Hello, I am new to the site and looking for some insight on a build I will be starting over the next few months. The car originally is a 1948 Chevy coupe, it has had the top chopped already however the wife is wanting a convertible. I have spoken with a few buddies who have gave me some good advice regarding some bracing that will be needed for the body. So a few questions I have; Are the sedan and convertible ch***is the same or will I need additional reinforcement? What are some good ways to re-enforce the body of the car? I know this has been done by many, If there is anyone who don't mind can someone post pictures of any reinforcement that as been to that year or close to it so I may get a betting idea of what need to be done. I appreciate all the input and advice as this will be the first custom I build and looking forward to the trial and error to come, thanks you and looking forward to hearing some advice.
Convertibles usually had a different frame. In the 50's, it usually consisted of an additional 1/4" thick plate welded to the bottom of the existing frame, plus a heavy duty X member. I restored a 56 Ford ragtop that had a lot of rot, and body fit issues.Since it was a complete redo, I took the opportunity to add bracing to the body. When replacing the rockers I welded in a 2 x 2" square tubing to the inner rocker, and floor, from firewall, to wheel well.. I added a 1 x 2 inside the door jam, as high as it would go. Another 1 x 2 going from the top of that, to the wheel well (reinforced). Another 1 x 2 across the rear seat bottom, with gussets up to the door jam tubing. May have bee some more, but those were the big ones.
Thanks for the advice, now when you say from firewall to wheel well are you talking about the rear wheel well?
Yes, exactly. The longer you make it, and more you triangulate the braces, the better! And if you think the cowl might need some beefing up, a 1 x 2 on the front door jam, with braces to the front end of the 2 x 2, and another going across the bottom of the dash, might be a good idea, as well.
Not to be a downer but here's my 2 cents. All this is based on not knowing your skill level either. So by convertible do you mean - A. Working top that goes up or down? B. Removeable padded top ala Carson style. Or C. No top at all. If this car has a good chop I would sell it and buy one that was unchopped before I cut the roof off of this one. Lots of people would love to get their hands on a chopped 47-8 coupe.(Me included.LOL) There is more to making a car look like a convertible than just the bracing and cutting the top off. Tops of doors where the gl*** channel is need to be reworked. Vent windows as well as the header above the windshield are just a few areas that will need to be adressed too. Everyone on this site can probably tell a story or two about finding an unfinished project with the top cut off to make into a convertible. What ever you decide. Post up some pics. As stated. Just my 2 cents............ Torchie.
No pun taken, as for the top I am going for a Carson style (removable top). As for the existing chop its is a bit of a unworkable condition. We wanted to sell the car but those who had interest commented on the condition of the chop and not in any good way. So at this time we decided to keep the car and go forward with the Carson style top. As for my craftsmanship I am no expert though I do have a creative side and good with some fab work. I will be posting pictures some time soon in the near future. Thanks for your input.
Torchie brings up some very good points. If you go with a removable Carson-style top, remember that it's either with you when you're out cruising, or it's not, (in the garage, hotel room, etc.). Convertibles had specific perimeter frames for vent windows and door gl***. Something you'll also need to fabricate if you plan to have roll-up windows. As Torchie mentioned, header panels and rear panels will need to be worked, along with latches or a method front and rear to bolt down/fasten your removable top. You'll want to think about reinforcing the middle of the body, not only at the A-pillar, but mostly at the B-pillar in order to maintain the rigidity of the body once you remove the top. Find interior pictures of bare convertible bodies of that year and you'll get an idea of the additional bracing involved. As for the frame, convertibles had a middle cross or X-member that p***enger cars did not. It was unique/specific to the convertibles, and also included additional body mounts. The following diagram (Fig. 2) is for a 1941 Chevrolet, (Chevrolet called them cabriolet's) but it'll give you an idea of what the convertible frames had from the factory.
Thanks for posting the diagram, my journey begins up to this point everyone's insight has been very helpful and is highly appreciated.
That Chevy will be an "A' body, identical to a friends 1946 Oldsmobile 66 convertible. The X-frame is not 'C' section profile but a beafier 'I' beam profile to deal with torsional loads from no roof. I helped a another many years ago build a convertible from a solid coupe by using all the convertible parts from a rusty donor. Lots of work and skill to do it correctly. Sedan ch***is requires lots of work. As an example here is Olds sedan ch***is (Top) and Olds convertible ch***is (Below). Note, Olds has trailing arm suspension with open driveline -v- Chevy parallel leaf springs & torque tube. Lots of sheet metal work coming up.
^^ those Oldsmobile frames share nothing at all with the Chevrolet frames of the same era. not one part. not even close.
Correct, I agree completely. The Chevy is top hat design with ladder frame X-members; Olds is totally different design being open 'C' profile with beefy centre X-member in standard format. Chevy body is smaller 'A' convertible like Pontiac Torpedo and Olds 66 & 68 with short wheelbase, not the larger and longer 'C' convertibles like Olds 98, Buick Super & Roadmaster or Cadillac 62 that share nothing in common with smaller bodies. This was just an example of what would be required to strengthen the Chevy frame sufficiently to facilitate a convertible conversion. Without modification the body ch***is combination would flex and twist and place undue stressors on all areas leading to premature failures due to torsional and beam issues.
Thanks for the clarifaction in regards to the condition of the top chop as that does make a difference in wether to cut off the top or not. For what it's worth if I was going to do this ( and I have considered it) especialy on a coupe I would not use a back seat. I would treat it like a bussiness coupe. I would build some horizontal x-style bracing to go from side to side as well as a verticle cross member behind the front seat going from side to side as well. Then I would have a snap in cover made to hide it all so when the top is off it would just look like a tonneau cover. (All though in truth I can't really remember ever seeing a car with a carson style top that had the top off. LOL) The frames on these cars are extremely beefy regardless of the model. What you don't want to happen is when you shut the door the topped off B piller pushs in or flex's so much that the door will pop open while driving. The horizontal bracing up toward the top of the body tub will help to prevent that. Good luck. Have fun. Post pics. Torchie.
Here's a real convertible and OEM body well etc for folding top. This may ***ist in fabricating suitable reinforcements panels. Note no rear parcel shelf as this is where top stacks when folded.
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