I just bought a 38 Buick Coupe and it's got the 248 straight 8 engine. I'll leave the 248 in it for a while but my intentions are to transplant a healthy 401 nailhead and switch pitch 400 transmission. Unfortunately the 38 is the first year of coil spring rear suspension which makes swapping out the rear end a whole lot more difficult than the 37 which had leaf springs. Watch the best way to go about getting an open drive rear end in the car?
I am doing the same in my 40. If you want to keep the 5 on 5 bolt pattern, a 58 Edsel big car rear is the right width at 59". If not concerned about the wheel BC, any rear in the 57-59" range will work. 99 Explorer 8.8 rear is the right width and has discs. Because of the rear coil springs and frame design, there are limited options- GM truck arms, parallel arms, or triangular arms. I opted for the GM truck arms. The stock arms are a little long unless you cut part of the X-bracing on the frame out, so I shortened my arms 3". A fabricated front arm mount is required. I copied a design from another member. Since the springs mount slightly behind the centerline of the axle, a fabricated adapter that sandwiches between the arms and axle perches works. I can offer some more insights if you PM me.
Thanks for the reply. I've seen where some center sections will swap out and eliminate the torque tube requirement but I'm sure those are getting harder and harder to find. I like the idea of the trailing arm suspension from the 67 to 72 Chevrolet half ton trucks. I saw on YouTube where there was a kit sold by Centerville to convert to 40 and up coupes. That kid came with a cross member for the trailing arm pivot points
You can use the half ton front pivot point crossmember if you remove part of the x-member. I didn't want to do that, hence the fabricated bracket and shortened arms. I too am installing a healthy 401 in one of my coupes. Just a regular Th400 behind it. Buicks used the torque tube rear axle up thru 60 . Unless you are going to run headers, start looking for a set of 61 LaSabre 364 single exhaust manifolds. They dump in the right spots to miss the steering box.
Does this swap require a center sump oil pan or a rear sump pan? I have a rear sump but the centers are pretty easy to come by
A rear sump gives more flexibility in where the engine sits, but the center sump used in the later 401s will clear the tie-rod if the engine is back far enough. Is your car a Special or Century? Supers came out in 1940. Early 401s had the rear sump pan and pumps, later ones center sump and pumps.
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