little too stiff for some. Not saying it would affect a Charger the same way....just my experience. That car was also just a street car...no track time. I'm not planning to fully weld my Charger.

Seam welding does help a lot when it's done well, I agree.  I'm just saying the lowest hanging fruit is by attacking the weakest links in the chain first.  The XV/USCT stiffening kit nails all that stuff with minimal PITAs.      

(But do weld up the weak spots on the K-frame.  The LCA mounting tubes are the worst.  The metal fatigues and they start cracking/tearing out of position.  Weld some heavy washers or something onto those spots.)



I see more potential for problems with seam welding.  You can burn off the rustproofing on the back side of a joint where it's impossible to reach again, you can fry up an area with a MIG welder and leave it worse off than before if your weld isn't great, etc.  The whole muscle car hobby is focused on the appearances of welding work more than strength (and I mean respected pro shops doing $100k cars, not just amateurs.)  


An old Mk2 Escort?  I would love to have one of those things.  That's the kind of cheap little RWD car we can never get in the USA.  Our little 70s/80s compact cars were all wrong-wheel-drive.  It contributed to the earlier muscle cars staying so popular-->valuable.  

                   

[HPP]

FWIW, SCCA prohibits seam welding in any of its stock classes for the advantage it provides. However, unless your car is stripped down and undergoing restoration, it is a major pain in the rear to do it effectively without setting things on fire or burning finishes.

[sccachallenger]

An old Mk2 Escort?  I would love to have one of those things.  That's the kind of cheap little RWD car we can never get in the USA.  Our little 70s/80s compact cars were all wrong-wheel-drive.  It contributed to the earlier muscle cars staying so popular-->valuable.  

                   
[/quote]

I guess I'm aging myself, seem to remember a few rwd compacts. How about these, Dodge Colt, Plymouth Arrow, Mercury Capri (imported from europe) also Bobcat and Comet,'78-Dodge Challenger/Plymouth Sapporo, Datsun B110,B210,510,610,710,810 Toyota Corolla and Celica, and probably some I've forgotten.Mazda RX2,RX3,GLC, Chevy vega and monza and relatives. Ford Pinto and Maverick.
Now seeing any of these cars on the street today is unlikely for sure.