Can you recommend a mechanic to help trouble shoot tune our new '64 Corvair Turbo in the Austin,Tx area?
The car had been running pretty smooth, but occasionally stalls and can be hard to start. There has been noticeable flooding out of the carb bowl (single barrel Carter going into turbo). It has an electric choke that seems to be working correctly. The choke butterfly is closed when cold and opens as it gets warm.
Friday we drove to next town and it ran perfectly smooth but stalled when we got there, was very hard to start and ran super rough all the way home. It would not idle, had to hand brake at stops to keep from dying. It was normal temprature (400 degrees). Choke was wide open.
The next morning I started it easy, choke on (closed), but when it got warm it stalled and died. Then flooded fuel out of bowl.
I am only guessing… but seem like carb is tuned to run cold with choke on and is either running terribly lean or rich once it is at temperature.
I think I threw my Corvair book away in 1976 when I sold it but sounds like you either have a major vacume leak or more likely a sticking needle valve for the float. Mine had two single carbs. A rich or lean setting would not cause fuel to flow out, only a stuck needle valve not allowing the float to raise and close off the supply of fuel. Might be time to just put a carb kit in it and clean it up good and go from there. Just my two cents worth.
400* !!! I would check the Radiator and water pump… LOL Just kidding…
When was the carb rebuilt, or has it ever been rebuilt?? If its never been done after 48 years its probably time… I would also join some of the Covair online forums as those are the guys who know these cars the best…
There’s an active owners group for these cars, I would join a club and find out who the real experts are, then ask them. That turbo was primitive by modern standards, and heat could be a real issue.
Any carburator is basically a controlled fuel leak. It’s a bowl of fuel, allowed as the gas is burned to stay full by the float dropping in the fluid and allowing a “needle valve” to open and allow the fuel line to refill the bowl.
The way you’re flooding fuel suggests to me that the float isn’t floating the way it should or the needle valve isn’t closing the way it should. My money is on the float. The stamped metal kind can develp leaks, the foam kind can break down and absorn fluid, and all of them can wear where the float “hinge” rotates in its holes as the float moves up & down.
Corvairs being an active subculture, alive and well, you may want to consider a replacement carb or a rebuild kit. With a Google you should have no problem finding either.
You need to get some shop manuals for this car, a Corvair owner’s group will be very helpful. I have trouble believing a turbo Corvair would have a single barrel carb? Perhaps a carb for one sides 3 cylinders and another for the other sides 3?
Whatever you are running rich and it isn’t the choke. That means a carb float that has cracked and filled with gas so it isn’t floating anymore, that would lead to too much gas. An improperly set float level (if the float is in fact OK) or several needle valves either miss set, or clogged by gunk and debris. A good carb rebuild may help but you’ll need a manual to reset the mixtures and idle speed on even a rebuilt carb.
Vapor lock…Today’s gasoline has very high vapor pressure compared to the gasoline sold in 1964…It is meant to be kept in a sealed fuel system under relatively high pressure. In an open system like yours, as soon as things heat up, the gasoline just boils in the float bowl and fuel lines and fuel pump. An electric pump installed up front near the tank should help. This may not be possible for you but small airports still sell 100 octane low-lead avgas which has very low vapor pressure (there is no propane or butane in it like car gas has) because the older aircraft can not tolerate any vapor-locking!!
You pump the avgas into 5-gallon cans labeled “off road use only”…
This is too cumbersome to be doing routinely. But if you try it and it cures the problem, then you know for sure what the problem is…if it IS vapor lock, THEN…
Install an electric push-pump up near the tank. Find a fuel filter with three ports, in, out and return…Run a return line back to the tank from that port. Now the fuel is circulating and staying much cooler. The last step is to insulate / isolate the carburetor from heat. Arrange a cold-air intake. These are the measures that were used to cure vapor-locking back in the day…
That’s along the line of my thinking, Caddyman. High under hood temperature may be boiling the fuel in the bowl. And although I am not very familiar with Corvairs it seems that 400* is awfully hot. When operating at that temperature the oil will flash off and become totally useless as a lubricant and the pistons will expand until they become tight in their bores. One of the Corvair forums would hopefully give some answers from experienced mechanics.
I had a Corvair Spyder a while back. Neat old car. It does indeed have a single barrel carb, pumped full of air by the turbo. I think 400° is below the red on the temp gage, and not out of the ordinary. This http://www.corvairforum.com/ is the forum I asked my Corvair questions to. They were very helpful, and know their 'Vairs.
Quoting @Caddyman "This may not be possible for you but small airports still sell 100 octane low-lead avgas which has very low vapor pressure (there is no propane or butane in it like car gas has) because the older aircraft can not tolerate any vapor-locking!! "
Do you know that many if not most older airplanes, like mine, have had Supplemental Type Certificates (STCs) issued to use regular unleaded car gas? Darned near every 80/87 octane airplane pilot I know, and know dozens and dozens, flys on mo-gas. See http://www.eaa.org/autofuel/
The Corvair doesn’t need 100LL avgas, although a 25% mix wouldn’t hurt most old cars that liked premium way back when. Finding someone willing to sell you some without the “road tax” may be a problem.
"The Corvair cylinder head temperature gauge is driven by a thermally vairable resistor called a “Thermistor”. It is screwed into the cylinder head below the engine. It is fragile, looks like a miniature spark plug. As the cylinder head temperature increases the resistance decreases. The gauge tends to be reliable, but the thermistors do vary with age. This is an old part design that is no longer made. A gauge indication of 400F at 10C ambient (50F) is not out of bounds, although on level ground at moderate speeds an indication of 350F is typical.
Do check to make sure the engine thermostat air doors are opening, although at cooler temperatures it’s common for one or both doors to stay partially closed."
My SWAG was shooting from the hip based on vague numbers from a lifetime of trying to pay attention and the Corvair experts are definitely the source on this problem as cylinder head temperature may far exceed engine temperature depending on where the thermistor is positioned. I did run across this information on VW air cooled engines regarding temperature.
It seemed in line with my recollections of engine temperature. My reason for investigating temperatures in air cooled engines in earlier years was from dealing with VW problems resulting from oil coolers becoming loaded with lint and dust which caused the oil to flash off and the driver side cylinders to overheat badly. A friend became a Porsche and VW fanatic while I leaned toward the UK.Also, I seem to recall driving a Corvair Monza and thought it had a 4bbl and turbo charger. But that was long, long ago.
@JosephEMeehan You are correct about the ignition system. It was certainly part of the problem I had with mine. The ignition coil is functioning in an area of MUCH higher temperatures than most coils will handle over time. I changed the coil, and the car ran again. I’m told the original Corvair coils were made for high temps. Unfortunately, where are you going to find an original high temp Corvair coil that hasn’t sat on a shelf for 40 or 50 years? Those would be of dubious worth due to age. I put a standard coil on it. It will probably be fine for quite a while.
I’d say if the carburetor is puking gasoline at time there’s a problem with the needle/seat and/or the float and vapor lock due to boiling gasoline is a very real possibility if the heat is spiking that high.
VW air cools have been known to roast themselves when the thermostatically controlled doors in the air shroud would not open for whatever reason. That’s why many of the old cools had the flaps removed or wired open.