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56 Buick Special, SBC350/TH350 swap


Guest Rohrbach84

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Guest Rohrbach84

What can be done with the torque tube driveshaft and rearend with this swap? Doing it for a buddy but not so sure we want to replace all that. Can a person get a bellhousing adapter and just put in the 350? He said it has a nailhead that's 200something ci. I'm not to keen on these cars. Let me know, thanks!!

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 A '56 should have a 322 ci.  And that is a GOOD engine. My brother had a '56 Special in '58, and none of the Plymouth Furys of that time could stay with him. 

 

  There are adapters to attach the tranny to the Buick engine, but not to attach the tranny to the torque tube that I am aware of. Changing transmission will probably require changing the rear end. Gets to be a lot of work. 

 

  Ben

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Keep in mind that the Special has a 3.23 rear axle ratio.  The Century has a 3.36 ratio, and the entire axle driveshaft unit is interchangeable into the Special.  My Super also has the 3.36 ratio and runs in the 14-15 MPG range so the Special should do a bit better without sacrificing off the line performance.

Edited by JohnD1956 (see edit history)
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Google Hot rods to hell HTH.com they offer rear end kits for Buicks. If you've ever seen the rear suspension on a Winston Cup race car, it is almost identical to Buicks design configuration! It is comprised, surprisingly, of trailing arms from coil sprung trucks 64-72 from GM's other devisions(Chv/GMC)! You might be amazed how simple this looks. The reason Buick and GMs truck devision and the Winston cup folks used this system is be cuz the longer the rear control arms are the better the rear suspension works in terms of handling. The brake drum moves not straight up and down when it goes over a bump or into a dip on the road. It forms an arc like this ), with the midpoint of the arc being the "static" or stopped position of the center of the rear brake drum. If you were to measure it,closer to front of car at top or bottom of arc, you can then understand that it would become an axle that is steering the car from the rear with this motion. That makes going Through a corner much less predictable/ manageable. The shorter the connecting trailing arm, the tighter the arc, the more the rear axle moves forward and back, as it cycles up and down from bumps or simply body lean in a corner. Many folks advocate four short arms like my '64 and '72 Specials and Skylark use this is not optimal for handling, but a compromise for other agendas, cost effective, exhaust routing, or whatever. These are not my engineering ideas, but research from Winston cup design, Mark Ortiz suspension monthly newsletters, free for signing in at his website and other readings. There are a lot of reasons why folks choose one system or another, but my motivation is safe operation as my priority, so I vote for this design! Good luck with whatever you choose and I hope I at least gave a little food for thought. Greg

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Somewhere back in the archives of the "Me and My Buick" I have a 55 special that got a rear from a granada I think?  Anyhow, we made trailing arms based off the 67-72 c10, had a 700r4 and a 6.2 diesel.  I never finished that project, but anything is possible!   Right now in Charlotte, NC there is a decent 322 with dynaflow for $800 if you wanted to go bolt-in.

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Knowing that Olds used an open driveshaft with rear leaf springs, I'm curious jus how close that spring/axle assembly might be to fitting the Buick chassis??? Leaf springs wound not need any of the additional axle-locating links/devices which a coil spring rear suspension needs, which should simplify things.  That, plus a custom-made driveshaft, might work?

 

NTX5467

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I did a Google search for "1955 Buick Olds" and found a comparison article from Hemmings Classic Car magazine. A '55 Century convertible and a '56 Olds 88 convertible, both belonging to a west coast BCA member.  The article was a comparison of both cars, which were very similar, spec-wise, AND as the article stated, were on the SAME 122" wheelbase frame.  IF that's indeed the case, the Olds rear suspension items should be easily-adapted to the Buick, I suspect.  Only item which had something different was the rear track on the Olds was 1" narrower than the Buick's rear track.

 

Now, what this means . . . is that with the many sources for "particular specification/suspension configuration" versions of the Ford 9" rear axle, one could be built with the same rear track as the Buick, possibly even for rear disc brakes . . . OR if a production 9" could be found with the correct rear track, a salvage yard search might be appropriate (and possibly less money!).  Knowing the specs on the Olds rear leaf springs, then a new set can be built and interfaced with the 9" Ford rear axle tubes.  Then, all that would be needed would be the front spring-eye hangers and the rear spring shackles.  Nothing that a drag race chassis race shop couldn't do.

 

Others have any thoughts or experiences??

 

NTX5467

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Guest Rohrbach84

Thanks for all the input! I'm doing this for a buddy that like most wants to keep it cheap and simple. He had this rear end and brakes all gone through so doesn't want to mess with that. We are thinking at this point to leave the transmission that's in the car. Who makes an adapter to go from that trans to a 350 Chevy engine? What trans is in this car?

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There are adapters for the Chevy transmission's bellhousing to the nailhead engine but there's nothing to do the opposite.  Find a larger 401/425 engine and the dynaflow from a 57 - 59.  That trans will have the smaller diameter bellhousing of the 401/425, but will be equipped for a torque tube.  As long as you keep the torque tube, you're stuck with the dynaflow.  The 401/425 from '64 - '66 came with a TH400.  Or you can bolt an o/d trans to the nailhead, but you're going to have to do something with that torque tube rear end.

 

Ed

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