Hey guys I have a question. I am in the process of having new floors and rockers stitched in on the 67 vert and I'm thinking of ways to stiffen up the unibody and give a little extra reinforcment if needed.

Let me ask you this, do you think the convertible subframe and floor structure is sufficient when in good/restored shape or are there factory defects or overstressed areas that could use some improvment? Later on this car will be getting a 351W and T-5 so I figure it could use a little help but maybe I am overthinking on an already stable platform....????

I'm thinking about beefing it up with sections of pipe or schedule 40 angle and channel iron. Maybe find a way to tie the front and rear subframes together or brace up the floor some more.

What do you think and if you have made some mods along these lines or added any connectors either aftermarket or homemade could you post some pics? Explain????

 

I don't know how the subframe is on a convertible. I imagine its nearly the same if not the same as a coupe/fastback. I would put subframe connectors on it.

If it is going to have a more powerful engine later then I would definitely do whatever I could to stiffen up the car.

I have subframe connectors on my coupe and it definitely feels different. It also has the 1 peice export brace and a monte carlo bar.

 

See I like the idea of triangulating the engine bay like you did with the monte carlo bar and export brace.

The convertible has thicker/wider inner rockers and a couple of reinforcment pans under the front seats. I just wonder if thats plenty or if Ford put in just enough to get the job done.

 

I have seen and heard of quite a few classics that were tweaked out of whack and the unibody was twisted or sprung etc.

I personally think that Ford just put in enough reiforcement to get the job done. If a classic Mustang weather it be coupe convertible or fastback is to have a stock I6 or very tame V8 then it is probably just fine as long as eveything is in good shape. With an upgraded motor however, I think that the structural integrity is at risk with out extra reinforcement.

I am actually interested in any other structural reinforcement that I can do to my coupe besides what I have already done.

 

Even if what ford did back then got the job done these cars have been abused and neglected for over 40 years so they are not going to be as strong as they were coming from the factory anyway.

The nicest homemade subframe connectors I've seen were made from square tubing. The person cut off one side so it matched the contours of the floor and then welded it in. Looked like it came from the factory with it. I've seen other people use tubing and cut a notch in the floor for it to fit which doesn't look near as good and leaves a hump in the middle of the floor.

Another option If you want stealthy look would be to run a piece of 2x3 tubing through the inside of your rocker panels and tie it into the front frame rails through the torque boxes and tie it into the rear right under the rear seat pans. It would be a lot more work but you'd pretty much have a full perimeter frame and it would be completely hidden. I got the idea from the car I'm building now. I started out doing a similar method but I built a full frame and have sheet metal floors now. If you look inside the rocker panel below you can see the 2x3 tubing. Almost a perfect fit.



This is what I ended up with in the end. Not recommending it though.

 

When I get around to building an engine...I am planning on adding the sub-frame connectors, new export brace, Monte Carlo bar, etc. Not planning on adding some huge horsepower engine to mine but still a good idea to get her some more structural strength.

Even before I do anything with the motor though I am probably going to add the subframes when I get a chance just to make the car ride a little nicer.

So far however, I have worried about the basic running / passing / kicking so to speak and replaced the floor pans, one toe board and now the fender apron and radiator support. I thought it best to get the basics really solid before adding anything additional.

 

Did you decide if you are going to install store bought subrame connectors or fabricate your own custom ones?

 

OK I'm back, sorry bout that I was out of town.

I will be fabricating my own from square tubing, not quite as elaborate as Stangtjk's (WOW man!) but enough to beef it up a tad.

The more I think about it, the more I'm actually glad that the floors rusted out of my pony. Now I can put fresh and thicker sheetmetal in than factory and will add these subframes as well.

To let yall know why I asked, a day or so before posting this I rode in a buddies 66 convertible and noticed the doors dragging and the hinges were tight. Looked underside and cancer was indeed running rampant.

Right now the suckers in the shop being stitched back together. I figured I'd let someone else with experience in mustangs and sheetmetal do the work. Probably a good idea too since it'd take me forever to do it myself.

 

Thats the problem with unibody. If there is rust then the car can literally break in half and collapse. This is really the case with a convertible that is in bad shape underneath. I saw a convertible that had severe rust damage and the rockers were trashed too. It was actually sitting in 2 pieces. The article was in a Mustang Maganzine, but I searched Google and can't find it.