Stinky 63 340hp

[Joe L.]

Re: Stinky 63 340hp

Reply,
I also have a '63 340 HP Corvette with the garage fuel smell problem. I believe it's due to the fuel pump keeping the 6 pse fuel pressure on the carburetorafter it is shut down. Any small leakage in the carburetor needle & seat will cause extra fuel to be put into the fuel bowls subject to evaportation. There are many bleed holes to the atmosphere in the carburetor (venturi vents, tube stack bowl vents under the air cleaner, throttle shaft leaks, etc.). The gas cap is also vented to the atmosphere, which could be another source of fuel vapor leak/smell.

I would appreciate anyone's solution to the problem, other than letting the car cool down outside the garage. Newer Corvettes have EVAP systems with sealed tanks and canisters to fix it, but what can we do short of this.

Reed-----


Nothing that I know of. This is just the "nature of the beast" as far as old cars are concerned. There's no practical way to eliminate it. This is a great example of how "expectations" change over the years. In the "old days" this fuel odor phenomenon was just accepted. The same thing was true for high HC exhaust emissions. The conditions that people put up with in the 60's and considered "normal" would shock most people today if they were to experience it.

[Stuart F.]

Re: Stinky 63 340hp

Reed;

I have tried some of the suggestions that came with this thread. First, as I intended to do anyway, I wired open my heat riser butterfly. That seemed to help some, at least the smell doesn't persist quite as long. I tried vent loops on the vent tubes (2' foot long sections of clear hose), but that ironically didn't seem to help enough to make the effort worth while.

My carb is not all that old. It is a new replacement 3721SB that has been on there about 10 years (maybe 5000 miles), so I don't feel it is a fault of it. It does have the usual AFB maladies including choke problems (corrosion in pull off), but I'm going to try an electric choke conversion just to eliminate the exhaust heated air into the choke. The chrome steel fuel lines will stay, even though they are a certain source of heat soak to the carb (although I may try a hose from the filter to the carb like a 64). I already have a SS heat shield under the base (allah 300 hp).

Together with today's fuel, I guess I'm fighting a loosing battle, but it's fun to try.

Stu Fox

[Tyler T.]

Re: Stinky 63 340hp

Make sure it does not have a pin hole leak in the tank. Thats what mine was. Install an exhaust fan in the garage. Install an electric fan in the car with a lower, say 160 deg, turn on point. If you have a fridge in the garage keep a few cool packs in the freezer and when you come home and park pop the hood and put a couple on top of the aircleaner.

Tyler

[Stuart F.]

Re: Stinky 63 340hp

Tyler;

Some real good ideas, I specially like the garage exhaust fan. I have been intending to do something about my garage, because it gets so it is too hot and humid out there for me to do anything this time of year. This can't be good for my car or materials that I have out there. the fan may be a good place to start.

I'm fairly sure my tank is sound, but I will check it more carefully. When and if I A/C that area, then I will put a small "Beer" fridge out there, but to do it now I'd have a terrible power user trying to keep things cool.

Thanks again. Always appreciate some fresh ideas.

Stu Fox

[Jack H.]

Re: Stinky 63 340hp

Today's modern cars are exclusively FI based in terms of fuel delivery. That means gas from the tank to the engine is under pressure all the way to the injectors (closed system).

Carb based engines store gas in the carb's fuel bowl and those are intentionally vented to equalize pressure to atmospheric prior to mixing in the venturi. Hence, when you shut down the engine, underhood temperatures climb as a result of coolant flow stoppage and the fuel in the carb's fuel bowl WILL climb.

Combine the rising fuel bowl temp with the fact they're vented to the atmosphere and you CAN expect some out-gassing of fuel vapor. That's life with these cars...

Back when they were originally made/sold, the norm was for a garage to be detached from the house. And, we quickly forget what the old auto technology was like, comparing things to current era norms.

Another aspect of these cars that can increase fuel odor, is an owner's propensity for 'topping off' the gas tank just prior to storing the car in the garage. That will rob the gas tank of expansion space for fuel vapor to accumulate during the engine shut down, underhood temperature elevation period.

It's often the wife who complains of fuel odors in the garage as she's somewhat warry of the classic 'old' car that hubby 'put together', nervous that it might be a fire hazzard (CAN be!) and is making an unfair comparison of yesterday's technology to today's technology.

YES, there can be cases of improper venting and fuel line breach that warrant IMMEDIATE correction. But, with a well restored car, it's more often a case of unfair expectation, especially in warm weather climates with attached garage home construction...

[Stuart F.]

Re: Stinky 63 340hp

AMEN Jack;

I agree with all you say, specially about the wife's concern. We live here in Central Florida where currently our normal ambient is 92 to 97 degrees, and we too have the attached garage. As for me, I don't expect to cure the problem short of getting rid of the car - and that ain't gonna happen while I'm still kicking. I only hope to improve on it. What I do is let it idle for a short time outside the garage and let it normalize while I do my IR gun temp checks, and look for leaks, etc. Then I drive it in and open the hood, leaving the garage door open a while longer. Not wanting to give it too much exposure, I immediately roll my garbage bin and a BBQ behind it which pretty well hides it to passers by. With that, and the heat riser change, I think I have reduced the problem some. Leastwise, the wife doesn't complain so much - and that's the true test.

Stu Fox

[Timothy B.]

Re: Stinky 63 340hp

I can't comment on the aluminum manifolds but on my 63 300HP car the heat slot is blocked in the cast manifold under the carburetor and this makes a huge difference in gasoline temperature. It still stinks and get hot but not like before.

The 340 aluminum manifold is a heat path to atmosphere so the manifold always appears very hot but it's only doing what it is designed to do. I wonder if one of those spacers like on the 300 HP would help and if there is room with the hood. It seems to me that the thin carburetor gasket between manifold and carburetor would not keep the aluminum carburetor from heat soak with the aluminum manifold. Also, I bet yesterday's gas is much more tolerant or this heat. (FWIW)

[John D.]

Re: Stinky 63 340hp

Stu, First problem is you live in the swamp.
As you know I have a 63 FI car known as the LWC. Recently after running it for a spin around the neighbor hood with an illegal plate I brought it home and immediately brought it into the AC garage and closed the door as it started to rain. Naturally evey time the car goes out it rains. So I was wiping it off and after a short while I noticed some gas fumes. But they were sweet smelling fumes as 100LL AV gas burns sweet.
Not going to say the solution of the problem is 100LL as that will cause an extra 100 posts. Just going to say the LWC fumes don't smell.
Bad news a comin in PA though. Our governor went on TV with a big smile on his face braggin about how he was gonna solve some of the problems of the high price gas and the economy. Ethanol. Our own home grown corn to be used to help brew crapola gas. Ethanol in every station in the state of PA. Yuk. Can't print what I am thinking.

[John D.]

Re: Stinky 63 340hp

The Podell stuff is mostly kerosene and alcohol.

Can't be that bad if it has alcohol.

[Christopher R.]

Re: Stinky 63 340hp

Jeez, Stu. Can't leave the car out because of the bugs, and crime. Can't work on it because it's 92-97 degrees F.

Move to a city in the Northeast where the people are nice and the weather changes. I live in a residential city neighborhood. My car's been out of the garage and sitting in the driveway since I put the engine in Thursday. I can't move it back into the garage by myself because it's up a slight incline. It's been like a block party here. Neighbors keep coming over and telling me their car stories. ("My ____ had one like that once.") Weather has been in the mid 60s at night, mid-80s during the day. Low humidity. (To be fair, it was hot and humid last week for a few days. Had to use the air conditioning. Quelle horreur!))

'Course you'll be driving this Winter, and my car will be in the garage.

[Joe R.]

Re: Stinky 63 340hp

OK, maybe we 6 cyl guys can have their day in court.......

I also have had this experience with fuel vapors and the disturbed wife. Insofar as the 54 Blue Flame Six is concerned, I too experienced the strong smells after a run on a hot day here. I lowered the float levels in my carbs by 1/4" (yes, all 3 of them!) and MOST of my vapor problems went away. The ambient here in the So. Cal. desert is now about 101 Fahrenheit, and I can park her in the garage with greatly reduced fuel smell. Maybe Duke can explain my experience with a more scientific approach, but it worked for me. It (the lowered floats) also permanently resolved my occasional venturi drip issue (these are side drafts, fyi).

Just my $0.02.

Joe

[Duke W.]

Re: Stinky 63 340hp

If fuel dripped out the main nozzles after shutdown then the float levels are too high or the needles/seats leak. Any residual fuel that drips out the main nozzles after shutdown will evaporate and contribute to fuel odor. It can also cause hard hot starting.

Duke

[Stuart F.]

Re: Stinky 63 340hp

Christopher;

I think a lot of our crime problem is due to your NE rejects. They like it hot and want everything for free.

It's not as bad as it sounds. It's just I am a little paranoid. This is probably my one and only Vette - it's been my baby for 45 years. Perhaps I should follow my son's advice and trade it even up for a new C-6 w/air and full power, etc. and enjoy life. I don't know.

Stu Fox

[Wayne K.]

Re: Stinky 63 340hp

Stuart,

I feel your pain. It is a common calamity with woman just like menopause. My wife named our car stinky after the first time I parked in the garage after a pleasure drive. Since then I try to leave it out until cool but even then with the open venting and modern gas it is impossible to avoid. She has been nagging me about the smell for years and now that she is experiencing the hot flash syndrome the nagging has gotten to the point that I have put the car up for sale. I hope you don't have to come to that decision.

Wayne

[Stuart F.]

Re: Stinky 63 340hp

Wayne;

Fortunately, I don't think it will ever come to that with me. Over the years (43) there have been a number of times when I considered selling the car, but it was my wife is the one who talked me out of it. She, even now, considers it a member of our family. Our sons have grown and left, and one has a Vette of his own. They too grew up with our 63 and put in a lot of time helping their Dad with it. I never heard them ever say we should let it go.

The main thing for us is as long as I am trying to do what I can to help the problem, that seems to mean a lot. Then too, I have a hat that says; "Man Law says; Never, Ever give up the garage". I wear that every now and then to reinforce my position. Got that one from Crackle Barrel.

Stu fox