I'm wondering which is considered to be the better chassis, the 56 Buick with its coilover rear or the Olds with the leaf springs. Also, between the 2, which has the better engine and transmission? Looking for feedback of comparisons between the 2 for the 54-56 model years.
@scotts52 Although I am generally a Buick fan, it is in spite of, not because of, the torque tube driveline and the Dynaflow. I also very much like Oldsmobiles, especially ‘49 up. As for the chassis, the front end suspension is essentially the same. The big difference, as you have mentioned, is the coil rear suspension. For a ‘stocker’ it doesn’t matter much, but for ease of modifications, I think the Olds leaf spring has the edge. The contours of the Buick frame in the rear do not easily sccept a leaf conversion. Ray
Tell me more. From looking at pictures online, it looks to me like the frame is basically the same. It looks like you could remove the crewmember that is for the coilover setup and weld in one from an olds and then adapt the leaf springs. Of course looking at pictures is nothing like having them side by side.
I had a 56 Buick, and I wanted to put in a 700r4, but they had a closed driveline until 1960. Converting to an open driveline is quite an undertaking, so I would go with Oldsmobile because it already has an open driveline, which makes trans swaps a ton easier.
Bestway to modify the Buick suspension is with a 4 link and panhard bar. Still not super easy. See my build thread onmy 49 to see what is involved.
Assuming an engine swap is part of the conversion, I don’t think the trans conversion is especially difficult....it is the rear end that poses more of a challenge (see posts above). I agree with you, the Olds is easiest overall. Ray
Here is where I'm at. I'm piecing together a 56 Oldsmobile 98 convertible. The frames are impossible to find and I really don't want to spend $13K + for a custom frame. I can find a Buick frame easier. I have the Olds convertible cowl, doors and a 2 dr hardtop for parts. I have a 56 Buick Century Olds tub and what once was a convertible. It's sitting on some kind of homemade contraption that someone evidently thought would pass as a frame. Do I throw the Buick body on a Buick chassis and do all the cut and paste to transform it into the Olds but on a Buick chassis, or can I modify a Buick convertible chassis to be like the Olds? This isn't an effort in practicality. It might be better to go buy a more complete project but that is not me. I love a good challenge. This is a labor of love and skill to save what is basically just a bunch of parts and transform it into something beautiful. I don't want a custom frame. Don't want to spend that money on a frame and I also like original equipment. So I guess my point in a nutshell is can I build a 56 Oldsmobile convertible on a Buick platform? Can I turn the Buick platform into an Olds? And for those who don't know, the frame is convertible specific. Thicker gage metal and convert specific x member. Not sure how well I explained all that. Made sense to me
I see you haven't had any luck finding a frame yet. They will be out there. I spent several years looking for a left rear 1/4 for my 98 convert before I found a car being parted in Alaska. The seller pulled it apart for me, boxed it up and shipped it to New Zealand. Not a cheap exercise but they are still out there. Good luck. Russell.
Having just sold my 48 Buick convertible, I will say that the original,convertible chassis is not very stiff. In fact, you can visibly see the cowl shake when you drive on a rough road. I'm sure the Olds is no different. Just factor that into your decision. Dont even think about using a sedan chassis unless you reinforce it. I know someone who has a complete, disassembled 56 Olds, if you're interested. Its in NC, however.
You can do anything if you have enough time, money and talent but should you? If it was me, I would be searching junkyards for an Olds 98 parts car, a picked over 4 door sedan from a dry climate shouldn't cost more than a few hundred bucks. Find out the difference between a sedan and convertible frame, usually they are practically the same except the convertible is reinforced here and there.
An alternative would be the chassis out of an eighties or nineties full size GM rear drive sedan, Olds Chev Caprice or Buick and use the chassis, floor pan, drive train, suspension etc. You could even keep the air conditioning if you are careful.
@Rckt98 Nope, nothing yet. Maybe you can answer me this though. What are your thoughts on building this on a standard hardtop chassis, that is, the body, and then while I'm doing that I can keep looking for the correct frame? Do you feel the hdtp chassis would work for layout and planning at least? I wouldn't go down the road on it. I just need reference points to build from since everything is in pieces.
The Buick will ride nicer, but the Olds has a better engine, trans and an open driveline. I love Nailhead engines, they dress up great, but you can't beat a Rocket engine with a hydromatic.
I am sure the only difference between the frames is the steel thickness on the X member. I still have my convert frame and body at home, but will probably be putting the project up for sale soon, as I will never get it finished. If you need me to check anything on it for you, only too happy to help.
The Pontiac frame (long WB) is very similar to the Olds. Interchange is doubtful but I bet there are enough similarities. Front suspension is very close & rear springs just different enough that they won't interchange. The old Blackhawk/Hein Werner data goes back to the mid 50's.
@Rckt98 So you think this will work on a hardtop frame? https://www.classicmuscle.com/convertible-frame-x-member
You can use a hardtop chassis just do the research on the difference as far as strength and build your own crossmembers and X pieces that make it a convertible frame. You are building a one off car so building your frame stiffeners shouldn't be a problem. If you are worried about doing that go find a box top Caprice and use the front and rear sections of the frame and make your own middle pieces. that would give you modern brakes and steering.
I guess this is for a chev? You would have to get the dimensions I guess and see if it will work. Olds chassis may be wider but I don't know. How about adding plates to a hardtop chassis x member to strengthen it? You aren't going for a 100% restoration.
A hardtop frame should have the X member in it but the convertible frame has the X member beefed up. (Sorry, I can't remember the specifics.) Honestly, I think boxing the frame and the X member would make it a lot better than the stock convertible frame.
dvap has at least 4 55 98 4door hardtops, im sure they would sell you a frame. id bet there isnt to much modifications between a 4 door hardtop and rag top frame. or at least less then modifing a buick frame to fit. also the 98 is 11 inches longer then the 88 so i doubt a buick special frame is going to work unless you wanted to make a super 88 conv. which is shorter, or add some lenght to the buick chassis. 55-56 olds frames are pretty much the same except 55 didnt have dual exhaust. 56 did, the difference is in the x member is missing a hole on a 55 and the gas tank is different. hope this kinda helps you. good luck sounds like a fun project....john
Hello, In looking at the two similar, but different GM cars. They are cousins from the same family and have similar styling cues. GM was well known to share designs within the whole GM family. But, it all comes down to individual tastes. The Buick had more power, but the Oldsmobile had the wonderful Hydramatic transmission. So, one gives and takes. Having driven in a lot of GM cars (from 51 Oldsmobile to 55-56 Chevy sedans, a 58 Impala and then 65 El Camino) with and without coil rear springs, for me, leaf springs just does not cut it for a smooth road worthy sedan, this time, the Buick takes it in style and handling. The hardtops look stylish with the windows rolled down, then it comes down to the swoopy accessory design of the Buick versus the rocket tail lights of the Oldsmobile. My dad had his share of Buicks (every 4 years) from 1941 up to 1982. Those were nice big family cars and only one version of the big Buicks had some styling advantages with those cool wire wheels. A custom touch straight from the factory showroom floor. Our mom wanted a 54 Buick Skylark convertible with those cool wire wheels. My dad nixed it and bought a 57 Buick 2 door Roadmaster sedan as his next car. It is hard to differentiate between the two. For the most part, the ordinary Joe/Josephine would see each model and say what a cool old sedan it was. It is the idea of an old car in good condition that draws the eye on the road, car shows, plus weekend Cars and Coffee events, even during the pandemic. Jnaki So, the comparisons will always be similar due to the fact that they came from the same styling family builder. GM. In our teenage cruising/hot rod world of this time period 1955-63, for us, the Buick had it over the Oldsmobile sedans.
I can see you've been searching for a long time. And have lots of bad information. The Chevy X member won't work without a bunch of cutting and welding. LOTS. And it still may not work right, the Olds is a longer wheelbase, and the 98 even longer. Your best bet is a 98 4 door chassis. You may or may not want to beef it up. It already has an X frame. You can add some extra metal if you like. I boxed my chassis on my 88 hardtop frame, both for extra strength (running a 455 and turbo 400) and for the fact that the car sat low, and the bottom part of the frame was waffled. Straightened it out and added a 6 inch (IIRC) piece of 1/8" plate to it. Not a big deal.
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