Question? 1970 EEC

[Stephen B.]

I don't understand what the Chevrolet parts book means by EEC. Is that the same as AIR pump system or the California only ECS system?

[Joe C.]

Re: Question? 1970 EEC

Stephen,

EEC = "Evaporative Emissions Control"

Joe

[Stephen B.]

Re: Question? 1970 EEC

That's correct and thank you, but what cars had the system? Is my 1970 LT-1 with a smog pump and no return line from the carb to the tank an EEC car? Is my 70 350/350 with a PVC valve and a second fuel line that runs back to the tank an EEC car?

[Joe C.]

Re: Question? 1970 EEC

Stephen,

Take a look at this website:

http://www.corvetteforum.net/c3/1970registry/codes.html

My feeling is that California cars required NA9 in 1970, and then EEC/ECS was mandatory nationwide in 1971.
Your L48 may have been a California car.
Your LT1 may have been a "49 State" car.
The 350/350 with the return line sounds like a EEC car (California) to me.

Joe

[Dick W.]

Re: Question? 1970 EEC

Bunkster, look in the left inner fender at the cowl. If your car had EEC there should be a cannister about the size of a one pound coffee can. This is the eveporative emissions cannister.

[Stephen B.]

Re: Question? 1970 EEC

Thanks Joe for the link. All Quadrajet (300,350, 390 HP) cars had a return line from the fuel pump to the gas tank. Only the Holley equipped LT-1 did not have the return line. I get the feeling that all Quadrajet cars had EEC for all 50 states. ECS was California only. The carb had a carbon canister attached by a hose. I believe that only the 350/350 did not have an AIR pump in 1970. It did have the AIR pump in 1969 though. I just want to make sure that when I start looking for a gas tank for my LT-1, I'm getting the right tank. The 53-72 parts manual shows both an EEC 350 Special High Performance and a non-EEC Special High Performance. Special High Performance meaning LT-1 350 in 1970. Sometimes the parts books get confusing. Thanks again for your input.

[Stephen B.]

Re: Question? 1970 EEC

It that the carbon cannister? I want to make sure that I'm looking for the correct fuel tank for my LT-1 car. I don't believe that LT-1's in 1970 had the cannister. I received the car in pieces and not sure if a cannister is suppose to be there.

I missed you at the Judges Retreat.

Thanks,

Bunky

[Dick W.]

Re: Question? 1970 EEC

Bunky, look for evidence of an additional decal near the emissions label. The NA9 cars had a yellow label. Also look for additional vacuum hoses in the area of the charcoal cannister. Chances are your car did not have it but stranger things have happened. There is a ZR-1 '70 that was supposedly sold new in the mid west that has the NA9 system.. Go figure

[Kenneth B.]

Re: Question? 1970 EEC

I beleave NO 1970 LT-1 cars had the EEC can with return line & all the rest had them in all states.

KEN 7808

[Dick W.]

Re: Question? 1970 EEC

Ken I believe that the EEC cars had a line on the LH side of the frame. The quadrajet equipped cars had the return line on the RH side of the frame.

[Stephen B.]

Re: Question? 1970 EEC

Thanks Ken. So how did the EEC work? A cannister connected to the gas tank? Was it also connected to the carb?

[Terry M.]

Re: Question? 1970 EEC

There is an explanation of the NA9/EEC system in the May 1970 Chevrolet Service News (CSN), which should be a supplement to the 1970 Chassis Service Manual. If you own a 1970 Corvette and don't have that issue of CSN, get a photo copy from the membership office of this organization. There is also an explanation of the EEC system in the 1971 Chassis Service Manual -- it was standard on ALL 1971s, and in neither year does it have anything to do with the passenger side fuel return line.

In 1970 NA9 was required for Corvettes (and some other GM vehicles) delivered in California, but nothing prohibited its inclusion on vehicles delivered in the other states. Sadly people have come to refer to it as a "California option," and that has created the false impression that ALL Corvettes with NA9 were delivered to California -- NOT so. In 1970 NA9 was available on ANY Corvette engine for a car delivered ANYWHERE.

[Joe L.]

Re: Question? 1970 EEC

Bunky-----

The fuel return line was, as you described, used for 1970 Corvette applications with Rochester Q-Jet. This line was on the RIGHT (PASSENGER) side of the car. LT-1 1970 Corvettes had no fuel return line on the RIGHT (PASSENGER) side of the car.

1970 Corvettes equipped with NA-9 (evaporative emissions control or EEC) which was required for operation in California but MAY have been available anywhere if someone wanted to order it, used a return line on the LEFT (DRIVER) side. ALL 1970 Corvettes equipped with NA-9 had this LEFT side line regardless of whether or not they also had the right side line. The left side return line returned fuel to the fuel tank from the evaporative emissions control system.

For the 1971 model year, ALL Corvettes got the EEC system as COMPONENT OF of the "combined emissions control system" or "CEC".

[Jack H.]

Re: Question? 1970 EEC

On NA9, Calif Emissions cars, there was a liquid separator in the gas tank that fed fumes from the LH upper side of the tank, forward along the LH frame rail to the charcoal cannister in the engine compartment. The bottom of the cannister had a cloth filter allowing outside makeup air to enter the cannister and flow through the charcoal that would trap/hold raw gasoline fumes on engine shut down.

The top side of the cannister connected to the carb via rubber hoses and a check valve. On engine start-up, unburned/trapped gasoline fumes were pulled from the storage cannister to/through the carb for combustion.

While California amounted to roughly 10% of Chevy's 1970 Corvette production volume, we RARELY see NA9 equipped cars on the judging field. Why? Well, probably because the prior owner chain stripped out and discarded the NA9 unique parts....

You might want to study your copy of the 1970 AIM book under the NA9 option to see the individual PN differences used on these cars vs. their 49-State counterparts. As already mentioned, the EEC system used on '70 Cal cars would become standard production for 1971 when the new 50-State Federal emissions standards went into effect.

No only did lawmakers target tailpipe emissions (NoX, HC, Etc.), but they were addressing raw gasoline vapor emissions generated by evaporation from both the fuel tank as well as the carb's fuel bowls and this is what the EEC system was designed to address....

[Joe L.]

Re: Question? 1970 EEC

Terry-----

The system had value for a car delivered anywhere if the purchaser was savvy enough to figure it out. It helps reduce the "gasoline fumes in the garage" syndrome which is common for cars not equipped with EEC.