I found what appears to be an LS6 block. Casting number 3963512, dated K 11 9, 4 bolt main. The confusing thing is the deck is stamped with a CPA code which I believe is from a 71 4 speed car. Would GM, in anyone's opinion, happen to use a left over extra block with a 69 date code in a 71 Chevelle? It does not appear that this block has been restamped or decked. It's been bored 30 over. Next opinion, assuming this block is fine, what's it worth?

opinion ?
OK, I seriously think there would never have been a 69 date coded block in a 71 car.
Casting number does show 1970-1976 454

CPA was used in 1972 Chevelle 454 270 Manual 4bbl
and 1971 Monte Carlo 454 365 Manual 4bbl

I don't see any LS6 engines with the CPA code, where did you find that?

IF it had the correct numbers and code for a 70 LS6 it would probably bring 3 or 4 k to someone with a 70 Malibu 307 convertible smile.gif

OK, checked three different source books and all concur that the 512 block was used only in 70 and 71. The CPA code was used in both 71 and 72 Chevelles. Also, when GM anticipated a strike they stock piled parts. If that were the case, would it be all that odd to see a late 69 block used 8 or 9 months out on an early production 71 car? Come on guys, bring it on!

If that engine was an assembly line installation then there will be a VIN derivative stamped on the pad also, e.g 10K123456 etc. If there is no VIN derivative, then it was not installed in a car at the factory. How it came to be what it is today is open to anyones guess.

I am sure some will chime in and say they have seen them without an VIN but that was federally mandated it have it and the chance a car left the plant without it are slim to none.

Forrest, Your three source books are wrong about the 512 block being a 1970-71 item! That block may have started life on the drawing board as a 1970 production year 454 but there were in fact thousands of 1969 Corvettes/Chevrolets/COPO's that used that block as a 427 in 335, 390, 400, 425, 430 and 435HP configurations. The earliest date code 512 block I have seen is A-22-9, T0129LM, 19S719724, 3rd week of March 1969 build date 1969 Corvette.

most people I have talked to who claim to "be in the know" will say that is is very possible that this was in a 71 even though cast in 69. First of all it is a late 69 cast and they would have been assemling 71 models late in 1970. All the "numbers" people get all hung up on having dates w/n a certain time period but the real world did not always work that way. Also, parts weren't wasted, they were used up. Bottom line, if it is stamped CPA it ain't an LS6 block.

Hi Dave. I have a K68 [Nov 68] casting #512 block, and also an L70[dec 70 for 71 production]...#512 was used in 1969 1970 and 1971 production ...#289 came in for 1972 and on//....1971 Ls6 corvettes were the only ones to use a 4 Bolt block after 1970...

Originally posted by freshayr:
Bottom line, if it is stamped CPA it ain't an LS6 block. Correct, however if you have the block decked removing all traces of the assembly and useage codes and sell it accordingly you WILL get LS6/L72 type money for the block. Highly desireable block.

Rick, my guess is someone already decked the block and stamped it to match a 2 bolt application not knowing what they were doing.Its unlikely to be a factory piece dated so long before assembly date[that is assuming someone converted it to 4 bolt and the stamping and time frame between casting and stamping was legit]... a factory 4 bolt would not have a factory cpa stamp on it.....

1st of all, I have to say there is a wealth of information here at Team Chevelle. Without you guys some of us would not know a whole lot and I'd like to thank all. Anyway, here's the scoop on this block. I took it to a machinist today and the block pad had been planed and restamped. Evidently I do have a 70 LS6 block.

GEEZ,I AM GOOD..........