1970 and 1971 Z28 winters intake letter stamp meaning?
 

I have noticed on several 1970 Z28 #110 casting intakes and 1971 Z28 #594 casting intakes a letter stamp on the driver side center top of the intake near the base of intake. Was this letter only stamped on intakes used for warranty replacement to denote the month intake was put into service? Example: single letter "J" Would that be J for September? Anyone shed some light on this?

Seen this asked before on NastyZ28.
No good answer I have seen. It is on my original intake, but is I think its a number. No correspondence to a date. My guess is that due to it being a stamp and not a casting that it is done post molding and relates to a machining operation. Probably not warranty replacement. I've seen it on too many engines. Unless they replaced many intakes and I think we would have heard about that.

That was me asking over at NastyZ28 as well never did get an answer.

Looking through my photos this is a shot of Mark M's 70 Z28 which was 98% original when I got it and this was stamped on the intake. I blew it up and cannot really make out for sure what it was. An "A" or backwards "4" based on when I blew up the photo. The engine assembly date was 3/11/70 so maybe it is an A? This stamp looks much larger than yours however.

I have seen mostly letters by themselves. That appears to be an "A" to me. but I have seen numbers as well. I remember seeing a "70" stamped on a 1970 #110 casting intake. Just trying to determine if there is any correlation between casting date and these stamps?? Just curious why most intakes have nothing yet some have these stamps?

That is a GM receipt quality audit stamp. Winters direct shipped so each plant did a quality audit on a segment of each batch of manifolds to verify the contract production specification prior to assembly.

FWIW, "J" would be October. "I" would be September.