1955 Engine into a 1956 Packard

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glde7459
Posts: 1
Joined: Sat Dec 26, 2020 7:41 pm

1955 Engine into a 1956 Packard

Post by glde7459 » Sat May 22, 2021 12:15 pm

I was fortunate to purchase a 1956 Patrician that is in excellent condition with the exception of the 374 engine. it was frozen. it was taken apart and the #5 cylinder wall is in bad shape. I just was able to purchase a 1955 Four Hundred with a fine running 352. What will it take to transplant that engine into the 56? How does one go about doing the conversion from a 12 volt positive ground system to a 12 volt negative ground system. I do have an idea about changing over all electricals from the 374 enging to the 352 engine inclusive of the coil, distributor, generator and starter. Any suggestions from the group? Thank you. :)

Howard56
Posts: 1301
Joined: Mon Dec 24, 2012 11:35 am

Re: 1955 Engine into a 1956 Packard

Post by Howard56 » Sat May 22, 2021 1:27 pm

Engine will bolt right in and a polarity change will not be much of an issue. For appearance sake you might want to change the engine color from the 55 colors to the correct 56 Bronze block with Silver rocker covers as used in the Patrician.

The 56 is already negative ground so if the 55 coil is used it will still work but that would be the only thing that would need to have the wires swapped to maintain best efficiency. If you were changing a 55 car to negative ground the coil will work but for the reason given the wires should be reversed so the negative terminal on the coil goes to the distributor. The generator would need to be repolarized and there is a question on if the voltage regulator would need to change. Some voltage regulators are designated positive or negative ground but there have been no documented differences posted in forums so we are not entirely sure what might be different to give them a specific designation. Speculation has it that the contact material might be the difference so as to have the contact side prone to the heaviest arc being made of a material less prone to pitting and melting. The reversed original regulator may have life shortened if that is the case because the arcing would then be directed toward the weaker contact.

You would need to change the wires on the ammeter so it will read properly but other than that a stock car should need nothing else. If the car has anything solid state such as a modern solid state radio vibrator replacement, that will be an issue as possibly could be a modern solid state rework of the torsion level control switch. If both are stock then nothing else to worry about. All the motors are internally wound in such a way that they are polarity neutral.

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