Stinky 63 340hp

[Stuart F.]

I live in Florida now and have a two car attached garage, one port of which is occupied by my 63 340 hp convertible. After one of my usual early morning or evening "heart Therapy" sessions with the car, I return it to the garage and shut it down. For a day or so later my wife complains about the strong stench of gas in the garage. I pretty much know it's due to heat soak/perculation of gas in the AFB as it has always done it. I have had the engine set up stock for show for some time now and prefer to keep it that way, i.e. heat riser butterfly in place and functioing properly, chrome steel fuel line from manifold mounted filter to carb, etc. I've resisted trying to cure or limit this problem by improperly insulating the carb with an insulating base plate or a 300 hp SS heat shield, and perhaps a fuel hose in place of the steel line. As I no longer have a long warm up cycle here in Florida, I'm considering replacing the heat riser butterfly with a Fuelie spacer block, and possibly blocking off the heat riser passages in the intake manifold with pieces of tin plate (like we did in the old days to make more noise and gain power). I recall on some race prepped models from the factory, block off plates were provided for owner/dealer installation. I'd like to hear some discussion on this as to the practicality of doing this or any other method I can employe to make the little woman happy. The engine is all original w/44k on the car. I have maintained it well since new so it is clean inside. I check temps of manifolds and heat risers with a pyrometer and every thing looks w/i normal ranges.

[Michael H.]

Re: Stinky 63 340hp

I live in Florida now and have a two car attached garage, one port of which is occupied by my 63 340 hp convertible. After one of my usual early morning or evening "heart Therapy" sessions with the car, I return it to the garage and shut it down. For a day or so later my wife complains about the strong stench of gas in the garage. I pretty much know it's due to heat soak/perculation of gas in the AFB as it has always done it. I have had the engine set up stock for show for some time now and prefer to keep it that way, i.e. heat riser butterfly in place and functioing properly, chrome steel fuel line from manifold mounted filter to carb, etc. I've resisted trying to cure or limit this problem by improperly insulating the carb with an insulating base plate or a 300 hp SS heat shield, and perhaps a fuel hose in place of the steel line. As I no longer have a long warm up cycle here in Florida, I'm considering replacing the heat riser butterfly with a Fuelie spacer block, and possibly blocking off the heat riser passages in the intake manifold with pieces of tin plate (like we did in the old days to make more noise and gain power). I recall on some race prepped models from the factory, block off plates were provided for owner/dealer installation. I'd like to hear some discussion on this as to the practicality of doing this or any other method I can employe to make the little woman happy. The engine is all original w/44k on the car. I have maintained it well since new so it is clean inside. I check temps of manifolds and heat risers with a pyrometer and every thing looks w/i normal ranges.

Stuart,

The easiest way to eliminate the "after shut down fumes" problem is to leave the car outside of the garage for about an hour to cool down after your cruise.

It may be a lot easier to just secure the heat riser in the open position for street operation instead of removing/replacing it with a spacer. That way, it would be a simple task to return the car to a correct state.

Much of the problem with fuel fumes/evaporation is supposedly caused by todays new fuel. When hot, it evaporates quickly.

I have the same issue with my 66 here in Florida if I park the car in the garage while still at operating temp.

[Duke W.]

Re: Stinky 63 340hp

Try wiring the heat riser valve open as a first step to see if that helps.

Duke

[Gary S.]

Re: Stinky 63 340hp

My 66 did this and my 72 still does it. I consider it normal, especially with today's computer controlled cars with virtually no emissions. Btw, both of my cars were/are Holley equipped if that makes a difference. About the only alternative is to park it outside for a bit, as suggested.

You can always train your mind to think of this as a phermone!

[Stuart F.]

Re: Stinky 63 340hp

I always thought of this as a 63 only problem due to the steel fuel line, and other faulty designs that were corrected as early as 1964, i.e. crankcase ventilation taken from inside of air filter w/o flame arrester, etc. But, it appears as it is much more wide spread throughout the years.
I used to wire open heat risers "back in the day" and use blockoff tin plates as mentioned, but my heat riser on this car is 120 degrees out of position. I let a Corvette shop in Illinois put on a new exhaust system during my post heart surgery "wimpy days" and they assembled it wrong. It works fine, but is hard to get to to tie on a wire. We used to use heavy gauge copper wire. I have intended to at least correct this situation as I have all the parts, and recently picked up an F.I. spacer in case I decide to make it more permanent. I even ground out the butterfly bosses inside to make it less restrictive (round).
I never considered todays fuel as a contributing source of the problem, but it makes sense. I do use Tetra Ethyl lead additive as I am still running 11.25:1 compression and NO hardened valve seats (original engine, never been apart).

[Duke W.]

Re: Stinky 63 340hp

Your engine was double gasketed at the factory and the actual CR is no more than 10.5:1, and with the lazy OE centrifugal advance, it should run detonation free on unleaded premium.

"Hardened valve seats" are not required for normal road use.

There is lots of information in the archives that dispel the various myths about "octane boosters", valve seats, and compression ratio.

Duke

[Stuart F.]

Re: Stinky 63 340hp

I will certainly research the archives to learn more about fuel additives. I do run a re-curved distributor and tall gearing (close ratio w/3.36:1 posi) so I have been concerned about detonation, perhaps overly so. I used to run auto store additives such as 104+, but since finding Jack Podell, I have run the Tetra Ethyl lead additive for perhaps the last 10 or 12 years with good results. I was able to reinstall my aggressive advance curve and kicked the timing back up to 12 initial. I use a Petronix II ignition kit w/ their matching coil, and bypass the ballast resistor with a jumper wire for the system required full 12v input. It seems that the engine runs cooler now in traffic and performs as well as or better than new. Back in those days, with points, I could not go through a downtown w/o fouling a set of plugs and get sluggish throttle response, etc.

[Joe L.]

Re: Stinky 63 340hp

I will certainly research the archives to learn more about fuel additives. I do run a re-curved distributor and tall gearing (close ratio w/3.36:1 posi) so I have been concerned about detonation, perhaps overly so. I used to run auto store additives such as 104+, but since finding Jack Podell, I have run the Tetra Ethyl lead additive for perhaps the last 10 or 12 years with good results. I was able to reinstall my aggressive advance curve and kicked the timing back up to 12 initial. I use a Petronix II ignition kit w/ their matching coil, and bypass the ballast resistor with a jumper wire for the system required full 12v input. It seems that the engine runs cooler now in traffic and performs as well as or better than new. Back in those days, with points, I could not go through a downtown w/o fouling a set of plugs and get sluggish throttle response, etc.

Stuart----


1) If the engine does not have significant pre-ignition on normal pump gas, then you do not need any octane booster, at all. Try it without the booster and see how it runs. No significant pre-ignition= forget about the octane booster; you're just wasting your money using it;

2) You don't really need to add any lead additives. Regardless of whether you have hardened valve seats, or not, your valve seats will last longer than you likely will. If you want to add something to the tank for a little extra protection, use a lead substitute like Alemite CD-2. This contains the active ingredient Powershield. It's very concentrated so you only have to add a few ounces per tankful. I used it for 50,000 miles in my 1969 small block without hardened valve seats, and I experienced not the slightest bit of valve seat recession in that time (based upon later visual inspection of the heads). Of course, it's highly likely that I would have ended up the same way even if I hadn't used the lead substitute. But, I used it so I can't say, for sure, what would have happened if I hadn't. The Alemite is cheap, easy to use, and very safe.

3) Your fuel vapor problems are DEFINITELY not unique to a 1963. To one degree or another, it's very common with just about any carbureted vehicle. Pre-1971 are the worst because there were no vapor recovery systems, at all, installed on cars (except 1970 for California). 1971-81 are a bit better, but there' are still fuel vapors generated. 1982 and later with fuel injection pretty much eliminates the problem. The problem is that folks today are not used to the "gasoline fumes in the garage" syndrome. Back in the 60's, it was just accepted as normal. So, see, emissions controls do have some practical benefit.

[Stuart F.]

Re: Stinky 63 340hp

I just reviewed a very extensive thread from back in 04 dealing with this problem. Seems it is very wide spread, including the long cranks to re start after a week or so of sitting. I too learned to accept that because it was as if you were pre-lubricating the engine. I once tried to move the process along using eyther (sp) spray - BAD IDEA! w/ 11.25:1 compression, I got all kinds of reports from the engine; spark knock, piston slap and maybe rod knock! Never again! I'll let her crank. Pouring gas down the carb is a bad idea too in case you get a backfire!

[Gerald L.]

Re: Stinky 63 340hp

My 63 340 and AFB and its long cranks always concerns me, I don't consider it a valuable prelube, I know others do; it takes is few cranks for the pressure to come up. After a long sit I have been using a carb precharge of 3 oz of gasoline poured down one of the large AFB bowl vent tubes using a Mityvac and 1/4 inch id vinyl tubing; fits right over the AFB brass vents. I try to assure that this gas is as clean as possible as I know it goes thru the jets. To me this is much safer than a spray or gas down the carb throat. Car starts right up.

I have been encouraged to consider a passthru electronic fuel pump but for right now I just live with the problem.

I leave the garage open and the hood up until the engine cools after a drive, typcally do not have lingering gas smell in the garage.

IMO this evaporation happens quickly. I have considered capping the vents after a drive by cross plugging pairs of the four vents with 1/4 inch tubing, but I don't know the effect a slight vacuum will have on the bowls from the cool down. Would be interesting to see the impact of that action but to date I have not gotten around to this experiment.

[Duke W.]

Re: Stinky 63 340hp

The air bleeds will prevent any pressure differential.
Just don't forget to remove the tubes prior to the next drive.

Duke

[Stuart F.]

Re: Stinky 63 340hp

I am always inclined to close my garage door as soon as I drive my Vette in. The main reason for that is that we live on a lake here in Florida and right now we have a gazillion of these little flys all around. I suppose next it will be lovebug season, but it's always something. Also, we have only been down here since 04 and the first local paper I picked up had a story how the vintage Corvettes were the #1 target for car thieves. Guess I'm still a little paranoid and don't want too many to view it in the driveway.

Thanks for the priming suggestions. It has always bothered me to crank for so long due to wear and tear concerns for the starter (I am on #3 starter already - #1 shorted out in August 1963, #2 was stolen by a Corvette shop in Downers Grove, Illinois).

[John H.]

Re: Stinky 63 340hp

since finding Jack Podell, I have run the Tetra Ethyl lead additive for perhaps the last 10 or 12 years with good results.

The Podell stuff is mostly kerosene and alcohol.

[Reed B.]

Re: Stinky 63 340hp

[quote=Stuart Fox (28060);338731]I am always inclined to close my garage door as soon as I drive my Vette in. The main reason for that is that we live on a lake here in Florida and right now we have a gazillion of these little flys all around. I suppose next it will be lovebug season, but it's always something. Also, we have only been down here since 04 and the first local paper I picked up had a story how the vintage Corvettes were the #1 target for car thieves. Guess I'm still a little paranoid and don't want too many to view it in the driveway.



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 B.]

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.