The Stovebolt Site Forums The Shop Area Engine Shop Decoding V8 Block & Casting Numbers?

HELP, PLEASE,
3 different "decoding sites" give me 3 different non-definitive answers for this small block Chevy block with a date code: D 22 8 !!! One says it might be a 68-327 or 69-80 400HP police 350, could be 2 or 4 bolt mains. Another says it could be 350 or 305. Another says......... :confused:
Here are the #s:
>Left rear of block just in front of bell housing:3970010
>Right front below the head: V0513CMJ & 16J295220

Even the local machine shop tells me that all he can say is that it's a 350 from the left rear "casting number" and that the other numbers don't tell him anything, like 2 or 4 bolt mains or cast or steel crank. Any help would be greatly appreciated.
Thanks,
Gene & Jr

this motor,from what you tell me is a 75 350 2 bolt main 145 hp L-65 impala and chevelle 2 bbl. nobodys journal is exactly perfect on this matter and you would think gm would have kept better track but they didnt.the only way to know for sure if its 4 bolt main is to pull the pan.and if your machinist is no more familiar with the small block chevy i dont think id trust him to machine it.

According to most sources, the 3970010 casting was used for '68 327, and '69-'79 or '80 350 engines, and possibly one year for a 302, but not the 305, which has a different bore.

Two numbers don't add up here. Assuming a 350, which didn't come out until '69, the block date code would be from '78, but the second digit of the VIN code (6) suggests '76. Could the 8 in the block date code really be a 6?

The engine build date of May 13 seems like a close enough fit with the block casting date of April 22.

Sources show the CMJ suffix as a '74 police 350 4-bolt main (or an '80 Camaro/full size 305, which doesn't apply here). '74 doesn't match the VIN year (or casting year), but I suppose it's possible that the suffix carried over to '76 without the sources showing it.

The only definitive thing the numbers tell us in this case is that this is a 350 block. Internal details would have to be determined by inspection.

The number in front of the head on passenger side will tell you what it is any salvage yard should have the book to decode it.

My book says it is a 1967,283,PG,2 bbl.used in a Camaro.

Sorry about that last post,didnt notice the C.With the CMJ it comes up as one of two engines.First It could be a 1974 to 1976 350 Police engine,with 4 bbl.Second it could be a 1980 305 from a Camaro.The same suffix was used for both of these engines.

Virtually all the 4-bolt main bearing engines have a letter code suffix to the stamped number at the front of the block beginning with a "T". I scavenge wrecking yards all the time for core blocks with 4-bolt mains to build my roundtrack race engines, and I've found that virtually every one I find with a "T" in the suffix code is a 4-bolt.
Jerry

3970010 is a '69 - '80 350 or a '69 327 Industrial engine, or a '69 302 Z28 engine. Could be either a 2 or 4 bolt. The casting date is April 22, 1978. It cannot be older than that. I am 100% positive about that. Being a late 70's engine, I'd have to guess at it being a low perf 2 bolt "smog hog" motor, but there are exceptions. What are the head casting numbers? Pull off a valve cover and you'll see them.

Two bolt or four bolt, it really only matters if you are going for a full tilt Hipo build or plan on putting a blower on top. The "smog hog" motors do just fine with a good cam, cleaned up heads, good intake, right carburation, and 8.5:1 flat top pistons. More than enough there to put you back into the cushions when the foot goes down and still give decent mileage with the right rear gear. Don't walk away just because of the 2 bolt mains.

Here is the link to look your suffix code "CMJ"

http://www.nastyz28.com/sbchevy/spcode2.html

I have had lots of 2 bolt main hot rod motors and never had a problem.the number to go with is the one stamped in the block in front of the right (passenger side ) head.any salvage yard should have the decode book.to tell you what it means.all 4x4 pick ups 73 to 80 with 350 engine were 4 bolt blocks un less someone has changed it.