Crate Engine Identification

[C10_Blackie]

Hi all - I have a 1981 C10 that I bought a couple of years ago and have been slowly working on ever since. I know it originally had a 305 SBC engine and believe that it now likely has a 350 SBC crate motor. The previous owner said he thought the motor was installed about 20K miles ago by a different previous owner but I kind of doubt that (the guy I bought it from seems to have a loose relationship with the truth and there was no documentation to go along with it). The carb that is on it was built in 2002, and my guess is that it was installed at the same time the engine was installed. The headers have a good deal of external corrosion as well and is consistent with the swap having been done 20 years ago. But these are just assumptions.

I got a peek a while back at the casting numbers but they were covered in gunk from a head gasket leak that I corrected and it is really hard to get a clear look back there. I'm going to try to clean it up and get a view over the next few days but I'm pretty sure it is one of those "GM" prefixed casting numbers they used on crate motors out of Mexico and don't really tell you much.

Anyways, I've attached a clear pic of the stamping numbers and was wondering if anybody could tell me more about them or verify any of my guesses. I read it as "1M0830 1H04". Best I can figure is that the "1" means Chevy, the "M" means Mexico and the "0830" is month and day. What the "1H04" could be is beyond me and I couldn't come up with anything in web searches.

I get that this may not tell me much, but it could be nice to know. Obviously, I won't know what I have or how it is cammed unless I tear into it and take measurements, and I'm not likely to do that unless something goes really wrong.

Thanks!

 

[Hilllbilly]

cast numbers is how I ID cheby stuff

Its gonna be light weight, thin wall casting though

 

[BillK]

That stamping number does not look like a factory number, at least not one I remember seeing. It could be from a rebuilder like Jasper etc. I have several late model blocks at the shop and I will take a look Monday to be sure.
The casting number at the back will at least tell you which block it is and what size the engine probably is. Post a picture of the front of one of the heads too.

 

[goldpack]

M = Mexico ? ???
my own original 1986 3/4 ton's 350, has the factory designation as a M engine.
and sorry to link Wikipedia for such ....which can suck

Chevrolet small-block engine (first- and second-generation) - Wikipedia

en.wikipedia.org

cut and pasted off that wikipedia page

LT9​

Years: 1981–1986[21]

The LT9 served as GM's heavy-duty (over 8,500 lb (3,856 kg) GVWR) emissions[22] variant of the 5.7 L (350 cu in). It was used in C/K 20/30 pickups, G30 passenger and cargo vans (built in Lordstown, OH, and later in Flint, MI), and P30 chassis used for motorhomes and step vans.

The LT9's listed specifications are 160 hp (119 kW) at 3,800 rpm and 250 lb⋅ft (339 N⋅m) of torque at 2,800 rpm with 8.3:1 compression.[23] LT9 engines were carbureted with Rochester Quadrajets from the factory and generally have four-bolt mains. The LT9 is often known as the "M-code 350," from the eighth character of the VIN.[22]

 

[C10_Blackie]

That stamping number does not look like a factory number, at least not one I remember seeing. It could be from a rebuilder like Jasper etc. I have several late model blocks at the shop and I will take a look Monday to be sure.
The casting number at the back will at least tell you which block it is and what size the engine probably is. Post a picture of the front of one of the heads too.

Thanks. I'll try to take a few pics when the weather clears. I've been dealing with some strange electrical issues so am going to be occupied with that until I get it.