"M" date code on block

[Brandon Korman (28984)]

Have you guys ever heard of an "M" date code on a block? Someone told me he had an "M" dated 386 block, and I thought he made a mistake,because they only went to "L" (December). I've since seen a few advertised. Anyone know anything about this? Could an M-12-8 be made in January '69?

thanks in advance, Brandon

[Dennis Clark (7068)]

Re: "M" date code on block

I have not seen an M block or cylinder head.

[Mark Gorney (35760)]

Re: "M" date code on block

Brandon –

If it is a small block and cast in Saginaw, yes. In volume twenty-seven, number four, spring 2001, page 41 of The Corvette Restorer is an article by Gene Gamache addressing this casting anomaly. The “M” designation identified the castings (cylinder& case) as specials. The date tag was used for tracking the parts through processing. If the castings were approved by the customer (Flint), they were released into production and a few cases made it into Corvettes. Dan Pepper a member in Seattle has an "M" block in his '69 coupe.

Mark #35760

[Dennis Clark (7068)]

Mark, Now that you mention it...

... I did see one at a Chapter Judging event several years back. I ended up calling Terry McManmon while the car was being judged. Good thing he answered the phone and got us straightened out on the possibility of the "M"...

[Dan Pepper]

Re: "M" date code on block

As Mark mentioned, my '69 350/350 October build coupe has an "M" dated casing; "M48" to be exact. According to the article Mark mentions, these "special" blocks were cast in batches of 50 or so. A few from each "experimental" batch were cut-up for inspection. If the castings past muster, those remaining were released to the line. Let me know if you'd like any more info regarding my particular car.