can I replace a broken 401" engine, year 1963 (my car is a buick riviera from 1964) with 430 or 455 buick engine without changing the transmission? Or do I have to find a new 401 or 425 or else change the drive train.
Rob
PS I get many different answers when I ask around.


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You need another 401, 425.

63 has its own special i am a nailhead bolt pattern

The 64 has a ST-400 turbo and to use an earlier 401 will require some machining on the end of the crank, as the earlier engines had a Dynaflow ,and the crank flange is different. Using a 455 is a big job, and I would recommend rebuilding your original engineto save a LOT of grief.