strange.
I have the same thing and when I park the car in October and start it the last of april my gauge still shows full. my ss cap is loose and if I launch hard with a full tank I can see where it splashed a little on the bumper
this is in a heated garage

 

No Ethanol in CA? Really?

 

Fuel evaporation is caused by cycling between high and low temperatures. I would not expect to see much loss in a heated garage with a more or less constant temperature. If you go with a non vented cap make sure the tank is full or you could actually deform the tank or cause a leak. I wouldn’t do it....

Don

 

No Ethanol in CA? Really?

Car is in upstate NY now, hence the winter storage. Ethanol free is more expensive but I use it in the old car and small engines.

 

hence the winter storage

Yep missed that. Its about time for our two days of winter here in TX.

 

Aren't standard fuel tank caps vented to allow air in, but not out? I've experienced fuel being pushed out of a disconnected fuel line at the carb (while I was working on the carb off the car) due to the tank heating up in the sunlight with the cap on, but not the opposite. When I removed the cap the fuel stopped dripping from the line at the carb. Air is allowed in as fuel is removed, but not the opposite. Can't see how you're losing that much fuel when the car sits for a long period unless your fuel tank cap is defective and lets vapors out.

 

It's the original cap, so after 50 years maybe it doesn't seal at all, in or out.

 

Could it just be your memory is slightly failing with regards to how much gas was really in it when it was stored? :wink2: or maybe you burned up more than you realized between filling it up and driving it to your storage spot. Or the float & sending unit itself could be slowly failing.

I will see evaporation with my car in storage, though I never paid complete attention as to how much for the whole or even half-a-winter.

 

Could be bad memory Bob!

I have not hardly put gas in all year because the gas was old from last winters storage (with Stabil) and I wanted to cycle it out. Last drove it in September and thought it had about 1/4 tank on the gauge, but that's 50 years old so may be flakey as well. Sometimes the gauge takes a while after starting to read and it stayed on E when I started it. So low I put some spare fuel in the trunk in case I didn't make it to the station. It took 16.3 gallons which is about the most I have ever put in.

We did have a lot of temp fluctuations over the last 4 Fall months, so maybe that had something to do with it.

It also evaporates all the fuel from the carb bowls after about 3 weeks, so I usually fill those through the vent tube before firing it up to prevent extended cranking.

I guess I will find out in about April when I take it out again.

 

I keep a strict gas mileage log in my 67 and it usually gets 12-13 mpg local and 18-20 highway. That being said I have noticed that from when I park it in December to when I start driving it again in April the mileage will drop to 8-9 mpg. then pop back up to 12-13 after the first fill up. Always wondered if the fuel evaporated.
I have a locking Bowtie cap that never seams to sit on the filler neck right, think I'll switch to a plain twist-on cap. Anyone have one for sale in Tuxedo Black?

 

I live in Orlando, Florida, and recently I lost what I thought was a good 1/4 tank of fuel when I went to crank the engine this past week. I too seem to get evaporation with the car just sitting in the garage. I finally got tired of having to crank the engine for a good 15 seconds to get fuel from the tank and fill the bowl(s) of the carb to get it to fire up. I installed an electric pump by the fuel tank, and removed the mechanical fuel pump on the engine block.

I add some Sta-Bol into the fuel tank to help keep the fuel "fresh". Other than that, I just accept the loss of fuel due to evaporation.

 

Fuel is draining back to the tank. Either your anti drainback filter in the carb is faulty or the drain back valve in the fuel pump is bad. Either way the electric pump is band aiding one of those two problems.

Quadrajet?

 

How does gas flowing from the carb back to the tank make the fuel level in the tank drop? it would make the tank level rise.....

 

what exactly does Sta-Bil do?

 

Helps in preventing the lower grade, ethanal based fuel from "gelling". I would see a yucky "gel" in the bowls of my lawn mower carburaters when I tried to start them in the spring. The sta-bil helped prevent that. I also now run them dry on their last use before putting them away, but don't do that with the Camaro.

 

Fuel is draining back to the tank. Either your anti drainback filter in the carb is faulty or the drain back valve in the fuel pump is bad. Either way the electric pump is band aiding one of those two problems.

Carb is vented, can't drain back to tank. Gas either evaporates or leaks onto the manifold.

 

I recommend opening the hood and having someone watch the carb as you start up after extended storage. Dry carbs allow gaskets to shrink and floats to stick causing leaks. I started one of mine a while back and found the top of the engine puddled with gas after running it a few seconds. I dryed up everything and let it sit overnight. Next day no leaks and ran fine. Nothing worse than an engine fire in the garage. Ask me how I know?

 

Putting a non vented cap on temporarly for storage should reduce fuel evaporation.

I would also suggest checking rubber fuel line segments from tank to carb and ensure they are snug and make sure there is no slow leak or weaping.