Keep hearing about frame twist with 440s

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I installed DIY frame connectors (1x3 steel rectangle 14G iirc) on my 65 Barracuda, just cut and butt welded to torsion bar crossmember and rear spring hanger subframe--on a level garage floor-- and i can jack the front wheel off the ground and the rear will come up the same height. Before it was 1-2 inches deflection. Feels and sounds a heck of a lot tighter on road too.
 
Concrete isnt ever dead level. Unless you payed big dollars or it was a gubmint contract. Thats why you go get 4 cheapo spirit levels from harbor freight, and tape them in place as follows one across rear transition pan with trunk mat out, one across the top inner lip of the radiator support, and one on each rocker panel in door jamb with the sill plates off.

Your jack stands should be on the framerails just forward of the K frame, and at the rear shackles. Jack the car up and place it eyeballed as close to level with the stands in these 4 spots. Now using aluminum or steel shim stock, slowly stack the shims between the Jack stands and the framerails until all 4 bubble levels are level. Now your chassis is level and square. At this point weld in your floor pan and subframe connector.

If you want to be sure the chassis is square when you weld it up, this is the way to do it. These cars are all flexi flyers.
 
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I tack welded 2x2 box frame to rockers, then spanned 2 more 2x2 side to side under the rocker pieces. I then shimmed the jackstands til it was level on all 4 sides. Most concrete will pitch twords a drain or to the door. Mine is cracked and uneven in a few spots. After the USCT frame ties, torque boxes and inner fender supports, if I push the car on the rack to an uneven spot on the floor it stays straight enough that the wheel of the rack will hang in the air. I would say it’s one stiff fish
 
I watched the video of Uncle Tony talking about these cars supposed to have flex, and without built in flex they would crack. He obviously doesnt know spit about how metal fatigue happens. I laughed, shook my head, said what a joke, and turned his video off. I cant be bothered with anything Uncle Tony has to say LoL.
 
The person who did the floor just took sheet metal and banged it into shape, instead of buying an actual pan. It's solid just ugly as hell. I need to see if it's actually in there correctly to weld the connectors to.
 
Vamisk said:
The person who did the floor just took sheet metal and banged it into shape, instead of buying an actual pan. It's solid just ugly as hell. I need to see if it's actually in there correctly to weld the connectors to.
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Shucks, 2x3” box tube up through the floor would tie that in nice and for damn near nothing. If I didn’t put a new full floor pan in I would have ran them up and through the floor. The USCT fit my AMD pan with very little modification. The picture I am posting is from Mopardude318’s post about 10yrs ago. But it shows the slice and thru method.
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I used 1/8" thick 2x3 box as well. Layed it 3" wide, 2"tall. The box steel laying it flat only sticks up 1/2" through the rear seat foot pan. Extra padding on either side when you put the carpet down, and nobody will ever see it. I also made 1/8" thick transition plates to transition the load from the thicker 2x3 to the torsion bar crossmember. Drilled 3/4" equally spaced drain holes. Pic shown with green epoxy primer the subframe connector is pinned in place but not welded in yet. Gives you an idea.

I also relocated my parking brake cable to inboard of the subframe connector. This works fine on cars up to 1972 and puts the cable in line with the rear floor pan mounted fairlead. Otherwise the cable has to cross over or pass through the subframe connector. When I mocked the cable up I also mocked up my clutch linkages and exhaust headers. It all fits cleanly.

Hope this helps
Matt

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Matt, that looks like a plan. I don't want to just rip my floor out when it's solid. i'll probably have a professional welder do it since my welds look like you'd expect from someone with no experience. Thanks for the information!
 
TheGrateRonzini said:
Shucks, 2x3” box tube up through the floor would tie that in nice and for damn near nothing. If I didn’t put a new full floor pan in I would have ran them up and through the floor. The USCT fit my AMD pan with very little modification. The picture I am posting is from Mopardude318’s post about 10yrs ago. But it shows the slice and thru method. View attachment 1715502753
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I did mine that way , stuck inside the back frame , welded solid all the way , 3/4'' foil faced closed cell styrofoam board is a great filler to make the carpet lay flat, cant tell anything is under there .
 
I had a 67 Dart GT. I put in a 340, 727 and a 8.75 with 3.55 gears. I twisted the body with street tires. It’s the only car out of many that this happened too. Kim
 
moparmat2000 said:
I watched the video of Uncle Tony talking about these cars supposed to have flex, and without built in flex they would crack. He obviously doesnt know spit about how metal fatigue happens. I laughed, shook my head, said what a joke, and turned his video off. I cant be bothered with anything Uncle Tony has to say LoL.
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The "disagree" tag was about Tony in general. A lot of what he has to say is totally worthy of listening to! That said, I'm with you on this particular topic.

He seems to have deep but narrow knowledge about hotrodding. If you ask him what tires would be the best choice for ripping around curvy country roads, he'll gladly tell you that he doesn't care at all about that kind of performance. It seems like he knows exactly enough about chassis science for the one kind of driving that he's into.
 
Chassis science has come a long way in the 50+ years that I've been playing with cars. Back in the mid 60's a guy in my area ( nick named Froggy) shoe horned a 413 industrial engine & 4 speed in a 64 Valiant or Dart (don't remember which). On the crappy street tires we had back the, he twisted the body so bad that the doors popped open & would never close again. He found another A body, tied the sub frames together & shoved the motor & trans in it. Problem solved! LOL
 
Demonracer said:
Chassis science has come a long way in the 50+ years that I've been playing with cars. Back in the mid 60's a guy in my area ( nick named Froggy) shoe horned a 413 industrial engine & 4 speed in a 64 Valiant or Dart (don't remember which). On the crappy street tires we had back the, he twisted the body so bad that the doors popped open & would never close again. He found another A body, tied the sub frames together & shoved the motor & trans in it. Problem solved! LOL
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Yep!

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MRGTX said:
The "disagree" tag was about Tony in general. A lot of what he has to say is totally worthy of listening to! That said, I'm with you on this particular topic.

He seems to have deep but narrow knowledge about hotrodding. If you ask him what tires would be the best choice for ripping around curvy country roads, he'll gladly tell you that he doesn't care at all about that kind of performance. It seems like he knows exactly enough about chassis science for the one kind of driving that he's into.
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And that is why he needs to specify that, otherwise he is giving bogus knowledge to people who are not into the kind of driving he is into. Honestly though saying a chassis needs to flex or it will crack is BS. Take a piece of sheet steel and bend it back and forth in a vise and it will cold work and crack. Chassis flexing as well as stress points does the same thing over a period of time. A flexing chassis on a car with upgraded suspension and tires acts even more like a wet noodle and your mods will not work to their fullest advantage with a chassis moving around because the chassis is giving and moving instead of forcing the suspension to do the job it's supposed to do. I stand by my statement. Uncle Tony doesnt know what he's talking about with chassis, and flex. The less flex the better weather your drag racing or road course type racing. I stay away from his vids.
 
Vamisk said:
Is this a myth? Credible people like Steve Dulcich have told me frame twisting just doesn't happen with mild engines. (i have a lukewarm motorhome 440) Everyone keeps telling me a 440 will twist the K member and body due to weigh and power etc but the 440 isn't much heavier than a 360 and barely makes any more power than a 440.

I could understand drag engines but can anyone share their experience with me?
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Over time, the torque will twist the unibody. You'll see cracks in the filler around the A pillars first. At the extreme the drivers door won't close properly. That will take years, and a lot of heavy throttle use, with tires that stick well...
So basically it will happen. It won't happen fast. But it will happen.
 
Uncle Tony answered a question about frame connectors on his live stream last night (4/12/20) and he gave a new explanation that had some rational thought behind it.

He acknowledged that a stiffer car with connectors will perform better but the extra flex in a non-reinforced car makes them much easier to control/drive. He says that once you start to “lose it” in a stiff car, it’s harder to regain control.

Assuming that’s the actual difference comparing a stock chassis to a stiffened one, I guess I can see that. If we’re being honest about our reaction times, especially as many of us are well past middle age at this point, a car that flexes and soaks up a percentage of the variables that could upset the car could make some sense.

I fly model planes and on really fast/responsive models, it’s a common practice to set up an exponential curve to the control inputs which essentially allows you to more easily make small inputs and keep the plane from feeling too “twitchy.” You could fly the same plane with linear inputs if you are precise enough with your inputs but most people recognize how much harder it is to do that and that it’s just more fun to soften the controls and not have to change your pants after you land. It seems like a parallel consideration...maybe?

Anyway, I aspire to be able to take advantage of a precise, responsive setup and when I do drive actual sports cars, I feel like I’m still able to calibrate my inputs and enjoy a sporty, snappy driving/handling car without putting it into a telephone pole..:but my Dart Sport is a relatively lazy 300hp small block car on no-season 15” radials. Chassis reinforcement, stiff torsion bars, heavy springs, performance shocks, big sway bars or not, it’s not exactly a Formula 1 platform. Maybe it would be harder to drive like a hooligan if it wasn’t still a bit “compliant.”
 
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I have installed my homemade frame connectors on many of my builds. I am not a road racer, drag racer or pilot of top fuel dragster just a guy driving down country roads. I will keep on welding them in. If someone buys my car and don't want them, then cut them out!! lol
 
barbee6043 said:
I have installed my homemade frame connectors on many of my builds. I am not a road racer, drag racer or pilot of top fuel dragster just a guy driving down country roads. I will keep on welding them in. If someone buys my car and don't want them, then cut them out!! lol
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got some pictures of how you did that?
i plan on doing my duster with just 3X2 laying on the 3 inch side, but im not sure how close to the fuel lines that would run
 
diymirage said:
got some pictures of how you did that?
i plan on doing my duster with just 3X2 laying on the 3 inch side, but im not sure how close to the fuel lines that would run
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Every model will be a little different. Sometimes the parking brake line will need to be routed. 2 x 3 x 3/16 (or so thick) inch tubing welded in. I use a small piece of flat stock welded to the flat end.
 
barbee6043 said:
Every model will be a little different. Sometimes the parking brake line will need to be routed. 2 x 3 x 3/16 (or so thick) inch tubing welded in. I use a small piece of flat stock welded to the flat end.
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Sounds about how I did mine
 
MRGTX said:
Uncle Tony answered a question about frame connectors on his live stream last night (4/12/20) and he gave a new explanation that had some rational thought behind it.

He acknowledged that a stiffer car with connectors will perform better but the extra flex in a non-reinforced car makes them much easier to control/drive. He says that once you start to “lose it” in a stiff car, it’s harder to regain control.

Assuming that’s the actual difference comparing a stock chassis to a stiffened one, I guess I can see that. If we’re being honest about our reaction times, especially as many of us are well past middle age at this point, a car that flexes and soaks up a percentage of the variables that could upset the car could make some sense.

I fly model planes and on really fast/responsive models, it’s a common practice to set up an exponential curve to the control inputs which essentially allows you to more easily make small inputs and keep the plane from feeling too “twitchy.” You could fly the same plane with linear inputs if you are precise enough with your inputs but most people recognize how much harder it is to do that and that it’s just more fun to soften the controls and not have to change your pants after you land. It seems like a parallel consideration...maybe?

Anyway, I aspire to be able to take advantage of a precise, responsive setup and when I do drive actual sports cars, I feel like I’m still able to calibrate my inputs and enjoy a sporty, snappy driving/handling car without putting it into a telephone pole..:but my Dart Sport is a relatively lazy 300hp small block car on no-season 15” radials. Chassis reinforcement, stiff torsion bars, heavy springs, performance shocks, big sway bars or not, it’s not exactly a Formula 1 platform. Maybe it would be harder to drive like a hooligan if it wasn’t still a bit “compliant.”
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While Uncle Tony definitely has some knowledge on other aspects of these cars, he’s just proving further that he’s making it up as he’s going along on chassis reinforcement and handling. He’s out of his depth if he’s not talking about driving in a straight line.

Handling control is about precision and predictability. If your chassis sucks up all of your inputs and reactions with flex, you can’t be precise. If you can’t predict exactly how the chassis will react to a given input, you can’t control the car as well.

Yes, there’s a balance. If the chassis is rock hard and transmits every bit of chatter and noise to the driver then it will be more difficult to control. But here’s the thing, that’s not all chassis. A lot of that is how your suspension is set up, how your alignment is set, whether or not you’re in oversteer or understeer, etc. And the chassis isn’t even the biggest component of some of that set up.

And let’s face it, adding subframe connectors doesn’t make these cars all that stiff. I have a bunch of chassis stiffening on my car- torque boxes, subframe connectors, j-bars (forward chassis reinforcement), a tubular radiator support brace, etc. Yes, my car is much stiffer than it was from the factory. But it’s not anywhere near as stiff as a car with a full cage. Or even a high end modern performance car.

Yeah, the average driver would think an F1 car is insanely hard to control. But subframe connectors don’t make these cars anywhere near that stiff. Even the level of chassis reinforcement that my car has, which is more than a lot of these cars have, doesn’t make it overly stiff. If anything it still has more flex than would be ideal, even for a street car. Plus it’s a moving target- if you have 15” rims with crappy compound tires you don’t need as much chassis reinforcement, you’re not putting as much force to the chassis. If you’re running soft compound 275’s on all 4 corners even with a significant amount of reinforcement you’ll still get flex because you’re transmitting a lot more force.
 
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