Hey guys, I'm looking to turn a 1940 Mercury coupe into a carson top custom. My question is, does a coupe's frame need any modifications like boxing or extra bracing to account for the soon to be cut off roof? Can I permanently brace the body somehow to keep the doors from moving? What are the factory differences between convertible and coupe frames?. I'm looking for first hand experiences, has anybody done this? Pictures please. Thanks
I just picked up a 41 olds and I can tell you once the roof is off the quarters flop in and out like tin. I was also thinking about a Carson top. I asked a guy today that does roll bars about putting a u shape bar around the top of the panels and then turn down to the floor. To weld the quarters to so that they stay in place. Something like this. Sorry for the bad pic.
Most convertibles have an "X" member in the frame, not sure what Ford did since they already have a nice "X" member in the frame, but just about every true convertible that I've seen has a lot of body bracing added to them.
Ok, here is a 40 Merc frame that I have (from a coupe as well) From what I've read is, that there are some extra bolt on plates and braces on a convertible frame that the coupe frame doesn't have. Please confirm, does anybody have pics?
I worked at the Frame Plant in the Rouge complex for a few years in the 60's. The convertible frames were of a heavier gauge steel. There was a stretch of wall with all types of frames from the Model A through the (then) present.
Ford convertibles and woodies of that era used a frame that was 1 gauge thicker steel than the coupes and sedans. There is also an additional brace in the A pillar area of the frame. I would imagine they did the same on the Mercs.
What happens with the frame depends on if its a show car or a driver. If you intend to drive one then yes the frame needs to be beefed as well as the body where the B pillar would attach. Probably wouldn't hurt to beef the cowl and package shelf area as well.
I don't think the frame is an issue. I agree with turbo Joe, that the body would need to be braced. The upper part of the quarter panel is awful weak without a top. You might have an issue with the doors closing properly and even staying closed as you drive the car.
Mr. Miller, I don't know where you got your information from but it's simply not true. The Ford Chassis Manual for 1941 passenger vehicles lists two frames. One frame, 11A-5005-A for '41 and 21-A, 51-A, 1942 thru 1948 is for "closed models". 11A-5005-B, also for later years 21-A and 51-A, was used for the model 76 Convertible Coupe and the later model 71 Sportsman. The difference between closed cars and open cars was different attachment point holes and welding on the Convertible models to attach the "X" member. All were the same gauge.
Miller's info shows up through 1940. He is correct. He didn't say anything about post-1941, and the Merc in question is a 1940 anyway.
My '40 Chevy convert has another "c" section on the bottom of the frame from other models and both the "A" and "B" pillars have more gussets where the jambs and floor attach. I would at least want to beef up those areas to minimize cowl and quarter shake. I would err to the side of stout in the bracing Common sense rules and try to keep too ugly out of the improvements.
I have been building and restoring early Fords since '62 and can say I never heard of thicker frames for Wagons and Convertibles. Commercial vehicles, yes. I can quote from Loren Sorenson's book "Famous Ford Woodies". On the '40 Ford Woodie, "On the assembly line the wagon body was dropped on a V-8 passenger car chassis". Lorin was an authority on early Ford from Model A and up. So that tells me that '40 Wagons and passenger cars used the same chassis.
I have 40 convertible project. This is a brace that one rod shop installed in a 1939 Ford that I saved as a reference in case the body is too floppy. I tried to go back to its original links but the car is gone. I made a PDF of the pages that shows one nice brace arrangement that goes side to side behind the seats. The 39 and 40 are different cars but the brace may be adaptable to the 40 with a couple more legs behind the seat or attached to the vertical braces between the trunk and seats.
Thanks for all the replies, I'm still looking for pics of a 39-40 Mercury convertible frame. I get that I can box the frame and reinforce the body it with extra braces, but I'd still like to see what the factory did.
Although my body still has a roof and due to some OT suspension modifications, I fabricated and added these vertical rear brackets that tie the rear X-member legs to the frame rails top and bottom, replicating OEM brackets at the front of frame under cowl. Torsional twist will be reduced with strength increased. I also added horizontal triangular shaped plates that are bolted to frame rails, top and bottom where the legs attach each side, further enhancing strength and minimising torsional twist as everything is tied together. Simple and strong. I've a friend with a convertible and his frame X-member is OEM deep cross section I-beam. I've also seen other manufacturers reinforce OEM frames with 3/16" flat steel strips welded to frame and X-member legs for reinforcing purposes. Sent from my SM-T355Y using The H.A.M.B. mobile app
Hi... I have a 41 Caddy convert and the frame X member which is 3/16" hadn't been reinforced.across the X.....later 41 Cad's had the X member reinforced top and bottom to stop twist...I have found the factory updates and where they stiffened the chassis... I think the body was twisting and doors would fly open..Have a family member bring a 41 Caddy convert to Australia just recently and it was the same as mine without reinforcement....I have since found out about the modification at the factory and have made the top and bottom 1/4" plate X member and installed and has definitely stopped the door gap from spreading when jacked up under center of of the chassis ...the factory also recommended to box the chassis wheel arch rise to be boxed as well....
This is what I did to a friend's 42 Chevy PU when I installed a 46 Olds crossmember similar to above however using OEM trailing arm setup. I used flat plates that I referred to earlier to tie X-member to frame rails, top and bottom at both ends of car. I still had to do a bit more work to do however you get the idea. It reinforces the frame rails and ties everything together reducing that inherent torsional twist. I did similar to my 35 Chebby tub and the doors don't pop open when driving! I used a large flat plate in a similar fashion, extending from centre area and forward along the X-member legs attaching to the top and contoured to clear the transmission shape. The frame doesn't flex now and is rock solid. Simple but effective with HT UNF button head bolts, washers and crimp [lock] nuts.
Not a '40; but I added inner framework of 1" square tube to my '47 similar to sketch in post 2. I also added an "X" to the divider between the cab and trunk. This really stiffened the rear body once the roof was cut off. Maybe ask Kube on the FordBarn about the factory frame reinforcements.
Not a '40 Merc, but a friend of mine has a '47 Ford convert, the door jambs are reinforced by substantial iron castings that extend up the jamb, and across the interior in front of the rear seat riser. Don't know for sure, but I'll bet they bolt to a frame crossmember under the floor like the one shown in J. A. Miller's drawing. Something similar could be easily fabbed.
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