heating problems

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dutchair
Posts: 64
Joined: Sun Apr 12, 2015 4:19 am

heating problems

Post by dutchair »

hello forummers,

I've got a problem with the heating of my corvair.

when I drive about 15 miles with my Corvair with a temperature of 25 celsius the engine stops because of the heat.
It seems that the gasoline evaporates before it reaches the cylinders. (carburetors also become very hot)

My questions is, how can I prevent this ? all seals and engine sheet metal are in place (the engine had a rebuild last winter) i've heard that one thing to prevent this is placing carburator insulators ? ) I don't know if that's been done, probably a standard seal.

what also might help (of what i've heard) is to displace the coil, and make sure that the right coil has been mounted. but that doesn't make sense to me because it has nothing to do with the gasoline ?

can anyone give me some answers ? because this is pretty irritating :angry:

thanks, gr, dutchair

corvair500
Posts: 208
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Location: Virginia

Re: heating problems

Post by corvair500 »

You absolutely need the insulator ( G.M. part 3787453 ) under each carb . If yours are missing , get these from your favorite supplier and install them

corvair500
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Re: heating problems

Post by corvair500 »


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bbodie52
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Re: heating problems

Post by bbodie52 »

NOTE for USA: 25°C = 77°F :USA:


I wanted to make sure that some important insulators were not accidentally omitted when your car was worked on in the past…

Carburetor rebuild kits often contain a thin gasket to seal the underside of the carburetor where it mounts on the intake manifold. The Corvair carburetors need a plastic insulator to isolate the base of the carburetor from the intake manifold, which prevents the gasoline inside the carburetor from boiling or vaporizing if excessive heat is allowed to transfer from the hot aluminum intake manifold on the cylinder head to the carburetor body. These plastic insulators can be easily damaged when removed. Clark's Corvair Parts bundles gaskets and insulators together. They are listed near the top of page 56 in the catalog http://www.corvair.com/user-cgi/catalog ... ow_page=56.

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:angry: If the insulators are not present, and only a single gasket is being used under each carburetor, the fuel may be close to boiling when the car is driven. The use of fuel may allow some effective cooling of the fluid in each float bowl as fuel is consumed and replaced with cooler liquid from the tank. But when the engine is shut down the remaining heat from the heads may continue to heat the gasoline in the float bowls of the idle engine, causing the gasoline to percolate and appear as it drips from the venturi cluster in each carburetor. :evil:

FYI: Here is a method of cooling gasoline that was added to Corvairs when SMOG pumps came on the scene...

bbodie52 wrote: :think: The information below explains vapor lock and how the mechanical fuel pump becomes "idle" when the carburetor float bowl needle and seat assemblies are closed. It also explains a fuel return system (similar in function to the turbocharged engine fuel filter return line) that was implemented to help cool the fuel in the fuel pump feed line from the gas tank to reduce the possibility of vapor lock when SMOG pumps and increasing engine heat associated with them became an issue...

The first portion of this video shows what happens in the fuel lines of a carburetor-based engine when the float bowl is full, and fuel flow through the lines slows or comes to a halt with heated lines and the engine running on a warm day — VAPOR LOCK! The remainder of the video discusses an in-tank electric fuel pump option and installation. The end of the video also has some good tips if retaining a mechanical pump is your chosen option.



The Corvair Fuel Pump Functional Operation

A careful examination of the fuel pump from the side would appear to show three gaskets that are sandwiched within the fuel pump body. These "gaskets" are really part of the flexible diaphragms that also serve as gaskets to seal the chambers of the pump. These diaphragms are made of a neoprene rubber material that has been reinforced with fabric to provide it with additional strength. The reinforced rubber diaphragms would be needed since the diaphragm must withstand the continuous motion and stress associated with the pumping action. Because of this it would not be possible to create a gasket using regular bulk gasket material to replace, for example, the lower pulsator diaphragm, because the pulsator diaphragm must have the necessary flexibility and strength to withstand the pumping action.

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The Pulsator Diaphragm is inside the pump fuel cavity. It creates an air pocket to minimize the pulsating of the fuel as it passes through the pump.
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As far as I can tell, the groove that radiates from the center cavity of the pump (pushrod area) is a vent of some type, but it only exposes crankcase pressure to the outside air. That groove appears to serve as a pressure relief. The pulsator diaphragm also serves to seal and isolate the vent groove from the adjacent chambers that would be exposed to fuel. That vent groove does not appear to be exposed to any portion of the pump body that would contain gasoline.
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The two valves shown in the illustration below are one-way valves. The inlet valve allows fuel to be drawn into the pump chamber from the gas tank. This occurs during the upward stroke of the pushrod. When the pushrod moves downward the spring at the top of the pump applies pressure to the main diaphragm to push the diaphragm downward, forcing the gasoline out through the other one-way valve towards the carburetors. This spring serves as a pressure regulator, to establish the 4-5 pounds of fuel pressure to drive the fuel into the carburetor float bowls.

If the carburetor float bowls are full, the floats apply pressure to the needle valve, which closes the valve and prevents additional fuel from entering the float bowl. This would create a "fuel fluid lock" that would prevent additional fuel from exiting the fuel pump chamber. When this condition exists the fuel pump return spring would be unable to push the diaphragm and pushrod pin downward toward the pushrod. Since the diaphragm would remain in the "up" position, subsequent upward strokes of the pushrod would not reach the diaphragm actuating pin, since the gasoline being held stationary in the chamber by the closed needle and seat assemblies in the carburetors would not permit the downward pressure of the spring to move the diaphragm into contact with the pushrod. As long as the carburetor float bowls are full, the fuel chamber in the fuel pump would also remain full and the diaphragm would remain in the upward position and would be isolated from the pushrod. This is essentially a neutral position that remains in effect as long as the carburetors are closed and cannot receive additional fuel. As soon as the carburetors drain enough to open the needle and seat assemblies, the fuel pump chamber would be drained as the spring forces gasoline through the one-way outlet valve. This would permit the diaphragm pin to once again come into contact with the pushrod, so that the next stroke would open the inlet valve and would draw additional fuel from the fuel tank. This new quantity of fuel in the pump chamber would be pressurized by the spring to be pushed in the direction of the carburetors to replenish the fuel supply in the carburetor float bowls.

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GM used two different methods to minimize vapor lock. Both methods provide a fuel return path to the fuel tank. The early method was only found in turbocharged Corvairs (because of additional expected engine compartment heat from the turbo system), and it offered a fuel filter that included a fuel return path to try to minimize the possibility of vapor lock, which can occur in a hot engine compartment — especially if the fuel is not moving within the lines (as with a full carburetor float bowl and a closed needle and seat, which prevents the fuel pump from moving any fuel until the carburetor uses some of the float bowl contents and again allows fuel to enter the carburetor from the fuel pump).

The second method added a fuel tank return line at the brass fuel pump outlet. This was added in 1968 and later engines when SMOG pumps and increasing engine compartment heat were introduced, along with a potential for vapor lock as stagnant, non-moving fuel quietly heated to a boiling point in the fuel lines while the mechanical fuel pump idled in a neutral condition caused by full float bowls (described above in the section The Corvair Fuel Pump Functional Operation.

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The fuel return line is one of those unique features of the last few model years, along with the SMOG pump plumbing and other unique engineering features GM invented to satisfy the SMOG police, California Air Resources Board, etc.

The fuel return line "Z" shown below was added during the final few years of Corvair production. This fuel line runs from a "cross" 4-way connector at the fuel pump outlet. This small diameter fuel line is more restrictive than the lines routed to the carburetors. It permits a small but continual flow of gasoline to return to the fuel tank. Without it the fuel pump goes into NEUTRAL whenever the float bowls are full and the needle/seat valves are closed. This stops the flow of gasoline until the engine consumes enough gasoline to restore the fuel flow back into the float bowls again. By adding the fuel return line, some gasoline is constantly flowing through the fuel pump feed line from the fuel tank and then back again through the return line. Keeping a constant flow of fuel moving uses the cool liquid to cool the steel fuel feed line "D" to help prevent vapor lock.

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:link: http://www.corvair.com/user-cgi/catalog ... IN&page=67
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There are other brands and models of 3-port fuel filters, that include a fuel return line to the fuel tank...
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3 port fuel filter


3 port fuel filter with 3/8" In Port - 3/8" Out Port - 1/4" By Pass and Vapor Port. Some Part Numbers to help you find one. This can be used with electric fuel pumps to keep the fuel cool in the engine compartment where temps can be 200 plus degrees.

Wix-33901 ACDelco-GF98 Powerflow-95041 Balwin-BF887 NAPA-3041 Hastings-GF20 Fram-G18 Motorcraft-FG12 Purolator-GF1118
These may need to be ordered as they are no longer a fast moving item in most stores. The 5/16" size is much more common.

Another option (instead of using a 3 port fuel pump) is a 3 port fuel filter after the pump. These were used on Large Engine GM Trucks, Ford Trucks and Jeep in their hot fuel packages. The small, or return port must be installed on top(or UP) so vapor is returned to the tank. Putting it on the bottom will trap vapor. Your Fuel Pump can handle this circulating flow very easy.

When you think about it, we really do not use very much fuel as we travel with our units. Therefore, there really is very little fuel flow through the fuel lines, basically stagnating and just sitting in the fuel line and pump. The fuel heats up at the pump and the lines leading to the pump near the engine. During this time, the fuel can vaporize and when it is in a gaseous state it simply pushes back and forth through the intake check valve of the fuel pump. The fuel pump cannot deliver sufficient fuel to the carburetor as required by the engine.

By keeping some fuel flowing through the fuel pump and low pressure fuel line, the temperature of the fuel pump, and fuel is significantly lowered and vaporization is avoided.
:link: http://www.gmcmhphotos.com/photos/3-por ... ilter.html

I believe either method could be adapted to any Corvair. A standard inlet/outlet 2-port filter could be substituted for the 3-port filter, but you would lose the vapor lock prevention feature. The 1968-1969 Corvair 4-way Tee brass fitting and an associated fuel tank return line could also be fitted, using parts like those shown on the Clark's Corvair Parts page. This would provide a more-positive, continuous fuel flow moving from the fuel tank and back again, which would create a liquid cooling system to keep the fuel lines feeding the pump cool.

Anther fuel filter possibility for your consideration... Corvairs often sit for long periods of time. Water accumulation in the fuel can become a problem.

Pure ethanol is hygroscopic; it attracts water, to the point that it will pull it out of the air.
Ethanol and gasoline will mix, but ethanol, gasoline and water will not; the ethanol-water mixture
will come out of solution and settle on the bottom of your tank.

This type of fuel filter can be useful to keep the Ethanol-based fuel in your tank from feeding water to the "Waterless Wonder from Willow Run". ::-):
FST Performance wrote:How often do I need to change the filter? (this is our #1 asked question)

This depends; how dirty is your fuel? You may be able to run several months on a spin-on/filter, then all of a sudden, it plugs up due to one batch of dirty fuel. This even happens with race fuels that have sat in tanks too long and collected water.
We recommend to change the fuel filter any time that you change your oil filter. Or, to get some type of time frame; every time you change the oil filter, remove the FST fuel filter and drain it into some type of clear container and let the fuel set; after a short time, look to see if there is any water (it will separate from the fuel)...if the "fuel" looks clear, then put a film of oil or grease on the filter seal and put it back on...if the fuel looks cloudy, change the filter.
:link: https://www.fstperformance.com/

:link: https://www.amazon.com/s/ref=nb_sb_noss ... tor+filter
There are many different designs, price ranges, filtration quality, etc. Do your homework on filter life, water drain capability, etc. Sounds like a good idea... especially with water separation capability from stale fuel and water absorbing modern gasolines.

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A standard coil is intended to operate on voltage that has been reduced by the ballast resistor wire in the wiring harness to approximately 7-8 VDC. This allows it to run cooler with less heat buildup in the in the internal coil. High performance coils are designed to operate at a full 12 VDC, which gives them a higher output voltage to the spark plugs.

It is not a bad idea to relocate the coil mount position. The standard installation of the ignition coil was always mounting it directly on the right cylinder head. The cylinder head on an air cooled engine gets very hot, and a significant portion of that heat can be transferred via the coil mounting bracket to the coil body itself. I would recommend relocating any coil as shown in the pictures below.

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Brad Bodie
Lake Chatuge, North Carolina
Image 1966 Corvair Corsa Convertible

caraholic4life
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Re: heating problems

Post by caraholic4life »

One thing you might want to verify, is that there have not been any obstructions to the air flow in, around, or between the cylinders.
If there is the slightest chance that mice have been able to get in and build nests while the car was parked, I would suggest looking in those areas. :my02:
1962 95 FC Van
1965 Monza Coupe
Mid Engine enthusiast &
Prior Kelmark Owner

64powerglide
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Re: heating problems

Post by 64powerglide »

Check the timing, if it's set to high it will quit when it heats up. Back when I was a young man I had a 58 Chevy 6 cylinder that quit running after a few miles, when it cooled off it would run again. At that time I didn't know much about engines, turned out the timing was to high. I was poor & didn't have a timing light. Finally got it set right & no more stalling. You still need to be sure you have those insulators on the carbs. :my02:
64Powerglide, Jeff Phillips

Kalamazoo, Mi..

dutchair
Posts: 64
Joined: Sun Apr 12, 2015 4:19 am

Re: heating problems

Post by dutchair »

thanks everyone for your input,

the isolators are installed,but is it possible that they are cracked or worn out ?I don't know how old they are ( maybe the original ones ?)

I also replaced the coil under the spare tire,but I have been told thatit does'nt make any difference,the problem is not a electrical thing but a fuel heating problem. the only thing that is possible is a wrong coil (a coil for a 4 cylinder instead of a 6 cylinder) I looked for it but there is nothing written on it. The only thing I can think of is that the original isolation mat under the deck lid isn't installed.but wasn't that installed to reduce engine noise ?

gr, dutchair

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bbodie52
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Re: heating problems

Post by bbodie52 »

:think: From my experience it is unusual to have a Corvair overheat like that, as long as the belt is intact and the fan is spinning. I've driven a 1965 140 hp four carburetor Corsa across country during the summer months with a car load of family (four people) and luggage and it never got over 400° — even when crossing the Texas, New Mexico, Arizona and Southern California desert during the daytime at about 70-80 mph. We drove from Atlanta to Los Angeles (about 2200 miles in three days) that way with only the family getting overheated... the Corvair did fine! Has the vehicle been sitting in a place where mice, squirrels, etc. might have found there way into the engine and possibly built nests on the head and cylinder barrels? This can happen — as shown below — and can prevent cooling air from flowing over the engine.
sooner wrote:...She started a few times when I got her, but overheated within a mile of driving...
Corvair engines seldom overheat like that as long as the fan belt is intact. However, if your engine has been sitting for a long time it may be suffering from a "critter invasion" with a lot of nest material packed under the sheet metal shroud. This blocks the air circulation around the cooling fins, and :angry: !

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Brad Bodie
Lake Chatuge, North Carolina
Image 1966 Corvair Corsa Convertible

dutchair
Posts: 64
Joined: Sun Apr 12, 2015 4:19 am

Re: heating problems

Post by dutchair »

thanks for your reply brad,but the engine has been outof the car,it was cleaned up and got new seals because the engine was leaking a lot of oil.

all wornout and missing seals has been replaced sothe cooling air can't escape and blowsaround the engine.

So I would'nt know what gives problems with the fuel. the carburateurs are getting very hot, but that iswat happens to all corvairs ? nothing has been modified everythingis orginalexcept for the fuel pump

steve57
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Re: heating problems

Post by steve57 »

Is the air outlet doors at the bottom of the engine opening properly. I don’t believe this was mentioned. If not hot air has no where to go.
Steve
Bakersfield,CA
1969 monza coupe
110, 4speed

dutchair
Posts: 64
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Re: heating problems

Post by dutchair »

Hi Steve57,

I Just driven the corvair for a few kilometers, and Ijust find out that the left door doesn't open properly.

I think that the connecting rod of the thermostat has come loose. I think it's best to fix the outlet door to make sure it does'nt close.
(maybe that will work to fix the vapor lock problem)

dutchair
Posts: 64
Joined: Sun Apr 12, 2015 4:19 am

Re: heating problems

Post by dutchair »

Hi Steve57,

I Just driven the corvair for a few kilometers, and Ijust find out that the left door doesn't open properly.

I think that the connecting rod of the thermostat has come loose. I think it's best to fix the outlet door to make sure it does'nt close.
(maybe that will work to fix the vapor lock problem)

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terribleted
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Re: heating problems

Post by terribleted »

If the door is closed while driving the left one would decrease air flow through the oil cooler and the left side of the engine for sure. Wire the door open and see if it fixes your issue. make sur the other side opens as well. These doors are really not critical in many climates. They help the engine reach operating temp faster is all. Cold winter weather, subfreezing temps yeah. but you will not hurt anything with them open.
Corvair guy since 1982. I have personally restored at least 20 Vairs, many of them restored ground up.
Currently working full time repairing Corvairs and restoring old cars.
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'stitch'
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Re: heating problems

Post by 'stitch' »

Also check where the fuel line enters the engine bay from the left rear tire well Is it laying right on the shroud? They get HOT! could almost boil the gas before it gets to the carbs. I spray painted a 1"x2" block of wood the same color as my shroud and wedged it under the line to keep it off the shroud. Is hardly noticable... :my02:

joelsplace
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Re: heating problems

Post by joelsplace »

A lot of the inlet lines do touch the shroud but they shouldn't unless they are bent.
114 Corvairs, 5 Ultravans and counting
Northlake, TX

steve57
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Re: heating problems

Post by steve57 »

Sounds like your thermostat on left door has failed and someone possibly screwed the swivel inward to keep the door closed to match the right side when cold. So warming up the engine opened right side and not left. Thermostat almost always fail to the open position. Let us know what you find.
Steve
Bakersfield,CA
1969 monza coupe
110, 4speed

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