Gas Odor After Parking Vette

[Michael M.]

I Had A Slight Gas Odor After Parking My 68 327/300hp Vette.
After Venting The Garage, Looked For A Leak And Couldn't Find Any. No Signs Of Gas On Intake, around carb, any Lines, Filter, Fuel Pump Etc. Closed Up The Garage And No Odor Reurned.
Took Car For A Spin, Parked It And Same Odor. Could It Be That The Carb Is Dumping Gas Internally To The Intake? Float problem?
I Normaly Park This Car At Another Garage Location And Leave Right After Parking It. I Took The Car Home Overnight And Discovered The Odor. Any Opex or Suggestions Would Be Appreciated. Thanks In Advance

[Stuart F.]

Re: Gas Odor After Parking Vette

Michael;

Welcome to the club of attached garage classic Vette owners. You didn't mention what carb you have, but most will heat soak and vent or spill internally with the new gas w/10% Alcohol. I tried everything with my 63 as the wife was ready to ship me and the Vette out. I have it under control now with a long list of changes including a phenolic spacer under the carb (shows cooler operation by some 35 to 40 degrees), Tomco inlet valves in place of needle/seats which allows me to set the floats lower and a bunch of other items. You can start though by changing one habit, i.e. shut down outside your garage and let it cool for a minimum of 15 minutes, then restart and quickly move it into the garage and kill it again. Keep your garagen door(s) open part way and use a fan if available (I have a ceiling fan). Keep the hood open and do not cover the car for at least an hour. That should bring it under control and make it tolerable.

For certain, check all the essentials too. I tried different caps and found the one you should have (w/two way vent valve - pressure and vacuum) worked best.

Good luck;

Stu Fox

[Roger O.]

Re: Gas Odor After Parking Vette

One fairly common problem on cars that have not had the fuel lines replaced is the lines rust through just under the passenger seat. The lines take 2 90s and go up the frame over the rear wheel. Pinholes leak tiny amounts of gas and never hit the floor and evaporate.

[Jim T.]

Re: Gas Odor After Parking Vette

If your 68 327/300 has the original type QJet carb there is a possibility that the fuel in the carb is leaking into the intake. QJet's have a history of doing this. If you car has to crank and crank after sitting it could be because the fuel leaked out of the carb.

[Daniel N.]

Re: Gas Odor After Parking Vette

I Had A Slight Gas Odor After Parking My 68 327/300hp Vette.

When I had the same problem with my '65, it turned out to be a poorly sealing fuel cap on the gas tank.

[Kenneth T.]

Re: Gas Odor After Parking Vette

After a nice drive with a well warmed up engine, you shut her down and the engine temp will rise and you will have some peculation in the carb. Most times these cars were parked outside as they were just (real nice) transportation, so no issues.
Putting them right into the barn after a drive, you will smell them, as they are carbureted engines. "Rode hard and put away wet" I believe is the term.

Ken

[Stuart F.]

Re: Gas Odor After Parking Vette

Ken;

All true. I think both the pampering of these old cars (always garaged) plus the fact that so many more folks have attached garages now probably adds to the awareness of the problem. As noted on my earlier post, I have fairly well learned to manage the problem. I had to as the wife was about to evict me and the Vette. The phenolic spacer alone cut 35 to 40 degrees temp from the carb (running and after shutdown) which seems to have eliminated the percolation. Also, the 15 minute shutdown outside the garage helps too, along with a period of fan ventilating of the garage with the door(s) part way open once you have parked in the garage, together with leaving the hood open and not covering the car right away.

I would say that even with our mid - 90's weather lately, when I make a run, return, and go through my shut down procedure, I can not smell any gas after a half or 3/4's of an hour - and the wife don't complain any more.

Stu Fox

[Roger O.]

Re: Gas Odor After Parking Vette

Mike , has the car been restored ?

[Joe R.]

Re: Gas Odor After Parking Vette

Ken;

All true. I think both the pampering of these old cars (always garaged) plus the fact that so many more folks have attached garages now probably adds to the awareness of the problem. As noted on my earlier post, I have fairly well learned to manage the problem. I had to as the wife was about to evict me and the Vette. The phenolic spacer alone cut 35 to 40 degrees temp from the carb (running and after shutdown) which seems to have eliminated the percolation. Also, the 15 minute shutdown outside the garage helps too, along with a period of fan ventilating of the garage with the door(s) part way open once you have parked in the garage, together with leaving the hood open and not covering the car right away.

I would say that even with our mid - 90's weather lately, when I make a run, return, and go through my shut down procedure, I can not smell any gas after a half or 3/4's of an hour - and the wife don't complain any more.

Stu Fox

Hi Stuart:

I've been thinking about trying a phenolic spacer for the reasons you mentioned, but I was unsure about the amount of improvement to expect. The 35-40 degree reduction in carb temps that you got sounds good.

How thick is the spacer you are using?

[Stuart F.]

Re: Gas Odor After Parking Vette

Joe;

I'm not sure what model/series you have, but mine is a 63 L-76 (340 hp). I just used a spacer from an L-75 (300 hp) sandwiched by two L-76 base gaskets. The spacer is about 3/8" thick and, as the L-75 also uses an AFB carburetor, the match is a natural. However, I did not use the stainless steel plate that is normally used on the L-75 because I do not have the exhaust heat chamber beneath the carb. I did have to sacrifice the chrome steel fuel line from the filter to the carb in favor of a fuel hose due to the extra height. Also, I eliminated the chrome hot air tube to the choke as well because of the heigth and my preference for an electric choke conversion. It would be possible to make the hot air tube fit or to replace it, but I wanted to save all the original parts as is. Eliminating the steel to steel connections of the fuel inlet line and hot air tube may add some marginal heat isolation as well, but it would be hard to calculate. I just wanted to cover all bets.

My heat calculations were done using an IFR gun, testing typical before and after conditions (running, shut down, heat soak, etc.).

As mentioned in my previous posts on this subject, I also use "Tomco" inlet valves in place of standard needle/seats. This allows me to set the floats down for a slightly lower fuel level to aid the percolation problem. The valves flow better than the needle/seats and, generally, have as good or better fuel control (all mfg. claims asside).

Stu Fox

[Joe R.]

Re: Gas Odor After Parking Vette

Hi Stu:

Thanks for the info. I have a 67 SB with the Holley 3810. The primary fuel bowl on the 3810 exacerbates the hot-soak problem because it has a vent in the top that opens when the throttle is at rest. I don't know if this is really necessary for the 3810, and I have considered disabling it. It appears to have been a short-lived feature on Holley carbs.

In any event, I can literally hear the fuel boiling in the bowls after a hot-soak shutdown, and of course, I can smell the fumes. I think I will try a 1/4 inch phenolic spacer. It seems to me that would likely reduce the carb temp considerably, and your test data appear to confirm that.

[Stuart F.]

Re: Gas Odor After Parking Vette

Joe;

Most all of the early model carbs were vented in some way or another until they devised the emission controls to capture the fumes, so you can't easily get away from that. What you plan otherwise I have found to help a lot, but it is no panacea either. You will always have some venting that you will be able to notice, specially in the closed environment of a garage. The new alcohol laced fuel has only made the problem worse.

Bottom line; I would not alter the venting.

Stu Fox