Hello all. Just starting a new project, and thought I would join you for information. I have just purchased a 1966 Buick Electra 225. My first problem is ID of the big block. No ID numbers can be found on the motor, and I have been told by a few that pre 68 or 67 motors did not have ID numbers stamped on them. Any Distinguishing characteristics between the 401 and the 425? Thanks for all help.o No:
You didn't post this same question on the C&D forums, did you? I'd hate to give you the same post twice, especially since my last attempt appears to have not worked out for you.
Use this link to help you: http://www.buicks.net/shop/engine_ident.html . Look for the picture part way down the page that has All Nailheads 57-66. The picture shows the location of the production code. The production code tells you the engine year, size and type. Match the code on the passenger side of the valley pan rail on your engine to the engine codes on the right side of the page. My guess is that it will be an MT: 1966, 401 or MW: 1966, 425. There is a casting #s link on the bottom of that page that may help if you can not figure it out from the production codes, but some 401 and 425 casting #s are shared. Lastly, the bore will tell you what size it is if you tear it down. Good Luck! Cheryl
