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Boiling Gas
Posted by: Intrinsic ()
Date: July 29, 2019 07:05AM

I have an 'RG' code engine in my Rampside. Over the weekend I took the truck for a long drive, and popped open the hatch when I stopped. Several minutes after shutting the engine off, one carb gurgled and ejected about a tablespoon of gasoline. The gas emerged from around the cork gasket which seals the air cleaner to the top of the carb.

I believe that I am experiencing heat sink, and that the gas is boiling in the carb bowl.

Is there a phenolic spacer under the carb, or some other method of controlling the engine heat transfer to the carb?

Thanks

1963 Rampside Standard
1970 VW Type III Fastback
Atlanta, GA

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Re: Boiling Gas
Posted by: BobV66Vair ()
Date: July 29, 2019 07:18AM

Clarks sells thick isolators for exactly this purpose. Be sure to buy double the number of gaskets. You need one above and below the isolator.

Bob Vinnacombe
Sandy, Oregon
1965 Corsa 140 stock
1966 Monza Soon to be race car
1968 Monza Parts for now

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Re: Boiling Gas
Posted by: TerribleTed ()
Date: July 29, 2019 09:40AM

There should be carb spacers under both carbs.

---------------------------------------------------------------------------------------------------------

Avid Corvair hobbiest since 1984.
I have personally performed ground up restoration on over 20 Corvairs.
I currently work full time at restoring and repairing Corvairs.
Located in the Atlanta Georgia area.
[www.facebook.com]

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Re: Boiling Gas
Posted by: Brizo ()
Date: July 29, 2019 02:09PM

Intrinsic, I've had double phenolic spacers under all four carbs on my 140 Greenbrier for 30 years. I worked very well until Gasohol came out. Now, if it's parked with the heads at full temp on a hot summer day day, I can smell gas vapor pouring out of the side air louvers for hours and its sometimes hard to start after setting for only two days. Being a 140 increases cranking time because the fuel pump must fill four carbs rather than two. Having a rubber seal around the engine cover to keep noise down makes things worse because it holds the heat in and heat rising through the fan is directed right at the carbs. Opening the access door for a few hours helps-- but you shouldn't have to do that--and remember to close it. A good fix for being hard to start after the carbs have dried up would be an electric fuel pump with a prime function control module. A/O fuel injection.

Dan Brizendine,
'64 8door Greenbrier 140 PG. "In beautiful Wanamaker Indiana...with one stop light and 5 pizza shops"



Edited 1 time(s). Last edit at 07/29/2019 02:09PM by Brizo.

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Re: Boiling Gas
Posted by: CorvairHaven ()
Date: July 29, 2019 07:50PM

BobV66Vair Wrote:
-------------------------------------------------------
> Clarks sells thick isolators for exactly this purpose. Be sure to buy double the number of gaskets. You need one above and below the isolator.


Seems to me that there has been quite a debate about whether the gaskets are needed or not for the phenolic spacers.

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Re: Boiling Gas
Posted by: American Mel ()
Date: July 29, 2019 09:07PM

CorvairHaven Wrote:
-------------------------------------------------------
> BobV66Vair Wrote:
> -------------------------------------------------------
> > Clarks sells thick isolators for exactly this purpose. Be sure to buy double the number of gaskets. You need one above and below the isolator.
>
>
> Seems to me that there has been quite a debate about whether the gaskets are needed or not for the phenolic spacers.


There has been a lot of people insisting that they are not needed, but for the small price of a gasket, why not?
For one thing, the current spacers are NOT made out of the same material as the old original ones were.
Supposedly they are more heat resistant, but one thing I can tell you is that they are a cheaper material!
The new ones are definitely brittle.
I had some new ones on my car that were not very old and when I removed the carbs, they practically crumbled.
Yes, I had bought them from our favorite BIG Corvair vendor.
As for gaskets, an ounce of prevention is worth a pound of cure, so I've been told.

-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
WA. state, 1 mile south of the Canadian border,
I am not at the end of the world, but you can see it from here.
Have; '66 Monza Coupe - 140, 4-spd. Daily driver beater
'67 Monza Vert. - 140, 4-spd. Daily driver beater
'67 A/C Moredoor Monza
Have had; '61 Monza coupe, '62 Monza Wagon, '63 Spyder, '65 Corsa
.
non-vair
'04 Dodge Cummins Quad Dualy, approaching 400K
17'Terry

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Re: Boiling Gas
Posted by: JimBrandberg ()
Date: July 30, 2019 04:42AM

I use the thin gaskets above and below the blocks with a little Syl Glyde grease. It gives me the good feeling and is one less thing to worry about.
You definitely need the insulator blocks, or more as related above.

Jim Brandberg
Isanti, MN
CorvairRepair.com



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Re: Boiling Gas
Posted by: idiyaught ()
Date: July 30, 2019 05:02AM

Most carb bases are not flat so gaskets are needed.

John Oostdyk
Thornhill, Ont
63 Rampy
65 Greenbrier
64 Convertible

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Re: Boiling Gas
Posted by: azdave ()
Date: July 30, 2019 05:17AM

CorvairHaven Wrote:
-------------------------------------------------------
> Seems to me that there has been quite a debate about whether the gaskets are needed or not for the phenolic spacers.

No debate in my opinion, I have several original GM Delco carb rebuild kits still sealed in the packages (the ones with the plastic viewing window in the parts tray). Those kits always include two thin paper gaskets to go above and below the phenolic spacer.

Dave W. / Gilbert Arizona
65 Corsa 140/4
66 Corsa 140/4
66 Corsa 140/4 w/factory A/C
66 Corsa 455 Toro V8
65 Monza Convertible 110/4
66 Monza Convertible 140/4 A/C
65 Monza 4DR 140/PG w/factory A/C
65 Monza 4DR EJ20T/5



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Re: Boiling Gas
Posted by: Lane66m ()
Date: July 30, 2019 05:27AM

I used the Clark's thick carb gasket under the phenolic spacer and a thin one on top on my More Door carbs' install. Still have the hot engine starting issue. Now I am putting a electric fuel pump momentary switch on the dash to prime the carbs. If that does improve the situation, I will look at thermostat controlled fan to bring cool air in when engine is shutdown.

Al Lane
Ellabell, GA 31308

1966 Monza Coupe, 110 hp, 4 Spd
1966 Monza More Door 110 hp, PG
1968 Camaro SS Coupe 350 CI 295+ hp PG
1964 Greenbrier Deluxe, 6 dr, 80 hp car engine, PG
1947 Farmall A tractor 15 hp


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Re: Boiling Gas
Posted by: Intrinsic ()
Date: July 30, 2019 05:45AM

Its an interesting observation about engine heat rising into the top of the engine bay, via the stationary fan, post engine shutdown.

On my air cooled Type III VW, the entire cooling and combustion air intake air path is ducted and sealed using large rubber bellows to allow for engine movement. I had never considered how this sealed duct arrangement controls the flow of hot air out the louvers on the side of the car, after the engine is shut down and the fan is stationary. Its a clever solution to keeping the hot air out of the top of the engine bay.

I already have an electric fuel pump, and I will check to see if I have the spacers. The VW has a similar phenolic spacer with remarkably thin paper gaskets bonded to the spacer. I wonder how the gasket thickness affects the performance of the spacer?

Thanks for the very interesting and helpful discussion.

1963 Rampside Standard
1970 VW Type III Fastback
Atlanta, GA



Edited 2 time(s). Last edit at 07/30/2019 05:48AM by Intrinsic.

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Re: Boiling Gas
Posted by: gregb ()
Date: July 30, 2019 06:16AM

I use the spacers and thick gaskets on my Corsa and as Jim suggested, grease the gaskets as well. I have never had the issue you refer to but mind you it never gets over 90 where I live. The nice thing about the grease is it if you need to remove a carb for any reason the gaskets don't stick and cleanup of the spacers is a breeze.
Have your heads been de-flashed?? I noticed a big improvement in temperatures after doing that.

Gregb

Alberta Canada
61 Canadian Lakewood
62 Spyder Triple Black Convertible
65 Corsa Coupe

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Re: Boiling Gas
Posted by: JimBrandberg ()
Date: July 30, 2019 07:58AM

I've always thought the fuel percolation after engine shut-down was because the carburetor is perched atop the hot cylinder head. I hadn't thought about hot air coming up past the fan and heating the entire room. Especially in the FC room where heat rises and just can't go any higher up and out.
What about a cross ventilation fan that clears the room and is shut off in a few minutes by a timer.
Opening the access door sounds like a good idea. Hopefully you don't take someone's cat home with you.
Of course running the engine long enough after a workout to cool down is good for valve seat retention.

Jim Brandberg
Isanti, MN
CorvairRepair.com



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Re: Boiling Gas
Posted by: Lane66m ()
Date: July 30, 2019 03:17PM

I had the issue after a 40 mile run at 60 mph, 10 minute run through town at 30 - 45 mph. Pulled in to gas up and shut down engine. Refused to start 8 minutes later after filling tank.

So allowing engine to cool down by low speed / rpm operation didn't help situation. It was a 85 degree day. When cold engine, it starts immediately after one pump of accelerator to set choke.

Now, if I don't start it in 4 or 5 days, it is difficult to get to start up. Several pumps of accelerator and listening to fuel pump to make sure it is working will get it going. That is the 2 reasons I am putting in a momentary prime button.

Al Lane
Ellabell, GA 31308

1966 Monza Coupe, 110 hp, 4 Spd
1966 Monza More Door 110 hp, PG
1968 Camaro SS Coupe 350 CI 295+ hp PG
1964 Greenbrier Deluxe, 6 dr, 80 hp car engine, PG
1947 Farmall A tractor 15 hp





Edited 1 time(s). Last edit at 07/30/2019 03:20PM by Lane66m.

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Re: Boiling Gas
Posted by: joelsplace ()
Date: July 30, 2019 03:23PM

Al, In your situation I've never had an issue but I do have to hold the throttle wide open because it is flooded from the gas boiling over.
On one car I have that vapor locks when I'm in the situation you described I hold it wide open to start it but then it quits shortly afterward when the carburetors run dry from the fuel pump not working.
P.S. never boil gas over an open flame - use an electric stove

Joel
Northlake, TX
5 Ultravans, Lost count at 100 Corvairs...

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Re: Boiling Gas
Posted by: Lane66m ()
Date: July 30, 2019 03:36PM

Yep. That is what i figured out once it started. Lots of black smoke. Had to use starting fluid to help it fire off. So the prime button will help both situations. Use prime button to pump the carb bowls full. One pump for cold engine start. To the floor for a hot engine start.

Al Lane
Ellabell, GA 31308

1966 Monza Coupe, 110 hp, 4 Spd
1966 Monza More Door 110 hp, PG
1968 Camaro SS Coupe 350 CI 295+ hp PG
1964 Greenbrier Deluxe, 6 dr, 80 hp car engine, PG
1947 Farmall A tractor 15 hp


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Re: Boiling Gas
Posted by: Brizo ()
Date: July 30, 2019 07:52PM

Brizo Wrote:
-------------------------------------------------------
> Intrinsic, I've had double phenolic spacers under all four carbs on my 140 Greenbrier for 30 years. I worked very well until Gasohol came out. Now, if it's parked with the heads at full temp on a hot summer day day, I can smell gas vapor pouring out of the side air louvers for hours and its sometimes hard to start after setting for only two days. Being a 140 increases cranking time because the fuel pump must fill four carbs rather than two. Having a rubber seal around the engine cover to keep noise down makes things worse because it holds the heat in and heat rising through the fan is directed right at the carbs. Opening the access door for a few hours helps-- but you shouldn't have to do that--and remember to close it. A good fix for being hard to start after the carbs have dried up would be an electric fuel pump with a prime function control module. A/O fuel injection.

To add to the above, you notice I never mentioned being hard to start hot- its not ever! If yours is hard to restart after parked hot for a little while, its not just percolating, its flooding over. Percolation vapor should all go out the carb base vents. Watch your carbs after a hot shut down and see if any drip from the venture cluster. Vapor lock on Corvairs usually occurs because the fuel pump vacuum is weak or wont hold between strokes. Of course high fuel pressure makes all this worse.

Dan Brizendine,
'64 8door Greenbrier 140 PG. "In beautiful Wanamaker Indiana...with one stop light and 5 pizza shops"



Edited 1 time(s). Last edit at 07/30/2019 07:53PM by Brizo.

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Re: Boiling Gas
Posted by: joelsplace ()
Date: July 30, 2019 08:18PM

This discussion gave me an actual reason to install just an electric pump. You could turn it off when you were close to parking it and run the fuel out of the carbs. Problem solved except for 140s unless they have a single carb installed.

Joel
Northlake, TX
5 Ultravans, Lost count at 100 Corvairs...

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Re: Boiling Gas
Posted by: jjohnsonjo ()
Date: July 31, 2019 06:22AM

Part of this is not just the carbs. The fuel in the lines expands as well. There is enough pressure to override the floats. This is where the fuel return is helpful, this added pressure is routed back to the tank. Also when you restart the car the fuel in the lines cools down much faster. I have a switched electric and the mechanical installed. If I do a hot start with the electric on, you can feel the lines cooling down even at idle. If I am in a safe place I just open the hood while its parked, that's the easiest solution for me. Turbo car.

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa


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Re: Boiling Gas
Posted by: Intrinsic ()
Date: July 31, 2019 06:59AM

Thanks for the advice on percolation, I have never noticed a hard to start circumstance. I will have to check the temperature and pressures of my fuel lines post shutdown.

When I got the truck I discovered that the PO had mis-wired the coil, bridging the running and cranking circuits to the coil, in 3 places no less! Once I set that straight it starts readily.

Great discussion!

Thanks

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