CMT 350 block (SBC)?

[85 Cutlass Brougham]

I never decoded by block before, but for some reason, decided 2:45am was as good a time as any to read it. It is stamped ( deck behind alternator) CMT. What did this 350 come from when new? It seems to be a 1974 block from what I read online, but now I wonder if it is a 4 bolt as it supposedly had 245hp when new, which makes me think of the last year LT-1 from a Z-28, which would mean a 4 bolt block. The confusion comes from the machine shop guy who built the engine and supplied the core who said it was a 1977 2 bolt 350. So, if you have a decoder book, I would be curious as to what it says. Thanks!

 

[robnoxiousauto]

the numbers you need are from the back of the engine block on the left side beside the dist. if they are 3970010 or 3970019 they will be the very common two peice rear seal sbc 350 and either of these numbers can be 2 or 4 bolt mains good luck

 

[85 Cutlass Brougham]

Number pulled, and yeah, it's a 3970010. It basically tells me nothing but that it could be a 2 or 4 bolt 350 2 piece seal block ( I already knew that as I had the heads off last year). The CMT could also be a B body 350 2 bolt main 170hp ( LM1?) vs the L82 in the Z-28. It seems to have come from an automatic car, but that does not rule out a Z-28 as automatics were available starting in 73 or 74 (can't remember which). I guess I will have to pull the VIN off the block from the front pad tomorrow and try to decode it. BTW, I found an excellent decoder tool at:http://www.73-87.com/chevy_ids/sbcid2.htm which I am using to work out the mystery. Hope it helps someone else with the same curious question.

I do tend to think it's a lo-po 2 bolt from a Caprice or Impala, but would not be mad if I got a 4 bolt block for the price of a 2 bolt either. It does have a cast crank and rods though, so RPM's are limited ( I specked it this was because it was originally used for pizza delivery, and I considered the short block a throw away item when it was done in 1996). Who knows? Maybe I'll destroke it to a 327 one day and take advantage of the better block if I have it.

 

[Coveted]

1974 CMT 350 t4OO L82 245 4 Camaro/Chevy II
1978 CMT 350 LM1 L 170 4 B


its more than likely a late 70s 2blt 350.
I have one of these blocks, well minus the cmt part
the rear number is the same.
funny you use the same site as me to decode.

 

[85 Cutlass Brougham]

I actually just found that site. It's pretty complete and saves me the money of buying an actual decoder book. Google to the rescue once again!

One curious thing about this whole issue is the 2 and 4 bolt engines used the same block casting. I had always been told the 2 bolt blocks had stronger webbing in the mains. It would seem though that the only difference was the number of main cap bolt holes that were drilled and tapped. I was actually thinking about Milodon main caps to convert to 4 bolts as the splayed design is stronger than GM's straight down, and supposedly only a 2 bolt block could accommodate it. For now, I am just happy that it runs as I have too much on my plate to build a new engine. Plus, I have not finished figuring out how I would do it to best reach a compromise between driveability and power.

 

[robnoxiousauto]

I will only use two bolt main blocks for my various engines so that I can install splayed main caps. If the engine you have is rebuilt then the cmt on the front of the block no longer matters unless you still have the original pistons still in there and the original heads aswell. The chances of the block being a high nickel on are very slimm with the 0010 casting. Just be happy it runs for now till you can turn it into something retarded.

 

[bowtie81]

i called chevy land there in the back of the car craft mag. i gave them the numbers off one of my blocks and they told me exactly what it came out of.

 

[bowtie81]

the 2 bolt 400 sbc was stronger in the webbing on the mains. but the 350's are equal.

 

[megaladon6]

my block, which is a high nickel content, has the 010 and 20 seperate from the casting number.