Drag Racing Tech - Floor pan strength.




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98 grmrpr
04-23-2012, 05:01 PM
Hey guys was looking at my floor pan, where the cut out for the torque arm is. Just curious as to weather there is any strength in this area, and if I could cut the floor out basically from the rear seat wells to the boot floor so it would just be a flat floor. I was thinking of laying in a 1 inch square tube as like an upside down u to follow the floor at the start of the cutout, boxing the rails were needed leaving in the factory brace and triming the tunnel out like my rear to make it removable. This would be a good topic for you JL as your floor is all cut up. Any thoughts, thanks guys.


Doug G
04-23-2012, 05:10 PM
The floor in a uni-body car is a big support area...I wouldn't do it.

Now if you were to make a frame connecting the front and rear (triangulated).... then you'd be OK.

98 grmrpr
04-24-2012, 12:36 AM
Hard to explain but that is kind of what I was thinking. Have you or anyone else got anymore specifics on this. A rough diogram, unfortunatly I dont know how to upload drawings.
Thanks guys.


JL ws-6
04-24-2012, 04:03 PM
98 with all the tubing that's going thru my car now the floor is no longer the strength part of the car. We will be patching it all back up and closing it up to support the floor where it was cut fwiw.

I understand what you're saying you want to cut out where the rear seat buckets sat and make that a flat area. I have seen this done, but not on anything with a less then 25.x cage in it. I would not do it, if you haven't already, unless you have alot of extra bracing in that area. I could, with what we did to my car probably get away with it, control arms are actually attached to the chassis, granted they're in line with the stock mounting points, and a bolt will go thru both the stock mounting point and where the control arm itself is.. but they're on the cage work. The rear shocks, also mounted to a bar that's tied to the cage, right thru the rear deck area.. shocks are also now no longer on the factory body/frame... pretty much everything is all built to the actual cage now. So, the floor in the back is just there for the ride.

What you're doing (if I can picture it), is clearancing the rear tunnel where the tq arm and center section are, so that there's easy room to work on it under the car. if this is what you're doing, you can do this, but I would make sure that you use mat'l that's not paper thin that will still have a little strength in it. I'd bead roll an X in the panels as well just to add some more rigidity to it, just for the sake of doing so. If you're making that removable so you can get the center section out thru the top (have seen this done), I would build a small frame around the area out of some type of tubing or square stock to give the area some rigidity back, and give you a way to easily mount the dzus tabs to it. I thought about doing that but with the 12 bolt staying in the car I didn't bother, not really worth it, being that I don't have anything to get to there that I could do from the top.

I have also seen, a car that wasn't a full chassis setup, street deal with an 8 pt that the rear buckets were cut out of just to put a flat plate in for muffler space, fwiw. But, the tunnel was untouched on this car.

Doug G
04-24-2012, 04:52 PM
This is a full framed car, but you'll get the idea....Guy I knows shop http://dcperformance.net/

http://benchseatracin.smugmug.com/Cars/DC-PERFORMANCE/Lous-68-Chevelle-Project/i-jHbtT5B/0/L/Lous-68-Chevelle-4-18-12-6-L.jpg

98 grmrpr
04-24-2012, 05:56 PM
Hey guys, thanks for taking the time for your thought out responses! Im hearing you all and thought I might be able to add a bit more input about the car.
I have through floor frame connecters, have ordered Burkharts new short torque arm relocation kit with my diff. I was thinking of doing a tube type brace from the frame rails straight across kicked up like Dougs brace (like a tailshaft loop following the tunnel). So looking underneith it seems like the area was dead metal.
This is were I was thinking of doing the cutout, I drilled a series of 6 mm holes so I could paint a outline. The hole follow the frame rail.
It just seemed that with the repairs needed to fix the current sheet metal, it would be a better idea to replace it, I really couldnt see that there is much to upset. Like you said JL the shockers mount up top, my new coilovers will run out of this stock position. Going up to the top factory brace I would have thought that the strength would still be retained for the shockers.
I havent yet made anymore cuts, let me know what you guys think.
http://i817.photobucket.com/albums/zz98/sbc98comaro/100_1614.jpg

JL ws-6
04-24-2012, 06:11 PM
If you had ran a bar between the main hoop, that contoured the floor board, and could run a couple bars off it up to the back portion of the cage I would feel alot better about that.. then you would have the back of the car tied up alot better. I would be a little leary about cutting that much out.

Boxing back in what you already have cut out, I don't see a problem with, that's a common mod. Doing what you're thinking about I would not do unless you had a 25.x



That's me, you can do what you want your car, but that's alot to cut out, and you are going to lose strength between the frame rails in that area.. and if you have the shocks attaching like they do from the factory, and you now have coil overs on the car (putting a stress in a different place due to location of the spring) I would be a little concerned about it.

Again, do what you think is right there's tons of these cars around that have been done different ways... I don't think by doing that the car is going to fold in on itself. That's just a really big area to do that to, and it's probably not really nessassary.

What metal repair are you talking about that you don't want to deal with, rust underneath? From that picture and the pictures I have seen in your other thread everything looks pretty sound on your car... unless there's something that isn't visable you're concerned with?

98 grmrpr
04-24-2012, 06:32 PM
Thanks again JL, coil over's will run in the stock shock location, with no other springs, just one unit. Your right the body is solid no rust really needing attention, I was just looking at the small repairs to the fuel pump wiring, the seat belt holes in the wells. Being honest all very easy repairs just thought it may be worth while just to lay some new sheet in there if the metal was useless any way.
Seem's it is needed and I will give it a miss, box in what I have already done, fix the small repairs and be done with it. Thanks for the heads up guys, need all the help I can get being in Australia!

JL ws-6
04-24-2012, 06:42 PM
Probably the better idea. Alot less work in the long run, which wouldn't have really give you any return.