Idle air vent

[my65]

On one of my carbs, I turned the mixture screw all the way in while the car was idling and it made NO difference to the rpm. I was told, by a carburetor rebuild company, that the idle air vent chamber must be blocked. He said it may clear up with carb cleaner or try to get a small wire thru it. I tried both these ideas this afternoon with no luck!! Does anyone have a way to clear it without dismantling the carburetor????

[bbodie52]

Just a thought…

You should confirm that there are no vacuum leaks in your system, prior to performing any tuneup settings with the carburetors.



You might want to check the idle speed synchronization between the two carburetors. It might be possible that your engine is idling on only one carburetor setting, possibly because the idle speed screw adjustments are not in sync.

If the idle speed screws are improperly adjusted, the engine may actually be idling based only on input from one carburetor. The fact that your idle mixture screw has no impact on the other side may be a symptom pointing to the lack of participation in establishing the idle speed by both carburetors.

If you have a UniSyn gauge, you can check the airflow through each carburetor with that. The carburetor synchronization procedures are discussed in the attached 1965 Corvair Chassis Shop Manual - SECTION 6 - ENGINE TUNE-UP, starting on page 6-5. If the idle speed screws have not been adjusted correctly — possibly with one carburetor adjusted to bring the idle speed up to a desired rpm setting, but using only half the engine to do it, a little tuneup synchronization work may be needed. The shop manual describes a procedure for using a strip of paper to determine the initial contact point when the idle speed screw first comes into contact with the carburetor throttle linkage. Once the initial contact point has been established, each idle speed screw is turned clockwise 1 1/2 turns to establish an initial idle speed setting that is identical for each carburetor. The initial setting for each idle mixture screw involves turning the screw all the way until it bottoms and then backing it out 1 1/2 turns. This is all accomplished with the main cross linkage temporarily disconnected from the carburetors to prevent it from possibly interfering with establishing the idle speed setting. Once you have verified that the idle speed setting on each carburetor has been matched with the opposite carburetor, the final idle speed and idle mixture settings can be determined to provide the desired idle speed. Any mechanical change in the idle speed screws setting on one side should be matched with an equivalent change on the other side, so that the carburetor idle speed settings remain in sync. A vacuum gauge or UniSyn gauge can be used to obtain a more precise synchronized airflow through the two primary carburetors. The final step involves reconnecting the cross linkage and adjusting the link on the left carburetor so that it slips into the cross linkage without impacting the idle synchronization (ensuring that both carburetors are open equally when the throttle is applied).

If the idle speed settings are in sync, but one carburetor does not respond to changes in the idle mixture screw setting, you may have to resort to dismantling the troubled carburetor to give it a good chemical bath in carburetor parts dip.

[my65]

Thank you Brad.
I went back and did just as you suggested and that confirmed my right primary carb is not supporting the engine at idle. The car would not idle until both screws were turned in almost to their max! Then backing out the right carb idle screw, nothing changed. I called the PO and he told me he put the rebuilt carbs on less than six months ago. I will talk to the rebuilder Monday to see if there is any warranty on it, if not, I guess I will get a kit from Clark or Rafee and do another rebuild on it?

[my65]

Well, I must say, Grant at Wolfe Enterprises stepped up to the plate and hit it out of the park! I called him on Monday and he said ship it to him. On Wednesday evening he called and told me there was soft white material clogging three out of four ports. He cleaned them out and would ship it back to me Thursday. Today I received it, install it with new gaskets and after a short time had the engine ideling at 600 rpm. Wow, it is amazing what running on ALL SIX cylinders will do!!