Question for the K owners: C vs K engine suffix code question

[jocko]

I have a question for those of you with K10s and K20s out there. Below is a filtered excerpt of 72 350 truck suffix codes. Some indicate a K-only application while some indicate a C-only application. If there were no codes that indicated both C and K applications, I wouldn't have a question, but there are (like TDK, TFH, TFJ). So, I "would" have assumed that the K-only suffix code would have indicated to a line worker to install the correct exhaust manifolds, etc - the little bolt-on nuances of a K engine. But since there are some codes that apply to both C and K, I'm curious what the real differences are, if any, between a 72 C20 engine and 72 K20 engine.

Or put another way, what is the difference between a TDJ (C-only) and TDG (K-only) -coded 350?

Have any K owners that have original engines ever noted a C-only suffix code in their K (like a TDJ, TFD, etc)? (or vice versa)

My underlying assumption is that the engines are identical mechanically - and just have different bolt-on additions to make them specific to a C or K model - like the difference between exhaust manifolds on a C or K - but I'm curious if it's that simple - and the presence of codes that apply to both C and K muddy the waters.

For those of us with the purist ailment (and I fully appreciate none of these engines have partial VIN stamps), I am wondering if, for example, a TDJ or TFD coded engine could ever have been "correct" for a 72 K10/20. I'm pretty sure the answer is no, but I'm trying to figure out why that would be the case.
Something to chew on, thanks in advance for your thoughts.
I need to send up the Keith bat-signal...

[davischevy]

I have wondered about this for years. There is no combination of these codes that makes any sense to me. It seems that C and K, 10 and 20 and maybe AT and Manual would have sufficed.

[Keith Seymore]

I'm not sure we will be able to figure it out at this point.

Keep in mind those broadcast codes represent the part number level, so the changes could be pretty nuanced.

There could be a difference in compression ratio or 2 bolt vs 4 bolt main that we would have a hard time sussing out now. (For example, HD in the truck world means better durability - lower compression ratio and 4 bolt - not "high performance").

It also depends on how trimmed the engines when received at the vehicle assembly plant. For example, if there were distinctions in accessory drives: Power steering vs manual, A/C vs non, those would also drive proliferation. This is something that changed from year to year depending on the whims and motivations of the program team.

K

[jocko]

Thanks Keith, that's helpful info. I noticed some differences in the NastyZ28 suffix code references and the one posted here by IronCanine (Iron Canine's post at the link is from something a little more official than NastyZ28 (but I'm sure glad Nasty's website exists..) and it is less ambiguous than some of NastyZ28's info - for example, no "C or K" ambiguities, all those suffix codes are C-only or K-only (which makes a lot more sense to me) given the bolt-on differences like exhaust manifolds, etc).

But you raised a good point, something I didn't think of - how dressed engines were at arrival to the assembly line. When did the engine suffix code get stamped on the pad - at the engine plant or added at the assembly line once it was dressed out, etc? By the look of the pics above, they arrived with exhaust manifolds installed, which would lead me to believe the suffix code is stamped at the engine plant before shipping. So they truly did show up at the assembly line as a C or a K-specific engine. I guess... ha. Interesting stuff.

[tim71]

Those are really neat photos, thanks for posting. Bottom photo is interesting, you got guys in photo in a sport coat, in long sleeves, in short sleeves and the guy with no shirt.

[tim71]

oops, my bad, the guy has a shirt on, it just does'nt look like he has a shirt on.

[Keith Seymore]

Originally Posted by jocko

Thanks Keith, that's helpful info. I noticed some differences in the NastyZ28 suffix code references and the one posted here by IronCanine (Iron Canine's post at the link is from something a little more official than NastyZ28 (but I'm sure glad Nasty's website exists..) and it is less ambiguous than some of NastyZ28's info - for example, no "C or K" ambiguities, all those suffix codes are C-only or K-only (which makes a lot more sense to me) given the bolt-on differences like exhaust manifolds, etc).

But you raised a good point, something I didn't think of - how dressed engines were at arrival to the assembly line. When did the engine suffix code get stamped on the pad - at the engine plant or added at the assembly line once it was dressed out, etc? By the look of the pics above, they arrived with exhaust manifolds installed, which would lead me to believe the suffix code is stamped at the engine plant before shipping. So they truly did show up at the assembly line as a C or a K-specific engine. I guess... ha. Interesting stuff.

Codes were designated at the engine plant.

K

[jocko]

Thanks Keith!