Going through my corvette by the numbers book. My block pad has a partial VIN, then V0108CTU. I know what all this is. When it comes to the CTU it's vague on what this actually means. I realize it's the earliest version of the LT-1. The C says motor division which would be chevy. I can't find or I'm missing what the T and U or the TU together mean. Also the block date stamp is J239. I know the J is the month of Oct, pretty sure 23 is the day of the month and then 9 would be 1969.

 

CTU is the complete suffix code. The single letters doesn't break down to signify anything

 

I read too much into the C by itself. I knew what the CTU as a code meant.

 

You have somewhat of an anomaly with the casting date and the assembly date. October 23 to January 8 is a pretty long time to have a bare block sitting around Flint. There was a strike that extended the '69 model year well into the standard 1970 model year so that may have played a role. Something to look into is whether other cars built around mid-January also have an October/November block.

The '70 Corvettes used a series of codes all beginning with CT: D, G, H, J, K, L, M, N, O, P, Q, R, U, & V. The CT has no meaning as it was used across various other Chevrolet models in '72, '74, '75, '76, '78.

 

If your pad is stamped "0108" (which would be January 8th), and your block is cast "J239" (which decodes as October 23, 69), then something seems out of line.

"J239" is the date the block was cast at Flint (October 23rd, 69), while "0108" is the date the engine was assembled by Flint (January 8th, presumably 1970). I'm not saying that it's not possible that a block cast October 23rd wasn't assembled into a complete engine until January 8th, inventory control wasn't what it is today, but two and a half months is definitely not typical. Normally an engine was assembled within a couple days of when the block was cast. I'd be curious to know what the casting dates of some of the other components of the engine, like the heads and intake manifold were.

There was a major strike in 69 that delayed the introduction of the 70 Corvette and Camaro, but that took place in May. Around 4900 Corvettes were built between October and December 69, so it's hard to believe that a May strike effected the assembly of blocks cast in October?

In 1970 Chevrolet started using three digit suffix codes in place of the two digit codes previously used. Just like when they went from a single digit suffix code to a two digit code in the late 50's, by 1970 they likely needed to add the third letter to identify the ever expanding variations of available engine options. While codes starting with "C" were common in 1970, over the years Chevrolet used three digit codes starting with "A", "B", "C" "D", "F", "O", and others letters, with the first letter having no more significance than the first letter in the previously used two digit codes. I believe it was just a letter picked to be part of the suffix code.

Oh heck, it looks like 67:72 responded quicker than me with a similar answer...and questions.

 

I sure hope somebody didn't fake this in such a way that it wouldn't hold up to scrutiny later. The winters intake is a high rise with the correct number but haven't found a date code yet. The heads have a K25x the last can't read. The water pump is K259 no longer installed but I have it. The alternator 9K17, the air pump is dec 1969, the carb 3972121 list 4555 dated 9B2. The carb is not on the car but rebuilt in a box. The receipts i have tells an interesting story why it's not on.

 

Can you post a clear picture of the stamp pad that had no paint on it. And if it does have paint only use a chemical to remove the paint.

 

 

You guys really get " down in the weeds " with this stuff. I'm impressed, more power to ya!

 

That pad has been altered or touched. The milling cutting lines are going the wrong way for a flint block

 

I think the casting date for at least some aluminum intakes is on the bottom side. Never had one, so never put the trivia to memory.

 

Looking at the surface of the stamp pad I can't quite decide if the pad was cleaned with something abrasive like sand paper, or if it has been decked and restamped? The stamping itself looks typical of factory stampings, but the pad surface is an issue.

Correct, the Winters aluminum manifolds normally have the casting date on the underside, and usually hidden by the manifold's splash pan. Cast iron intakes have the normally have the date cast into the top of the manifold.

 

October 23 to January 6 is certainly longer than is typical for one of these engines, but it is not out of the realm of possibility. Taking everything into account (casting date, assembly date, VIN derivative) gives us a much better picture.

This is a comparative pad close to the assembly date of the OPs engine.



First 0, 1, and C are all different… That doesn’t address the VIN derivative in the OPs photo (which we can’t see). Add that to the long spread between casting date and assembly date… Would be nice to see the VIN derivative.

Regards,

Stan Falenski