Early '70 Gas Cap Question

[Carr C.]

My '70 LS5 Convertible appears to be very original. I have disected it several times with the judging guide, and I find more and more things I look at are correct and date coded properly. There really isn't anything other than the alternator, the master cylinder, and the fan clutch that wasn't correct when I bought it.

The car has all documentation including the tank sticker, order copy from under the dash, window sticker, and a bunch of other documents that have been very well kept over time, and around 80,000 miles on it.

The car has a '69 style "VENTED" gas cap with the serated looking edge. I was curious if this could possibly be the original cas cap because the car was built so early in the the '70 production year? The car was built on B19, and was # 4,242 down the line.

The JG says I should have the same looking cap, but it should read "SEALED" on it, which apperas to be a one year only cap, because the JG says there is an additional Open Slowly emblem on the '71's.

What is the opinion on this?

Thank you,

Carr

PS> I enjoyed meeting everyone at the Nationals!

[Chuck S.]

Re: Early '70 Gas Cap Question

In my opinion, it's very unlikely it came from the factory that way.

Gas caps are the thing that many drivers leave on top of the pump, then drive away and leave. The new owner probably lost the original cap before he was even accustomed to his new car, and picked up a new one at the dealer. Unfortunately, the only one the dealer had in stock was incorrect...I believe changes to force vapors through the canister only started in 70 with the sealed systems.

On the driver side door, there should be a blue sticker that certifies the car met all Federal requirements for 1970 MY. The Feds would be very interested in EPA requirements being met; GM would not let a car out the door that did not meet the emission requirements...big fines would follow. Another thing to confirm this would be the presence of the charcoal canister under the hood...if the canister is/was on the car, then the gas cap would have been the proper type.

[Dennis D.]

Re: Early '70 Gas Cap Question

Agree with Chuck. But, the canister,(EEC system), was a calif thing in 70. My 70 L-46 isn't a calif, no canister, sealed gas cap.

[Chuck S.]

Re: Early '70 Gas Cap Question

Yeah, my base engine doesn't have it either...I guess it was only on the LS5 and LT1, and only in California.

Anyway, if the Feds had certified the car with a sealed fuel system, it had better have a SEALED fuel system. Forget about trying to use any $2 gas caps left over from 69...they would have sent them to service parts.

[Mark #44888]

Re: Early '70 Gas Cap Question

Hey, we're almost related: Mine was a B19 also, #4269. I've got an L46 coupe. I recently had an issue with a non-vented cap, that has me using a vented cap: Replaced tank with a correct tank for my car (non-cal, no canniseter). About a month after I started driving it, I noticed the gas tank filler opening had "dropped" down about 2 inches from where it was the day before. Turns out, the tank collapsed inward due to not having any ambient venting. I replaced the tank, along with a vented cap, and no problem to date. Still don't know "why" this happened; no one else could tell me either.

[Chuck S.]

Re: Early '70 Gas Cap Question

After August 69, Corvette fuel tanks had a vent valve built into the top of the tank, which allowed the use of the "SEALED" gas cap. Someone must have sold you an unvented tank in error...or, the tank's vent valve was faulty.

Your tank should be this one: http://www.quantaproducts.com/prodin...?number=GM-33E