Runs great for thirty minutes then crappy. Don't know why.

[Mark8166]

Thought I had it fixed, went out for a ride today in my 65 Corsa 4 carb, it ran like a champ for 30 minutes, stopped at a store for a few minutes came out and it ran like crap all the way home. In the past few weeks I've put new plugs, plug wires, had all four carbs serviced, I just don't get it. Why does it run great cold but when warm, it stalls out at lights, runs like crap. What's wrong?

[UNSAFE]

Did it do this before the recent work ???

What do you mean by having "the carbs serviced" ???

It could be a choke problem - that is pretty easy to check with the air cleaner housing removed .

It sounds more like an ignition problem to me - two things that can act up when they get hot are the coil and the condenser .

The point gap or dwell should be checked when hot also .

Fuel pumps can fail also but a volume check when hot is pretty easy too.

Condensers are cheap - I'd just try a new one

[bbodie52]

Welcome to the Corvair Forum!

One other possibility comes to mind. You just "had all four carbs serviced". There is supposed to be a plastic insulator and a pair of gaskets (one above and one below the insulator) under each carburetor. Your problem sounds like it is possibly heat-related. Many carburetor rebuild kits come with only a single carburetor base gasket. Sometimes the old plastic insulators crack or disintegrate when removed and replacements would have to be ordered. Is it possible that the insulators were omitted after the carburetor rebuild? If so, with only a thin gasket and no insulator under each carburetor, this could cause excess heat to transfer from the hot cylinder heads to the carburetors and create a vapor lock problem. Your description of driving to the store and letting the car sit for a few minutes, and then finding that it ran poorly afterward could indicate a "heat soak" problem, where heat accumulates in the aluminum carburetors as it transfers from the hot aluminum cylinder head intake manifolds. This can overheat the gasoline in the float bowls and carburetor fuel passages and cause faulty carburetor operation in the overheated carburetors.

Question:
After driving my vehicle for a period of time, and after shutting off the engine I sometimes encounter a hard to start situation (engine cranks over several times before starting) and it usually occurs within a window of 15 minutes to one hour. What can I do to resolve this situation?

Answer:
Chances are you are experiencing heat soak, compounded by today’s blended fuels. Following are some things to keep in mind in an attempt to alleviate this situation.

Ensure that your fuel line is routed away from your exhaust and or block. This will help alleviate excessive fuel temperature in the supply line that can directly relate to pressure building in the line resulting in the needle and seat being overridden by the pressure causing a flooding condition.

Remember, heat rises and when the vehicle’s engine is turned off, the rising heat can easily penetrate the carburetor and cause the fuel in the float bowls to expand and eventually boil or percolate.

http://www.edelblog.com/tech-tips/resolving-heat-soak/

The insulator and gaskets are shown on the right in the following illustration, and in the Clark's Corvair Parts catalog page below...

Left-click on the image with your mouse to enlarge...

http://www.corvair.com/user-cgi/catalog ... IN&page=56


Part number C506: CARB BASE INSULATOR-THICK "PLASTIC" WE SUGGEST 2 "PAPER" GKTS (C506H) WITH THESE

Weight: 0 lbs 2 oz
Catalog Pages(s): 56(35),U,8(35)
Price:
1 - 3 $ 5.30
4 - 9 $ 5.05

[Mark8166]

Thanks guys for the info. I'll try the condenser and coil idea. The carbs were taken out gone over top to bottom cleaned and reinstalled. One carb was not working so it was replaced. As for the plastic spacers, all are present and in good shape. Thanks again for the help. I'll let you know how things work out.

[Jerry Whitt]

Two items mentioned in the other posts, the ignition coil and condenser are certainly possible, but are not likely.
The ignition coil can be tested. Your local AutoZone has the test equipment and if you find the right employee, will
test the coil for free.

You can test the condenser with visual inspection of the points first. The point tips should be clean. If there is a build up on either point tip,
the capacity of the condenser, measured in "microfarads" , would be suspect. There are some repair shops around that could test the condenser
which would take less than 5 minutes.

Another option would be to simply replace the condenser, should not be more than 2-3 dollars.

A more likely problem is something directly related to temperature. The choke plates are controlled by a temp sensor coil spring affair mounted on the
underside of the heads. When cool or cold, the sensor coil pushes a rod up that closes the choke plates on the two primary carburetors. When the
engine first starts, a round device on each primary carb, called a choke pulloff uses a vacuum signal to open the choke plates a little. As the engine warms
up, the sensor coil then changes shape, allowing the choke plates to open all the way. An idea to explore, are the choke plates actually opening all the
way when warm? They should be. To check, warm the engine to normal temp, pull the air cleaner assembly off so you can see the actual choke plates.
If they are wide open, good. If not, why not?