72 LT-1 Engine, CKY

[John L.]

Hey Guys, I'm looking at a CKY engine; my ID Book says it's a 72 LT-1 W/ MAN/NB2 Trans. What is NB2?
The pad is stamped 1Z3511*** and V1223CKY, I think thats correct it was getting dark. I'm going back tomorrow afternoon. Any additional info would be appreciated. Thanks

[Joe L.]

Re: 72 LT-1 Engine, CKY

Hey Guys, I'm looking at a CKY engine; my ID Book says it's a 72 LT-1 W/ MAN/NB2 Trans. What is NB2?
The pad is stamped 1Z3511*** and V1223CKY, I think thats correct it was getting dark. I'm going back tomorrow afternoon. Any additional info would be appreciated. Thanks

John-----


I've not seen the "CKY" engine code associated with NB-2. However, it's possible that it was. In any event, NB-2 was a production code which deleted federal emissions and replaced it with California emissions. For 1972, though, I don't think there was any difference in the engines as supplied from the engine plant with regard to the ultimate, as-installed emissions configuration of an LT-1-equipped vehicle.

[John L.]

Re: 72 LT-1 Engine, CKY

Thanks Joe,
Would this engine have emmissions? The engine is located in N.C. Says to have around 44,000 miles on it. It's not complete, missing is the heads and intake, carb, dist. Pistons, crank, and cam are still in the block, pan, timing cover and balancer goes with the engine. Was just curious about the other numbers V1223CKY on the pad also.
Thanks for the info.

[Joe L.]

Re: 72 LT-1 Engine, CKY

Thanks Joe,
Would this engine have emmissions? The engine is located in N.C. Says to have around 44,000 miles on it. It's not complete, missing is the heads and intake, carb, dist. Pistons, crank, and cam are still in the block, pan, timing cover and balancer goes with the engine. Was just curious about the other numbers V1223CKY on the pad also.
Thanks for the info.

John-----



ALL LT-1's were originally equipped with AIR. As far as I know, for 1972 they also had the same emissions equipment whether for California or not. I think that "California emissions" for 1972 LT-1 really amounted only to "certification" rather than equipment differences. Anyway, if there was any sort of "real" difference, I don't know what it was.

The "V1223CKY" indicates a 1972 LT-1 engine built in Flint, Michigan on December 23. The block casting number should confirm that the year was 1971.

[John L.]

Re: 72 LT-1 Engine, CKY

Thank You, Joe.

[Terry M.]

Re: 72 LT-1 Engine, CKY

I may be wrong, but I thought for 1972 NB-2 was for the California base engine which not only had a California certification (paper glued to the window), but AIR. Of course that engine would have had a different suffix code. Perhaps there has been a typographical error made in your reference source.

[John L.]

Re: 72 LT-1 Engine, CKY

HI terry,
You are probably correct. I am looking at a project car in the Carolinas, in about 1,000,000 pcs......not really but it sure does look like it. The block is stamped CKY and when I looked it up in one of my books it showed CKY as LT-! W/ Man/NB2. Only CKY was shown this way. There was also CKZ MAN, CRT MAN//AIR, CRS Auto/AIR. I had never heard of NB2 thats why I asked. The book that referenced this is "Catalog of Corvette Numbers 1953-93". Copyright 1993 by AMOS Press Inc.

[Terry M.]

[Joe L.]

Re: 72 LT-1 Engine, CKY

John, Now that the weekend is here curiosity got the better of me and I decided to devote some research time to your question.

In the past I have ranted about the need to go back to original Chevrolet issued documents to establish what happened “back-in-the-day.” This is another of those cases. I’ll spare y'all the rant on that subject. I know it gets old.

I can’t, and won’t try to explain what the publishers of the reference you used had in mind with their posting NB2 with CKY – because it just didn’t happen. I would encourage NCRS members to use NCRS resources for their research. I can’t guarantee the accuracy of NCRS resources, but at least we have the mechanism to get them corrected in those cases where they are inaccurate.

The NCRS 1970-1972 TIM&JG lists CKY as LT1 -- end of story.

NB 2* is listed in Chevrolet documents for all passenger car models for 1972. The two codes listed for Corvette are 350 cid, 200 hp – Codes CDH Manual, and CDJ TH400.
“* Units sold in the State of California must be equipped with RPO NB-2 which consists of the Air Injector Reactor System and a different camshaft which has longer valve overlap (inlet and exhaust valves open simultaneously). This equipment reduces exhaust emissions to insure compliance with California Automotive Exhaust Emission Standards.”

That is what Chevrolet has to say about that matter -- the first NB2 paragraph is my summary of Chevrolet's chart that covers all 1972 passenger car models. The second paragraph – with the asterisk – is an exact quote from Chevrolet's 1972 information.

If you are disappointed in the accuracy of the resource you used I suggest you contact the author or publisher. There are a lot of Corvette references out there. Some are more accurate than others, but none, including the TIM&JG, are completely accurate. We do our best with the NCRS published material, and as I said we have the mechanism to correct ours -- not too many other folks bother to do that.

Terry-----


The strange part is that there was no difference between the camshafts used for 1972 200 hp with or without NB-2. Both used camshaft GM #3896929. So, I think that GM may have released the information you quoted before the "final details" were developed.

There was the difference with respect to exhaust emissions control, though. Engine codes CKW and CKX were for federal emissions (i.e. 49 states) and used CCS and no AIR. Codes CDH and CDJ were for California emissions (i.e. NB-2) and were equipped with AIR. Except for CKW or CKX coded engines, all other 1972 engines were, of course, equipped with AIR.

[Terry M.]

Re: 72 LT-1 Engine, CKY

I didn't look at the date on the subject bulletin, and should have posted it with the quote, it is September 29, 1971. Sometimes these bulletins are re-released later in the model year, but that is not the case in 1972.

I do have some Flint build documents for 1972. As I get the time I'll look to see what they were supposed to install for a cam in those engines. I haven't paid too much attention to the internal engine data since it is not subject to judging. I would guess the number of people interested in the camshaft installed in those NB2 engines will be limited to just a few of us.

FWIW: Those of us out here in the hither lands don't get to see these engines too often. Years ago one of my friends went to California on the chance of purchasing one. It had a paper label glued low on the windshield listing the California emissions certification and the PPM of HC & CO. He sent me pictures of the car, with some details, but this was in the good-old pre-digital days. Someplace I have those photos. Living where you do, you likely have more opportunity to see these uncommon Corvettes than I do.

Edit add:
Well Joe, you really got me digging into the musty old files.

The 1972 Camshaft Assembly sheet from Flint is dated 9-9-71
CKW & CKX got camshaft assembly 3896929 Identified as plain
CDH & CDJ got camshaft assembly 3998962 Identified as blue band
And just to round it out, while I have this stuff out:
CKY got camshaft assembly 3972178 Identified as pink band.

Maybe the LT1 cam was pink to match the pink rods. Color coordinated internals must have made the workplace a little less grim.

I’m not sure how much this helps or hurts as these are production numbers, and may never have been available as SERVICE parts. It is however what the 1972 Flint build sheets call for. Perhaps they decided to service only the 3896929 part.

13 different passenger car engine codes got the 3998962 camshaft assembly, and 12 truck engine codes are listed for it.

[Joe L.]

Re: 72 LT-1 Engine, CKY


Terry-----


That's good information. Camshaft GM #3998962 definitely did at one time exist. However, while it was once cataloged for many 1972 Chevrolet small block applications with NB-2, it was never cataloged by GM for a Corvette application. Of course, that does not mean that it was not used for a Corvette application. It carried casting number 6262944. It was discontinued from SERVICE in February, 1986 and replaced by GM #340284, which was a part number that actually dated back to 1973. It is now discontinued, though.

The specs on the GM #3896929 and 3998962 are shown below. The 3896929 is shown on the left and the 3998962 on the right:


intake lift--------------------0.390-----0.401

exhaust lift------------------0.410------0.410

intake duration (degrees)------310-------320

exhaust duration (degrees)----320-------334

[John L.]

Re: 72 LT-1 Engine, CKY

Terry...Joe,
What a wealth of information from you two.
Since my CKY engine is cam less right now I will be installing a new 3896929 or current number for the LT-1 engine.
Terry I do trust my NCRS reference nanuals, I do have the current version of 70-72, I knew CKY was a LT-1, I just didn't know what NB2 was. Interesting how a CKY engine destined for California has been here in the Carolinas since 1975. This engine has been setting since 75, it's said to have less than 40,000 miles on it. Biggest problem is it has been dissasembled since 75, It's missing the cam, Heads, Intake & Carb.
But I now have my LT-1 to work on. It makes a good companion to my LS-5. Take care...Thanks for all the good Info.

[Joe L.]

Re: 72 LT-1 Engine, CKY

Terry...Joe,
What a wealth of information from you two.
Since my CKY engine is cam less right now I will be installing a new 3896929 or current number for the LT-1 engine.
Terry I do trust my NCRS reference nanuals, I do have the current version of 70-72, I knew CKY was a LT-1, I just didn't know what NB2 was. Interesting how a CKY engine destined for California has been here in the Carolinas since 1975. This engine has been setting since 75, it's said to have less than 40,000 miles on it. Biggest problem is it has been dissasembled since 75, It's missing the cam, Heads, Intake & Carb.
But I now have my LT-1 to work on. It makes a good companion to my LS-5. Take care...Thanks for all the good Info.

John------


I think we've got more than 1 subject going on here. The NB-2 issue is really only applicable to the base engine for 1972, NOT the LT-1. IF NB-2 was applied to any LT-1's for 1972, as I mentioned previously, it was only a "certification" issue. There was no difference in engine components or peripherals for LT-1.

I believe that CKY was the identification code for most 1972 LT-1's and was NOT limited to California-delivered cars. I really don't think there was any difference in the suffix code for 1972 with LT-1 regardless of where it was delivered. I believe, and I think this was Terry's point too, that NB-2 had no relevance for 1972 LT-1's.

I believe that 1972 LT-1's which were also equipped with C-60 (1972 was the only year that C-60 was available with LT-1), used engine suffix code CRT.

So, you DEFINITELY don't want to use the equivalent of the GM #3896929 camshaft for an LT-1. You want to use camshaft GM #3972178 which is discontinued. However, it's available as a Crane-manufactured camshaft and lifter kit under GM #12364054.

[Terry M.]

Re: 72 LT-1 Engine, CKY

John,
I am sorry Joe and I took this thread away from your original question, but we both had too much fun to pass up on the opportunity to dig deep into the musty recesses. Although in fairness we got your question answered before we got off on the NB2 subject. You are right in that the TIM&JG is less than clear about the option. We could have done that one better.

BTW: There is no indication in anything you have told us about the CKY components that ties them to California. On the contrary there are those who believe the 1972 LT1 was not available for sale in California because it did not meet the emission standards that brought about the NB2 for the base motor. We have documentation that the LS5 was not for sale in California in 1972, but the same material is silent on the LT1.

Interesting putting all this back together nearly forty years later. Thanks for giving us a chance to have some fun.

[Louie C.]

Re: 72 LT-1 Engine, CKY

The CKY engine I had, upon disassembling, was a base engine. It was listed in the GM parts catalog of the time(Sep 71) as an LT1. Just know that the undisturbed engine I tore down in mid 70's was a base engine