Valiant63
Early A-body Valiants
That’s what I would do, too.
I would also keep the structure and support of the old crossmember but just add a piece above it to attach to the floor.
67-76 floor into a 65...
- Thread starter Cuda416
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That’s what I would do, too.
I would also keep the structure and support of the old crossmember but just add a piece above it to attach to the floor.
I believe the crossmember is complete side to side and the center supports the floor. So aligning the floor cut and adding a extra support for the different year flooring should work
Cuda416
Well-Known Member
What Stephen is talking about is that fact that the floor completes the cross member as a boxed structure in the same way the frame rails and some frame connectors use the floor.
Think of it as a "torsion box" not to be confused with torsion bar. Torsion box designs create an extremely rigid structure much like how honeycomb composite panels are made and for the same reason. Light weight, easy to make and cheap. A cardboard box is much more rigid when the top is actually taped shut.
The problem I am trying to avoid by replacing (possibly) the centered hump, is limited transmission choice. Right now, the only thing that will fit (I think) is the 904 or a manual. No way in hell will an overdrive of any type fit. Since I'm replacing the floor, my thought process is, at this time, to "fix" the problem as I see it to "future proof" it for other options.
At the end of the day, I need to account for the narrower frame rail placement which affects how the transmission cross member is attached. If I cut equal amounts from the center point, I need to get even more creative with a cross member. It might simply not be worth is and the simple solution might be to simply add material from the existing hump, up to the floor and be done with it.
That's just one of many options I'm looking at. Another is to cut the hump out of a newer A body and graft that in, but I still have the width issue and trans cross member to deal with.
Thanks
JDMopar
Well-Known Member
I still like your examples in posts 19 & 20.....especially 20! Maybe you could beg, borrow or steal an A500 long enough just to use for fitment purposes. That way, you won't have to make modifications later on if you decide to use an OD trans. Looking forward to more pics of the progress when you get around to it.
Cuda416
Well-Known Member
I still like your examples in posts 19 & 20.....especially 20! Maybe you could beg, borrow or steal an A500 long enough just to use for fitment purposes. That way, you won't have to make modifications later on if you decide to use an OD trans. Looking forward to more pics of the progress when you get around to it.
I have to admit, I DO like those options better. I might have a 727 of my own soon so I could use that to start.
JDMopar
Well-Known Member
Yep, and a 727 would help you get the firewall/floor pan pinch weld to where it wouldn't be a problem like a stock early A. I suspect that whole seam may need a little adjustment. I believe that I would try to make the firewall fit the new floor pan.
Cuda416
Well-Known Member
Yessir, that's the plan for sure.
Garethw
Mopar. Because rocket science is too easy.
I’m stuffing an A500 in my 65 Valiant right now. I boxed in the torsion bar cross member before I cut the hump out just for good measure. Also had to cut a lot of the tunnel out. My floors were trash anyway so what’s a little more cutting. New tunnel will definitely be larger.
Cuda416
Well-Known Member
I knew we weren't blazing any trails. I'm glad this is a topic that has some interest. We won't be the only people benefiting from this. What are you planning on doing to replace the hump? My concerns is that it's a major stress point due to the torsion bars. Frame connectors will help but I think there still needs to be something to tie the two sides together.
Garethw
Mopar. Because rocket science is too easy.
@Cuda416
I’m going to weld in a hoop from 2.5” bar stock, 3/16” inch thick. Then I’m going to make the trans mount member beefy enough to carry load. I may triangulate the torsion bar member to the outside frame rail, but that may be overkill. This car is only getting a very slightly warmed up 318.
I’m going to weld in a hoop from 2.5” bar stock, 3/16” inch thick. Then I’m going to make the trans mount member beefy enough to carry load. I may triangulate the torsion bar member to the outside frame rail, but that may be overkill. This car is only getting a very slightly warmed up 318.
Just be mindful of how much weight you're adding vs strength. The strength of the torsion bar crossmember comes from the "depth" of the member itself, not from the thickness of the top or bottom plate. You can easily add a bunch of weight without making an appreciable increase in strength...
Cuda416
Well-Known Member
Sounds good, please post your work here so there folks (namely me, lol) can see what other folks are doin'
Garethw
Mopar. Because rocket science is too easy.
Definitely understand that. A shear web is always better. I also did the boxing because it’s a convertible and I was gutting the entire floor and tunnel and didn’t want to risk any twisting.
@Cuda416 I will definitely post pics of how I go about this. I’ve read all the threads here of A500 installs but I’m sure mine will still be different.
@Cuda416 I will definitely post pics of how I go about this. I’ve read all the threads here of A500 installs but I’m sure mine will still be different.
Cuda416
Well-Known Member
100% agreed on this. That was the reasoning behind my "layered" approach. i don't think my little two layer idea will come close to the height of the original, but since it's layered, I'm hoping for an effect similar to how layered composites work. I have some other variations of the idea floating around in my head but nothing solid yet. I think first and foremost, I need frame connectors, which will allow for some nice "boxing" and "triangulation" options. Of course, instead of 1/4" bar stock as a second layer, I could cut a profile, say from the 1/4 plate, but keep it's height down to an inch or so, less so at the top and more along the lower sides, much like the factory shape. A box like that "should" be stronger than the 11 gauge sheet metal used if done properly and still be as strong and light as the original. (maybe)
Garethw
Mopar. Because rocket science is too easy.
Here’s a pic before I cut all of the tunnel out. It does show better how much of the original hump had to come out. You end up losing one of the left side bolt holes for the trans cross member. I’m going to add another when I design my new one, no biggie. You can keep both bolt holes on the right side, barely.
Garethw
Mopar. Because rocket science is too easy.
Here’s my hoop partially welded in. Also a pic with the original hump on top for comparison.
Cuda416
Well-Known Member
Looks good, thanks.
As I look at this, it appears the cross member hump lines up with the OD unit, is that correct? The pass side cut looks like it it butts up to the tran cross member support bolt hole and the drivers side, about 3/8 of an inch passed the first hole? If that's right, then I can do the same and be pretty sure any future transmission swap that includes an A5xx should fit as long as the rest fits a 727, yeah?
How high is it compared to the original?
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JDMopar
Well-Known Member
Keep in mind, that some of those ribs on the sides of the OD unit can be trimmed down or cut off. That alone may mean being able to use an OD transmission within the confines of a stock later floor pan like the one you are adapting to your early A. It is possible to put an A518 into an E body without cutting the floor pan or crossmember, by cutting and trimming the ribs. I know that's an apples to oranges comparison, but with the crossmember mods you're doing....it may gain you enough room to get one in there and not have to bulge out the floor pan to where it's a pain in the *** to get carpet to fit. If you can get a 727 to fit, chances are you can get at least an A500 in there. An A518 is longer than an A500.
Garethw
Mopar. Because rocket science is too easy.
@Cuda416 Yes, the hump does go around the OD unit. On the passenger side, you could probably leave a good 1/4" past the inside bolt hole. I took a little more off than I probably had too. On the driver side, I would say take the inside bolt hole along with another 1/2". I had to take a little more off after initially cutting out the original hump. I'll get you some measurements when I'm at home tonight, including the height. My goal was to keep at least 3/4" clearance between the trans and the hoop/floor. There was no way around cutting out the old tunnel to make this thing fit, totally worth the OD though in my opinion.
Cuda416
Well-Known Member
JDMopar
Well-Known Member
Just performing CPR on this interesting thread. As hot as its been here, I imagine it might be too hot in S. TX to want to slave over a hot floor pan! 
Cuda416
Well-Known Member
So I guess its time for an update.
We ended up cutting it right over the torsion bar crossmember as suggested. The rear portion dropped right in. Fits like a glove. The front portion needed to be trimmed along the side a bit. We trimmed starting 1/4 inch from the sides, then back to where the floor levels off. This cut was a wedge so it started at the front and thinned out as it went back.
Problem now is of course the firewall. I'm going to either get a cut out from a junk yard car or make a tunnel extension to cover span the gap from the new tunnel to the firewall.
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