Help end debate on Frames

[Guest kevinshea]

I am trying to get definitive information on any real differences between convertible and non-convertible frames. people suggest that they are different but all the data that I have doesn't. I am particularly interested in 54-55-56 vintage.

The argument is that the X frame pieces are thicker or wider. I have measured the top flat piece and it is 6 X 6 3/8" thick. If you have a frame that you can measure, what do you have and what is the corresponding measurements on the top plate. ???

or if you have any Buick service material that notes specific differences, can you post it?

[The Old Guy]

I don't know about the 50s frames, but the 40s Buicks used thicker metal. My 40 was stamped from metal .030 thicker than the sedans

[Guest imported_bjr]

In the 54 shop manual it says the small series cars use the same frame for the coupes and converts, different frames for the large series coupes and converts.

[old-tank]

The frame of my 55 Century CVT is thicker in the center "X" section only.

[NTX5467]

Please be cognizant that when chasing things like this with any kind of parts book, that it might well indicate a "different" frame for closed or open vehicles, yet they'd all probably bolt onto the same body structure and work just fine. That would indicate a common architecture such that production and assembly costs would be decreased somewhat.

How would they be different? The thicker gauge metal would be one, just as the thicker section in the middle would be another. Even one extra drilled hole in the metal would generate a complete different part number--unless they standardized that "extra hole" frame into the other production vehicles of that type. Sometimes, if that extra hole (and related labor operation to drill it) makes that particular frame cost something like an extra 25 cents to do it, then it might only see limited use on models that absolutely require that extra hole to be there, rather than spending that money on all of the frames like that. To us, the 25 cents would not be significant, but when you consider 400,000 25 cents . . . it can add up quick. Or they could put a frame under the car that was already strong enough to tolerate the car not having a roof and expect to see the economies of scale orientation kick in. All things which relate to just what the car costs to get to the end of the assembly line versus profits from the sale of the vehicle at a particular competitive price point.

In general, the open cars would most probably need some extra gussets and such, plus thicker metal in certain places, and possibly some extra cross braces. None of these things would relate to the basic dimensions of the frame (as you'd find in a body shop frame manual or GM Buick Chassis Manual that had the checking diagonal measurements to use for frame squareness considerations) for a particular vehicle. In some cases, there might also be actual stamp numbers on the frame rails somewhere, or painted ID numbers on the frame rails, that could help identify the item on the assembly line. Identifiers that would hopefully still be there at this point in time.

Also, in dealing with the GM parts listings for the vehicle, they could have used a particular frame on the assembly line, but if it came time to replace the frame (for whatever reason), it would be replaced by a "service" frame that could well "go everywhere" rather than on just one particular model that year. It could be "police spec", for example, if that model had a HD or police car option available that year.

Just some thougts,

NTX5467

[Guest kevinshea]

Sounds like you work for the car companies, since everything you say is correct!. Frames that have an extra hole or gusset, such as the convertible, would show up as a different frame part number.. and costs are the deciding factor

I have noted frame "differences" with my Ford restoration as well.. From 35-40 same frame but with different brackets.. thus same but different, but not in the frame construction.

My issue comes right down to the frame section and plate thickness(es). People here do suggest that the frame gage are different, but I am trying to get actual data, i.e. measurements off of different cars. I can provide all the measurements from the 54 convertible, but do not have access to closed cars frame(yet).

I understand that a thicker frame could provide added torsional stiffness, that may be necessary for convertibles. So it may make sense from the engineering side. But, no definitive data on thickness exists in the shop books that I have.

Can someone help with calipered measurements from a closed car frame?

[Bhigdog]

The most important thing to understand here is that Kevin and I have a bottle of wine (or "whine" to the loser) riding on this issue. I say, from actual observation, that the convert. X member is MUCH thicker than the corresponding closed body frame. At least in 55 small body series..........Bob

[Guest kevinshea]

Well Bob -- things may be looking up for you. I had the opportunity to get under a 54 2 dr sedan the other day and measured the X plate with my sensitive finger ( a truly great gage)... I couldn't get the caliper on it though.

It really felt like 1/4" thick as opposed to the 3/8" measured plate on my convert.

Still holding out for real measurements, but you can start wetting your whistle.

[Bhigdog]

I would say those thicknesses sound about right. I can still measure the X member of the 55 Riv. I cut up if you want. But it would be a 55 not 54. My throat is kind of parched, now that you mention. 8-).

[Guest 1964 225 Roadster]

Ask MrEarl, he hasn't responded here. He has about a dozen 54's.

[Bhigdog]

The 55 Olds has basically the same X member type frame. The frame on my 2 door Olds closed body measures only .140 thick for all sections except the X member web which measures only .070. I could tell working on the olds that it is of less quality than the Buicks. The frame probably weighs half what the Buick does. Does any one know the 0 to 60 times of a 55 Olds Super 88 vs a 55 Buick century? They both have close to the same C.I. but Buick claims 34 more horsepower. The Olds claims more torque at a lower RPM. My guess is the olds would kick [@!#!$].

[Guest imported_MrEarl]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Ask MrEarl, he hasn't responded here. He has about a dozen 54's. </div></div>

Sorry, Skylarks and verts are out of my league.

Kevin, didn't I already quote something in a email to you regarding this that I had dug up from a manual back about a year ago. I believe it was that it is thicker but what guage, I don't know.

[Guest kevinshea]

yuh -- we talk off frames but it was mostly about overall dimensions -- have you received my emails? ended up with a bunch of hood insulation roads and disks.