Stinky 63 340hp

[Stuart F.]

Re: Stinky 63 340hp

Duke;

My crankcase explosion occurred during a start-up after a lengthy storage of the car when I got back in-country. It was below zero in January and the car was stored in a garage with the cylinders packed with Wynn's Friction Proofing and valves collapsed (was popular method back then). We had set the valves, removed the plugs and turned it over to pump the cylinders out, changed the oil, new points/condensor & plugs - but we never touched the PCV valve. Therein lay the problem. It apparantly was stuck open and during the long crank to start, fuel vapors were allowed to circulate back through the system from the air cleaner to the crankcase. When the engine fired, so did the fuel vapors in the crankcase - off came the valve covers and the choke tubes, hitting the low ceiling and bouncing around. It was a sight to behold. We just laughed, what else could we do. It is the story I like to tell people at shows to explain my replacement valve covers (with the parting lines through the "O").

I thought my experience was unique until I noticed the "Advance Information" Technical Service Bulletin A.I. 63-10 re-printed in the latest J.G. P.216. It describes exactly how it happened to me, and shows a "Flame Arrestor Screen Installation" (which I still won't do as I don't want any potential loose parts in my air cleaner - thank you).

My theory was bolstered by the fact that later designs moved the clean air inlet to a separate "hog hair type" filter/tube "outside" the main air filter element, probably to limit the potential for drawing in fuel vapors.

My current shut down procedure includes removal of the air cleaner (that chrome heat reflector) and blowing an 18" fan over the engine. I also like the "screw-in/out" fuel petcock idea for in my fuel hose between the fuel filter and the carb - as long as I have a hose there now.

I tested the fuel pressure output of my pump, and it's a shade under 6 psi. The data I have on Viton tipped needle/seats used in AFB's shows them good to 6.5 psi. The Tomco valves claim up to 8 psi.

Thanks as always for your valuable assistance. I would join the chorus of the current thread thanking you, but it is getting a little mushy and I'd sooner stay at a level of Professional Respect.

Have a great day.

Stu Fox

[Michael H.]

Re: Stinky 63 340hp

Michael;

As mentioned, I will really get into this now with my I.R. gun so I can find out what is happening. I'll keep you posted.

GO SOX!!

Stu Fox

So, did I win, did I win? Was I first with the correct answer?

May be difficult to see much temp change on the outside of the carb casting with the IR gun during heat soak after the hot engine is shut off but it's possible. I'd be interested.
Guessing, I would say most of the heat difference would probably occur at the bottom of the bowl instead of the outer surfaces.

[Joe L.]

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).

Stu-----


I really doubt that modern gasoline is the cause of your problem. The volatility of gasoline as measured by Reid Vapor Pressure (RVP) has actually been substantially reduced over the years due to EPA/emissions requirements. EPA allows a slightly higher RVP for fuel with 10% ethanol content (which much modern fuel contains) but even with the higher RVP allowed for 10% ethanol fuel, it's still way lower than the RVP was in the 60's. So, modern gasoline should tend to ameliorate your problem rather than exacerbate it.

[Michael H.]

Re: Stinky 63 340hp

Stu-----


I really doubt that modern gasoline is the cause of your problem. The volatility of gasoline as measured by Reid Vapor Pressure (RVP) has actually been substantially reduced over the years due to EPA/emissions requirements. EPA allows a slightly higher RVP for fuel with 10% ethanol content (which much modern fuel contains) but even with the higher RVP allowed for 10% ethanol fuel, it's still way lower than the RVP was in the 60's. So, modern gasoline should tend to ameliorate your problem rather than exacerbate it.

I dunno. Problem goes away in my car when I use racing fuel, which I do about two times a year. No ethanol. I have to guess aviation fuel would be the same.
With "street fuel", I have the exact same problem that a LOT of other people are having. The carburetor is dry within about three days if I park the car while at operating temp.
That never happens with fuel without Ethanol and it didn't happen years ago when street fuel didn't have it.

I think the boiling point is lower with the new fuel mixes. The evaporation rate may be lower at room temp but I bet it isn't lower at 200*.

[Stuart F.]

Re: Stinky 63 340hp

Duke, Joe, Tim, Michael, Jerry and all the others who have contributed on this thread;

Thank you all for your valuable ideas and suggestions. I guess it's time to put this thread to bed before it goes to a third page. I should not presume that this subject deserves so much study and detail analyses. I took my Q's from no less than a half dozen 63 340hp owners who seem to be having the same or similar problems as I, and have taken the time to send me Private Messages and E-Mails to more fully describe their experiences. I know I have learned a lot from this excercise and I hope it was of value to some others as well.

I've compiled a lot of notes and data which I may put together and bounce it off some of you to see if you think it is worth at least a paper or article of some sort. Probably not, but it has been fun and it keeps me busy.

Regards to all;

Stu Fox

[Dale C.]

Re: Stinky 63 340hp

I guess I'm crazy, but I just love that smell. It means I've been out driving my car and got it home and safely and in the barn again. Tell your wife its her car that dosen't smell right.
Dale 33147

[Michael H.]

Re: Stinky 63 340hp

Duke, Joe, Tim, Michael, Jerry and all the others who have contributed on this thread;

Thank you all for your valuable ideas and suggestions. I guess it's time to put this thread to bed before it goes to a third page. I should not presume that this subject deserves so much study and detail analyses. I took my Q's from no less than a half dozen 63 340hp owners who seem to be having the same or similar problems as I, and have taken the time to send me Private Messages and E-Mails to more fully describe their experiences. I know I have learned a lot from this excercise and I hope it was of value to some others as well.

I've compiled a lot of notes and data which I may put together and bounce it off some of you to see if you think it is worth at least a paper or article of some sort. Probably not, but it has been fun and it keeps me busy.

Regards to all;

Stu Fox

I think that this will become a larger and larger issue as the months pass and I agree, an article in the Restorer would be an excellent idea.
The same problem has been affecting the FI cars too and, again, the only thing that has changed in the last decades, is the fuel. (they've always had that problem but no where near as severe as in the last few years)

I'm stickin with my perc/boil theory, even if I'm alone with it. I think, at the very minimum, fuel in the bowl is turning into a gas/vapor and condensing at the end of the booster.

[Gerard F.]

Re: Stinky 63 340hp

I'm stickin with my perc/boil theory, even if I'm alone with it. I think, at the very minimum, fuel in the bowl is turning into a gas/vapor and condensing at the end of the booster.

Michael--

That's the way my grappa still works. I get the best stuff out at 180-200 degrees F, around 125 proof on the first run. If I let it get over 200, I start pulling too much water vapor and it dilutes.

I can see a carburetor acting somewhat like a still, sitting there cooking after a hot shutdown. Especially with ethanol in it.

Cheers,

Jerry Fuccillo

[Stuart F.]

Re: Stinky 63 340hp

Michael, Dale and Jerry;

Just some final thoughts on this matter;

1) I guess I wouldn't be so concerned about the smell except I have seen the puddles of gas in my manifold beneath the primaries, and my local Auto Parts store refused my last drain oil due to it smelling like gas. You've got to know much of that gas is washing down some cylinders and finding it's way to the crankcase - dilluting the oil. Although probably not enough to cause a hydraulic lock on the carbureted engine (unlike the Fuelie), but still it can't be good. Before I can go to the OctoberVette show this weekend, I feel I must recharge my Rotella.

2) The wife is coming home today from an extended visit to Chicago. I have to stop my experiments and de-fumigate the garage as well as wash my clothes and sweat rags. It got to the point where the smell was on my hands and transferred to my clothes, in my hair, and even on the dog. I usually drive into the garage before we get out of the car, but today I'll drop her off outside as it is easier to take her bags in through the front door. Now, we're talkng a serious matter here - agreed? Ha!

Stu Fox

[Brian K.]

Re: Stinky 63 340hp

I have this problem on my 66 327/300 even if the car sits for a week. Happens with full tank or 1/4 tank. I can't see anything wrong with the fuel system and just consider it normal with the fuel in the bowls, and gas cap vented to atmosphere.

Am I wrong or should I be looking for a problem?

[Chuck R.]

Re: Stinky 63 340hp

Let it cool off outside for a half hour or better prior to parking it so it can percolate and air out with a little help from mother nature.

Chuck

[Stuart F.]

Re: Stinky 63 340hp

Brian;

It just depends how severe it is. I believe I have always experienced some evaporation while the car has been sitting, specially for a week or more. Also, I've always had some level of drive ability problems when the engine was hot, specially on restart in hot weather, etc. It is the nature of the beast. And the gas smell, always to be expected with a vented fuel system, but of late (past few years or so), it has gotten much worse. The car hasn't changed that much, only that now Im living in Florida and we know the gas HAS changed.

My worse case scenario is right after a drive, I put the car away in the garage under cover and after a short period (heat soak), the entire garage smells terribly. As soon as you open the door from the house to the garage it almost knocks you over. That in itself was cause enough for me to investigate how I might improve the situation.
- Upon inspection (removal of air cleaner), looking with a light into the carburetor, I could see a steady stream of fuel coming from each primary main tube in the venturi cluster (not a drip, but a stream). This of course puddles on your throttle plates and leaks down into the intake manifold (throttle plates are cracked open slightly at idle).
- Upon removal of the carburetor from the manifold, one notices a series of grooves or ribs in the inner part of the manifold immediately below each throttle plate. On mine, these were full of raw gas and it doesn't take a rocket scientist to figure out that the gas that doesn't evaporate will pass some open intake valves and either wash down the cylinder walls into the crankcase (in time) or build up enough within a cylinder to cause a hydraulic lock (bend a rod) on the next restart.
- As mentioned before, my local Auto Parts store would not accept my last drain oil because they could detect gas in the oil. I had an oil analysis done and it was indeed found to be contaminated. This, needless to say, is an intolerable situation. It is no longer just a nuisance.

If I were you, or anyone else with a C-2 or any model w/o a closed fuel evaporation system, I would inspect it closely to make sure you don't have a more severe problem (like mine). It can lead to serious engine damage.

Stu fox

[Gerard F.]

Geez Stu, that sounds like my wife

She has a nose on her that can smell gas, oil, cigarette smoke, etc, on my clothes from 30 yards away. She is particularly sensitive to the sweet smell of WD40

Luckily, I have a detached garage and shop where I store the Corvette and do all my projects:

http://img238.imageshack.us/img238/9835/luggageracksmalllc5.jpg

It has a swamp cooler on it, which I guess wouldn't work well in Florida.
But still when I come in the house, I get that Phew sign with the waving of the hand in front of the nose.

Also lucky, that my wife doesn't get on this forum

[Brian K.]

Re: Stinky 63 340hp

Brian;

It just depends how severe it is. I believe I have always experienced some evaporation while the car has been sitting, specially for a week or more. Also, I've always had some level of drive ability problems when the engine was hot, specially on restart in hot weather, etc. It is the nature of the beast. And the gas smell, always to be expected with a vented fuel system, but of late (past few years or so), it has gotten much worse. The car hasn't changed that much, only that now Im living in Florida and we know the gas HAS changed.

My worse case scenario is right after a drive, I put the car away in the garage under cover and after a short period (heat soak), the entire garage smells terribly. As soon as you open the door from the house to the garage it almost knocks you over. That in itself was cause enough for me to investigate how I might improve the situation.
- Upon inspection (removal of air cleaner), looking with a light into the carburetor, I could see a steady stream of fuel coming from each primary main tube in the venturi cluster (not a drip, but a stream). This of course puddles on your throttle plates and leaks down into the intake manifold (throttle plates are cracked open slightly at idle).
- Upon removal of the carburetor from the manifold, one notices a series of grooves or ribs in the inner part of the manifold immediately below each throttle plate. On mine, these were full of raw gas and it doesn't take a rocket scientist to figure out that the gas that doesn't evaporate will pass some open intake valves and either wash down the cylinder walls into the crankcase (in time) or build up enough within a cylinder to cause a hydraulic lock (bend a rod) on the next restart.
- As mentioned before, my local Auto Parts store would not accept my last drain oil because they could detect gas in the oil. I had an oil analysis done and it was indeed found to be contaminated. This, needless to say, is an intolerable situation. It is no longer just a nuisance.

If I were you, or anyone else with a C-2 or any model w/o a closed fuel evaporation system, I would inspect it closely to make sure you don't have a more severe problem (like mine). It can lead to serious engine damage.

Stu fox

Thanks Stu,

It doesn't knock you over & I don't have a percolating or oil contamination issue. But you do smell it slightly in the basement (attached garage) and when you walk into the garage it's stronger. No one has complained, but a friend came over & commented on the smell. Both cars (67 SS Chevelle & the Vette) had been sitting idle for a week.

I am going to rebuild the carb this winter just because it's 20 years old but other than that, I have no operating issues.

I just think that in a cool garage, how much expanding & contracting does a tank do to expel any fumes to atmosphere (assuming no operation in the last 24 hours or so)?

Brian

[Michael H.]

Re: Stinky 63 340hp

- Upon inspection (removal of air cleaner), looking with a light into the carburetor, I could see a steady stream of fuel coming from each primary main tube in the venturi cluster (not a drip, but a stream). This of course puddles on your throttle plates and leaks down into the intake manifold (throttle plates are cracked open slightly at idle).

Streaming sounds a little more serious than dripping. I wonder if the fuel in the steel pump to filter fuel line is expanding and forcing the needle/seat open, over filling the bowl? The expanding fuel in the line AND the boil in the carburetor would certainly be a double header.