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Thread: 1956 buick special 322 nailhead to 1976 bop th400

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    1956 buick special 322 nailhead to 1976 bop th400

    hello i wanna keep my sweet 322 nail head but would to install a super awesome th400 out of an electra. i have an adapter for bop to chev. what else. cant seem to find anything on this combo. please help thnx james in chattanooga tn

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    You will need to get an adaptor like this:
    http://www.transmissionadapters.com/...ad_install.htm

    Your Chev-to-BOP adaptor plate gets sandwiched between the Bendtsen's adaptor and the transmission. Do you already have the details of the open drive conversion sorted out?

    Ray
    Last edited by raycow; 08-15-2012 at 07:58 PM.

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    no i dont really know all that is implied with this conversion. ive been reading on it for days. my special is a 4 dr hrdtp. but still a great old buick and would like to make it a daily driver. all info appreciated thnx james

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    Quote Originally Posted by james1956special View Post
    no i dont really know all that is implied with this conversion. ive been reading on it for days......all info appreciated thnx james
    As you may already know, the driveshaft on your Buick (and other Buicks up to 1960) is enclosed in a "torque tube" which connects the rear axle to the transmission. This tube is part of the rear suspension design and performs two essential functions. First, It resists the rear axle torque reaction (when power is applied, the axle housing wants to rotate in the opposite direction to the wheels). Second, it transmits the rear axle driving thrust to the frame by means of the thrust pad mounted on the transmission crossmember. The axle is pushing on the torque tube when you are driving forward and pulling on it in reverse. At full throttle in 1st gear, this thrust can amount to more than a ton, assuming the rear tires can get sufficient traction.

    If you want to run any transmission other than a Dynaflow or a stock manual, you no longer have a way to connect the torque tube to the transmission. This means you must now convert to open drive and replace the rear suspension with a design which can perform the same functions that the torque tube used to do.

    The most commonly used arrangements for this are 4-link, ladder bars, and "truck arms". Truck arms are called that because most people are familiar with the design used on 60-72 Chevy half ton trucks. However, the same basic design was also used on Oldsmobiles up to about 1950 and possibly other cars before that. With most of these designs you will keep the existing panhard bar, which is a crosswise link that locates the axle from side to side (look under your car and you will see it just behind the axle). At least one type of 4-link design does away with the panhard. You can see this on GM A-body cars from the 60s and 70s.

    I won't get into the debate of which design is better because most builders have their own preferences, and an opinion is an opinion. If cost is a concern, truck arms will likely be the least expensive, because these Chevy trucks are still fairly easy to find in salvage yards (don't bother looking for the Oldsmobiles though). Truck arms are also available from aftermarket vendors if you want all new parts, but then the cost will be about the same as the other designs.

    Because you are fortunate enough to have a 56, the one point I will take a stand on is, keep your present rear axle. This is because 56 was the first year for the axle design which was used until about 65. These were open drive from 61 on, and the center sections from those will bolt into your present axle housing without modification. First choice would be a 61-62 chunk because those have the same shaft splines as your 56. Later years can also be used, but then you will have to swap the side gears to match the splines on your shafts. The reason I am raving on about this is that you get to keep your stock brakes and you avoid the hassle of cobbling your parking brake cables to work with the brakes that come with a different axle. This can be a much bigger annoyance than you might think.

    Ok, I know I have babbled too long already, so I will shut up now. If you have any questions, please feel free to ask.

    Ray
    Last edited by raycow; 08-17-2012 at 05:06 AM.

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    good night alive!!! this is just what i was looking for. great info and ideas! im gonna try to keep my dynaflow from pouring fluid till i get my parts gathered up. any thots on what to do first? thnks again ray
    james

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    Quote Originally Posted by james1956special View Post
    any thots on what to do first?
    Well, first you will need to decide on what type of suspension you want to go with. I have done only one open drive conversion on a Buick and I used truck arms from a real truck, so I can't speak to the merits of the other systems out there or the vendors who sell parts for them.

    You might want to post on the suspension and driveline forums to get input from other members. Just from reading the posts, I would say there are a good number of people here who have converted to open drive. You could also do a Google search to get some vendor names and look at their offerings, and maybe find some reviews or magazine write-ups.

    You will also need some used parts, like the rear axle center section, no matter which system you settle on. These parts might take the longest to find, so check out your local salvage yards and also ebay, craigslist, and any other venues in your area where used parts are sold. For example, there are "newspapers" which are made up entirely of classified ads. In the worst case, you may need to go outside your local area. There are used parts souces online which will ship anywhere, but anything heavy can get expensive by the time it arrives at your door. If you have a truck or trailer it might be cheaper to pick up the parts yourself.

    Lastly, if you don't feel up to doing all of the work yourself, you might want to check out some shops which do custom work for performance modifications. At the very least, plan on getting some welding done, as I haven't seen any suspension swaps yet that are totally a bolt-in. You also may need the services of a driveshaft shop.

    That's all I can think of for now. Perhaps others might catch something I could have missed.

    Ray

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    I myself would keep it all Buick. If you put your '56 on the lift & next to it put a '61-'65 Full size or a '63-'70 Riv. on the lift next to it you will see that everything from the donor car will be there that you need. Do some careful measuring & swap out brackets & other needed parts as nec. The engineering has already been done by Buick & all you will be doing is making a mirror image of what is being removed. The added advantage is you will be maintaining the 12" brakes that the '56 already has. You could try designing your own set-up, upgrading brakes, along with the engineering & learning curve nec. to accomplish the proper engineering nec. for suspension travel, geometry, etc. But IMHO why bother when it's already been done & proven.
    Just my thoughts on the subject.
    Tom Telesco
    Classic and Muscle Automotive
    12 Cook St.
    Norwalk, CT 06853-1601
    Day Phone 203-324-6045 ET
    NailHead Mini-Starters '53-'66
    Adjustable Roller Tip Rocker Arms - All NailHeads
    Custom forged pistons
    Front & rear neoprene seals
    Many other "Nail" parts
    "If I can't get it, you don't need it!"

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