Body twist

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I agree with most of what has been posted.

Unless the car is already off the frame, don't worry about boxing the frame. Plus there is alot to that to do it "right".

If, and that's a big if, you start hooking all that torque you will end up in rollbar territory anyway which negates the need for frame boxing.

Look at the Cutlass below, that's just shy of 600# of torque with a stock frame.

As far as the body braces not helping the frame, and visa versa, that's false.The 2 together are much stronger then as seperate pieces.

Ever do any house framing? What happens when you add 1 piece of plywood.Bam stiff has hell. Not exactly the same but you get the idea.

This is were poly or even solid bushings really help.

Also for a torque monster go with a mild gear (3.23) and a tall tire.

This is where the B.O.P. motors shine when compared to the typical small block.

Have fun with it.
 
Yes, the body shell acts like an A frame on top of a flat section. It adds a lot of torsional rigidity that would otherwise be impossible to get with a mere flat section of ummm.... stuff welded together (ran out of words).
 
As far as the body braces not helping the frame, and visa versa, that's false.The 2 together are much stronger then as seperate pieces.

You can brace the body as much as you want but that would have no effect of stiffening up the frame unless you have a unibody. When we using a G body for a circle track car we had a full cage with a front hoop. The right front clip would move almost 1/2 inch upwards while cornering even though the frame was rewelded, boxed and x'd and the front clips were braced by the cage in the car and the front hoop was attached to the front clip by 3 posts on either side and we used solid body mounts. Please tell me how body braces would stiffened up the frame when the body is suspended from the frame with 12 bolts and bushings....
 
pontiacgp said:
As far as the body braces not helping the frame, and visa versa, that's false.The 2 together are much stronger then as seperate pieces.

You can brace the body as much as you want but that would have no effect of stiffening up the frame unless you have a unibody. When we using a G body for a circle track car we had a full cage with a front hoop. The right front clip would move almost 1/2 inch upwards while cornering even though the frame was rewelded, boxed and x'd and the front clips were braced by the cage in the car and the front hoop was attached to the front clip by 3 posts on either side and we used solid body mounts. Please tell me how body braces would stiffened up the frame when the body is suspended from the frame with 12 bolts and bushings....

In theory,you are correct.

In real life on the street,ANY body bracing you can do helps,esp if you have t tops.If you take the core support to fender braces off my t top GN,you get cowl shake...

These cars are pretty flimsy even for full frame cars.Ever seen one launch at the strip carrying 1 front wheel?
 
Yes, they are body on frame, but the body CAN strengthen the frame if it is mounted rigidly enough to it. GM's engineers designed these cars in such a way that much of the NVH (Noise, Vibration, Harshness) was isolated in the chassis when the cars were new. This is why the OEM body bushings were full of holes, to cushion the ride. All that was fine on a sub 200 hp car that only had to be smooth. The frame flexed and twisted a bit, but it did not affect occupant comfort. However, since NVH is not our primary concern anymore, we can change that and make the whole composite structure much less flexible. The biggest single thing you can do is rigid bushings made of polyurethane or aluminum. These will tie the two structures together and make a much more rigid whole. At this point, the body's torsional rigidity matters a great deal. The stiffer it is, the less the frame will be allowed to flex, just like in a unibody vehicle. After all, with more or less solid mounts it becomes in effect a unibody vehicle. In this case, that is a very good thing.
 
85 and broke....I think you'll agree the strength of the frame is far greater than the sheet metal of the body. In order to brace the body to stiffen the frame you'd basically have to mount the body directly to the frame and add so much bracing, since the body is only as stiff as it's weakest points the added weight, the car would weigh a ton.
 
how mch of a PITA is installing poly body mounts?
 
2000.malibu.ls said:
how mch of a PITA is installing poly body mounts?

it's not a hard job if the body mount bolts don't break when trying to remove them....remove them from one side and lift that side of the body off the frame enough to remove the old bushing and install the new one.
 
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