C3 1970 LT-1 Emissins

[William J. #42757]

My first try here.
We have a very early,Jan. production LT-1 and it was a dealer ordered Calif. car it has the heat shield plate below carb but what else was only for California delivery? The film attached to the Lh front firewall-hood latch area is the white 1.5"X6" size but it is not in great readable condition yet appears as correct & original. Just below that area is a slight buffed area that appears as a location for another film, but what? What is NB2?

[Geoff C.]

NB2 is show in the back of the AIM *NM*

[Joe L.]

Re: C3 1970 LT-1 Emissins

William-----

As far as 1970 LT-1 with California emissions, the only difference between California and non-California related to the carburetor, heat shield/carb gasket that you noted, and the installation of the NA-9 fuel vapor control system. As part of the NA-9 system, the fuel tank had a nipple fitting and fuel seperator mounted on the driver side of the tank.

NB-2 is, basically, an internal option code which deleted federal emission and "over-rode" that requirement with the California spec systems(s). I don't know, for sure, if it was used as early as 1970, though. As far as I know, it was first used for the 1972 model year but, it's possible that it was used earlier. No earlier than 1970, though.

[Tom R.]

Re: C3 1970 LT-1 Emissins

William:

The other film (your NB2 reference) is probably the early version of the California emission certification...I may have seen one among early C3s but don't recall. May have a photo of it somewhere but also have a repo that shows the CB broadcast code and GM #3989361 included when NA9 was installed. This is reference in the 70-72 tech manual on page 71.

But in later years, specifically 73, NB2 was lashed up with RPO YF5 when California emissions was called out. NB2 was the hardware configuration while YF5 was the test and certification for CA emissions. I've seen this pattern on 73, 78 and 82 C3 build sheets.

It also had the sealed gas cap to accompany the evaporative control system (cannister and fuel tank separator). I would like to see some photos if you can post or send...hope this helps.

[Robert E.]

Re: C3 1970 LT-1 Emissins

Tom,

I have a very late built '71 LT-1 #21701 of 21801. I have been puzzled by a yellow CB emmisions sticker (#3983361) located below the AX coded tuneup chart. The '70-'72 TIM/JG on page 71 lists a CB label for 1970 and early 1971 with a 3989361 label. Does this sticker mean that my car was a California delivered car? Whats with the different part numbers on the CB stickers?

I have posted a couple of images at:

http://tinypic.com/1roj0o

http://tinypic.com/1roj8h

Thanks

Robert

[Tom R.]

Re: C3 1970 LT-1 Emissins

Robert...all 71s were equipped with NA9 or ECS...this was the first year all Corvettes were equipped with evaporative control system.

The CB broadcast code indicates that the car is equipped with evaporation control system to capture fuel vapors and how to tune when vehicle is equipped with ECS.

Some nice pics there as well. The 3994020 part was used in 1971 for the LT1 motor with K66 transistor ignition and the top left corner shows an X which as you indicate corresponds to the AX broadcast code. So do you have TI and what's your engine suffix code?

[Robert E.]

Re: C3 1970 LT-1 Emissins

Tom,

Thanks for the info. Yes, my car is equipped with TI, and has a matching numbers CGZ suffix code. Do you have any explaination with regards to the different part number on my CB decal compared to the one listed in the JG?

Robert

[William J. #42757]

Re: C3 1970 LT-1 Emissins

Thanks Tom,
If I can figure out the basic concept to send the pictures I will ASAP, trying to understand my error.
I believe mine would be the CL that you mentioned on pg. 71 because on my very low # everything else is there and appears correct, what is GM#3989361? The film is tuff to read as age has taken it's toll, would be happy to send.

[Tom R.]

Re: C3 1970 LT-1 Emissins

The short answer is...its never been corrected and may be a typo. I'm being sarcastic and only suspect its in error. Perhaps the LT1 gurus will jump in and shed some light on your question.

[Terry M.]

Re: C3 1970 LT-1 Emissins

Tom and Robert,
The CB emissions label has nothing to do with LT1, or at least it has no more to do with LT1 than with the base motor or LS5 or LS6. It related to what in 1970 was the NA9 vapor emissions control system. That system, which was optional in 1970, became standard with 1971 production. In 1970 those Corvettes equipped with NA9 received the CB label as a means of identifying them as being equipped with the NA9 option. Early 1971 Corvettes (the first 2000 or so) received those labels as a means of identifying them as having what was then a new emissions system. By the end of 1971 production one might expect technicians to be familiar with the system and the need for a label would be diminished. We do not usually see this label on 1971 Corvettes beyond those early models mentioned.

[Robert C.]

Re: Tag Part # *NM*