1972 NB2 emissions control

[Bob H.]

I just purchased a nice unrestored 72 convertible with optional hardtop. Other than some nicks and chips, the paint is original as well as the interior and most of the engine compartment. An extra surprise was the never down Firestone Wide Oval spare. It was a California car and has NB2 in the suffix. What does NB2 actually consist of? The air pump etc was removed years ago but I have all the parts but don't see anything extra.

[Joe L.]

Re: 1972 NB2 emissions control

I just purchased a nice unrestored 72 convertible with optional hardtop. Other than some nicks and chips, the paint is original as well as the interior and most of the engine compartment. An extra surprise was the never down Firestone Wide Oval spare. It was a California car and has NB2 in the suffix. What does NB2 actually consist of? The air pump etc was removed years ago but I have all the parts but don't see anything extra.

Bob------


I'm assuming this car is an L-48. RPO NB-2 denoted waiver of federal emissions and installation of California emissions (which also complied with federal emissions). As far as I know, for 1972 the only equipment change involved the installation of AIR for L-48. I don't know of any other NB-2-specific components that were installed for that year. However, the emissions label should be "LK" coded

[Mark E.]

Re: 1972 NB2 emissions control

For 1970, CA emissions added EEC. But sometime between 1971-1973, all cars came equipped with EEC.

It sounds like Joe believes it EEC was standard by 1972.

[Joe L.]

Re: 1972 NB2 emissions control

For 1970, CA emissions added EEC. But sometime between 1971-1973, all cars came equipped with EEC.

It sounds like Joe believes it EEC was standard by 1972.

Mark-----


EEC became standard for all Corvettes beginning in 1971.

[Mark E.]

Re: 1972 NB2 emissions control

Thanks Joe.

[John C.]

Re: 1972 NB2 emissions control

Bob

GM specs for 1972 list the addition of the AIR system, changed timing specs, and a different cam with a revised lift and duration as the only difference between the base engine and the base engine with CA equipped emissions.

John

[Joe L.]

Re: 1972 NB2 emissions control

Bob

GM specs for 1972 list the addition of the AIR system, changed timing specs, and a different cam with a revised lift and duration as the only difference between the base engine and the base engine with CA equipped emissions.

John

John------

Even if these camshaft specs originate from a GM source, I think they're inaccurate. I know of no unique, specific camshaft for 1972 L-48 applications with California Emissions. This could be one of those things that was planned but never actually put into PRODUCTION and, somehow, the specs got "out there"..

[John C.]

Re: 1972 NB2 emissions control

Joe

The source is the published specs from the GM heritage center. What actually got produced I have no knowledge to verify one way or the other.

Bob, if the engine hasn't already been rebuilt, and you have a need to do it in the future, try to have the cam measured. Who knows, we may all be surprised.

John

[Mark E.]

Re: 1972 NB2 emissions control

This is the first I've heard that California has different cams.

According to the Corvette Parts Catalog dated 1978, the 3896929 cam was used from 67-79 (and maybe later given the date of the catalog) for 327, 350 "exc h/per, sp h/per". This is the L75/L48 standard engine for these years. There's no other cam listed for the standard engine.

I'm sure Joe can share more details.

[Joe L.]

Re: 1972 NB2 emissions control

This is the first I've heard that California has different cams.

According to the Corvette Parts Catalog dated 1978, the 3896929 cam was used from 67-79 (and maybe later given the date of the catalog) for 327, 350 "exc h/per, sp h/per". This is the L75/L48 standard engine for these years. There's no other cam listed for the standard engine.

I'm sure Joe can share more details.

Mark------


There was a cam released in about 1980 which replaced the long-serving GM #3896929. This cam, GM #14060651, had very slightly different specs than the 3896929 for emission-control purposes. However, in 1972, this cam was a long way from existence. The 14060651 is still available from GM for all applications originally using the 3896929.

[Bob H.]

Re: 1972 NB2 emissions control

r the response. It has not been rebuilt so I will be able to check when the time comes.