California emissions 1970

[Tim G.]

Re: California emissions 1970

Joe, it's interesting that the NA-9 option was only available for cars delivered to California. It must have been inconvenient for them to option out a car delivered this way. I know that the K19 option in 1966 and 1967 came through on a few cars not ordered for California.

I have to ask, what in the world did the heat shield do to improve emissions?

[Joe L.]

Re: California emissions 1970

Joe, it's interesting that the NA-9 option was only available for cars delivered to California. It must have been inconvenient for them to option out a car delivered this way. I know that the K19 option in 1966 and 1967 came through on a few cars not ordered for California.

I have to ask, what in the world did the heat shield do to improve emissions?

Tim------


Even for 1966-67 GM specified that the K-19 option was "exclusive to California vehicle registrations only". I suppose it's possible that there were exceptions but I'd only believe it with irrefutable documentation.

For 1970, most of the carburetor-related elements of NA-9, with the exception of calibration, were intended to reduce evaporative emissions. This included the heat shield.

[Tim G.]

Re: California emissions 1970

Joe, I know of only two documented K19 non-California optioned cars. Oddly enough, one is a Canadian car with Canadian paperwork.

[Mark E.]

Re: California emissions 1970

I have to ask, what in the world did the heat shield do to improve emissions?

Retarded timing and leaner fuel mixture makes an engine run hotter. The shield is added to help reduce percolation.

[Terry M.]

Re: California emissions 1970

Joe, it's interesting that the NA-9 option was only available for cars delivered to California. It must have been inconvenient for them to option out a car delivered this way. I know that the K19 option in 1966 and 1967 came through on a few cars not ordered for California.

I have to ask, what in the world did the heat shield do to improve emissions?

Actually Tim it is a little different for 1970. The NA9 option was mandatory for California delivery, but it was available for order regardless of where the car was delivered. I have heard claims of California delivery without NA9, But close scrutiny has proved questionable.

[Robert C.]

Re: California emissions 1970

Mark, What would I look for on the fuel tank to see if the emmisions have been properly bypassed as the cannister and carb have?

[Joe L.]

Re: California emissions 1970

Mark, What would I look for on the fuel tank to see if the emmisions have been properly bypassed as the cannister and carb have?

Robert------


Fuel tanks for 1970 with NA-9 have a nipple with attached plastic "separator" on the upper LEFT side of the tank. This is where the return from the vapor canister is directed. If your car has the vapor canister eliminated, then this is already non-functional. You could remove the return line and separator and plug the nipple if you so desire but I don't think it's absolutely necessary.

Just to be clear, you cannot remove the fuel return line on the upper RIGHT side of the tank.

[Mark E.]

Re: California emissions 1970

Mark, What would I look for on the fuel tank to see if the emmisions have been properly bypassed as the cannister and carb have?

Joe already answered this. I wonder if the gas cap/tank vent is different too?

If the vapor return line that runs the length of the car is intact, consider reactivating the EEC system. Since the canister is there, this would mostly consist of installing vapor hose and clamps.

Later, you can also find and install an NA9 compatible airhorn (or get the correct Quadrajet) that features a sealed bowl vent.

Three benefits: the car will stink up the garage much less, evaporative emissions will decrease significantly, and the value of the car increases. There's no performance penalty for EEC so it's a mystery why it was bypassed in the first place.

Capturing and burning evaporative emissions is one of the most effective smog controls invented, and yet it does not impact performance.

[Joe L.]

Re: California emissions 1970

Joe already answered this. I wonder if the gas cap/tank vent is different too?

If the vapor return line that runs the length of the car is intact, consider reactivating the EEC system. Since the canister is there, this would mostly consist of installing vapor hose and clamps.

Later, you can also find and install an NA9 compatible airhorn (or get the correct Quadrajet) that features a sealed bowl vent.

Three benefits: the car will stink up the garage much less, evaporative emissions will decrease significantly, and the value of the car increases. There's no performance penalty for EEC so it's a mystery why it was bypassed in the first place.

Capturing and burning evaporative emissions is one of the most effective smog controls invented, and yet it does not impact performance.

Mark------


The fuel cap is the same for non-NA-9 and those with NA-9. It's a "sealed" cap. All 1970+ used a "sealed" fuel cap. Very late 1969 could also use a "sealed" cap but originally did not.

You are correct that the NA-9 system caused no performance disadvantages. The CCS (controlled combustion system) system did result in performance problems. All 1970's were so equipped except LT-1.

[Robert C.]

Re: California emissions 1970

Thanks for the info. The cannister is plugged in two places but the return line going to the tank is still connected. When I pull the spare tire carrier to change the rear end grease, I will check out the tank area.

[Robert C.]

Re: California emissions 1970

Thanks Mark. The return line from the cannister is still connected but other two are plugged. I will check at the tank and see what's going on there. I probably will get a correct carb in the future. I am the third owner and I purchased the car in South Carolina. Not sure when the car got to the east coast but apparently one of them disconnected it and messed with the carb. Don't know the first owner and the second owner ended up with dementia so information is lost. The car was delivered to Lamb Chevrolet, National City, CA originally.

[Mark E.]

Re: California emissions 1970

Mark------


The fuel cap is the same for non-NA-9 and those with NA-9. It's a "sealed" cap. All 1970+ used a "sealed" fuel cap. Very late 1969 could also use a "sealed" cap but originally did not.

You are correct that the NA-9 system caused no performance disadvantages. The CCS (controlled combustion system) system did result in performance problems. All 1970's were so equipped except LT-1.

According to the owners manual, CCS consists of thermostatically controlled intake air, high temperature thermostat, changed spark timing, and leaner carb setup. Corvette has all of those except the heated air intake.

1970 also features Transmission Controlled Spark (TCS) which locks out vacuum advance except in high gear and reverse. This is missing on the OP's car, but his VAC is attached to ported vacuum which has a somewhat similar effect on timing.