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2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
68 69 where the only C3s with the vented cap...but if your evap system is clogged the vented cap will get you by until you can get the charcoal system cleaned/replaced. It wont hurt anything except for a few Liberals rear ends. The charcoal system just got rid of the gas smell, nothing more. Same as the early A.I.R. system. It just added air to the exhaust to dilute it to get the numbers down....
To sum it all up, unless it is a California car with a functioning evap system you dont NEED a sealed cap but it came with one.
The benefit of having a vented cap is that if something should happen to the tanks vent system you have a secondary vent and will not experience a collapsed tank.
In 1970 the NA9 Evap System was only installed on California delivered cars. But all 1970 corvettes were equipped with a sealed cap.
I found a reference which implied that the 1970 NA9 system used a different gas cap. I have been unable to find any other info. Any one with a 1970 California vette that has a known original cap? If so, please post a picture.
I found a reference which implied that the 1970 NA9 system used a different gas cap. I have been unable to find any other info. Any one with a 1970 California vette that has a known original cap? If so, please post a picture.
My 70 California BB has a sealed ventilation system. It appears the only way air can get into the fuel tank is via the charcoal canister in the front of the car. Seems to me this is a restriction on air entering the system as fuel bleeds down through depletion. I'd replaced that sealed tank cap with "normal" pre-SMOG cap. I just ordered a sealed cap and it's on back order. I'd like to have sealed cap handy to avoid registration hassles.
My 70 California BB has a sealed ventilation system. It appears the only way air can get into the fuel tank is via the charcoal canister in the front of the car. Seems to me this is a restriction on air entering the system as fuel bleeds down through depletion. I'd replaced that sealed tank cap with "normal" pre-SMOG cap. I just ordered a sealed cap and it's on back order. I'd like to have sealed cap handy to avoid registration hassles.
I echo Boat196’s. question. What is your concern regarding CA registration? CA does not require 1975 and older vehicles to undergo smog checks for valid registration. Feel free to use whatever cap you have handy and works for you. 👍🏻
Here are some original and service gas caps used from 1970 till 1974. Original GM the twist tab points away from the word SEALED until the caution info was stamped into the cap and the spot welds are small in comparison the later service and reproductions. The SMC (Stant Manufacturing Corporation) Logo changed to just an "S".
1970 sealed
From post earlier
Original SMC logo would be on all original caps 1970 till 1974
Later service and Reproduction Logo
early 1971 till late in production with Caution Plate
Reproduction Caution plate
Later 1971 and 1972 Production
Maybe on later 1972 production till 1974 as 1975 used smaller cap as unleaded fuel with Catalytic Converter
On original caps used when leaded fuels were used a white coating would be on the bottom caused by the Tetraethyl lead fuel.
Large and small spot welds
Also notice the difference in the word stamping from an original and later reproductions
