Technical 49-54 chevy 4-link: Why is everyone cutting the floors?

Exactly, and even if it does not get that bad over the time you own the car, it can make for an unacceptably unpleasant ride, in a vehicle that could otherwise be set up fine.

 

Near as I can tell, likely differences are tension vs. compression, possibly in torsion too.

This is why you measure carefully and try to mimic the original factory setup!

 

I've got a '47 Aerosedan, and while not the same, I think the situation is similar with triangulated 4 links and lowered cars. I've been under mine a lot recently formulating a plan.

You've now seen/been told why the upper link protrudes into the floor on super low cars. One reason you see trunks all cut to heck with those "big giant notches" protruding up is that there is no clearance between where you need to run the rear cross member for the upper bag/coilover mount and the top of the rear end pumpkin, even on a mildly lowered car. If you bend/jog in it to clear the pumpkin, you will still have to cut the floor to clear the jog (at least on my car). The same problem exists on a 2 link/trailing arm setup.

I'm not planning on running bags and I don't want to cut floors, so I've pretty much given up on the four link idea and will probably just run a good pair of lowering leaf springs.

Spend some time under your car pondering the "how" of the various setups you've seen and the "why" will probably become clear.

 

Do truck arms allow the rear to be lowered enough without them coming in contact with the floor etc.? This is assuming a c notch has been done? They really appeal to me for simplicity's sake. Jus seems that exhaust routing would be a pain.

 

Would depend on where/how you mount the arms, also lowering blocks are a possibility , run the exhaust torward center by the pivot at the tail shaft trans and back out to sides to keep out of the way of arm movement

 

If you use 2" blocks you should be able to get them under the floor.

As has been mentioned, the exhaust will be tricky, but not impossible.

One thing that I have wanted to try, but never had the chance, is a "bent link" for the upper links or a triangulated 4-link.

If they were made sturdy enough, they should be able to clear the floor. As long as point A, and point B are where they need to be, the shape of the link does not matter.

Of course, that would probably screw with the exhaust, too.

 

Well gimpys, I'm with you. A few decades ago I went to Chris Alston to have a 57 Chevy halved , and got a book from him on instant center among other things, then a few years later A chassis builder for drag racing Don Long tried to explain polar moment of inertia. My lesson from both is that if a true working chassis is to be designed it can't be explained by a few pages

 

There is a lot going on, to say the least.

Most folks think suspension is pretty simple. It ain't.

An SAE-ass-ton of engineering went into even a Model T. Things just got exponentially more complex from there.

 

Easy way to deal with the upper links is to keep the torque tube so you don't need them Hosted on Fotki Though it still was a bitch fishing the exhaust through to the back.

 

I just finished going through all of this topic that past 2 years building mine and I couldn't find enough room to get the car to lay frame and not modify the floor. Regardless of pinion angle the drive shaft input on the axle comes well above the back seat floor. In fact before the car was bagged, saggy leaf springs and 3" blocks would make the pumpkin hit the floor no problem. Knowing that I wanted to keep my back seat modifications to a minimum, I tried to come up with a way to prevent the need for cutting holes for the upper arms. I looked at bent arms but there isn't enough room between the back seat edge and the axle while keeping good suspension geometry. I might be possible by doing a revers triangulated 4 link like a lot of the mini trucks but I didn't want to did into it that bad. I was already putting a whole new suspension in the car, I might as well cut a few more holes.

 

That's pretty much how they all end up looking.

If you want it down, you have to cut.

 

I’ve used truck arms on a couple 54’s and a 36 Plymouth. About to do another 54. They work great. Tim

 

Old thread, for sure, but since it came up, CPP is making proper copies of the GM designed truck arms.

If you cannot dig them out of a yard, you can get brand new ones:
https://www.summitracing.com/parts/clp-6072sta-k

 

I know its an old thread but have you used those arms with a bag set up? Thanks