[Deadhead]

66 4BBL AFB

I have been fiddling with this for a while. Need some help getting my choke set right.

Car runs totally fine in warmer weather. When it is cold it will fire right up (as long as all the gas has not evaporated out of the carb). But, when it gets going it wants to lope at idle and produces a lot of carbon and unburned gas out the pipes until it gets up to 120* or so.

If I boost the center idle screw on the carb, I idle too high once it is warmed up.

If I loosen up on the choke setting then it is hard to start but idles better.

I have the idle adjustment screw that goes to the fast idle cam on the side of the carb set so that it barely engages the cam.

What am I missing?

I figure I need to go at this when the car is cold and idling to solve the Prob., but I need to know which adjustment to start with since I am fine once the thing is above freezing.

Thanks for any help. I have been able to get this right on my other cars, but have not been able to dial up the right combo here.

[stevep]

Sounds like you have a choke unloading issue. Could be an internal vacuum issue or the internal choke linkage is binding.

[Engine-Ear]

Also, could the carb's original calibration (jet sizes, etc.) be conspiring against ethanol fuel ?

[Deadhead]

Originally Posted by Engine-Ear

Also, could the carb's original calibration (jet sizes, etc.) be conspiring against ethanol fuel ?

Actually the 93 octane I am currently running does not have any alcohol in it. I think the higher octane fuels have less or none. There was actually a breakdown on the pump I filled up at recently, showing reduction in % as octane rating went up. Was news to me.

Could be sticking. I will clean and lube the linkage & internals with ATF & see what happens. Vacuum should be good as all the tubes are new.

Thanks.

[Deadhead]

Took air cleaner off and messed with it while in the 40s outside. It could easily be binding. Lubed all linkage etc. and adjusted choke a little more. I think I have the cold climate or high altitude choke on this car. I have to have the choke dialed all the way to lean hash mark and then some for it to be set right.

I also see that it looks like my Acc. pump is leaking now. I hate pulling the whole perfectly adjusted carb top off to fix this. I have a new one with leather packing. I think I will try this over the rubber.

[carbking]

Lubing the choke linkage is a guarantee that it will stick!!! It should be clean, with NO lubrication.

The first thing to check would be the choke vacuum. There is a tiny passageway from the passenger side throttle bore that goes through the gasket to the choke housing, and ends behind the choke piston. A couple of backfires, or rich running can clog this passage with carbon, in which case the choke will not properly function.

To check remove the external choke tube from the choke housing. Start the engine. There should be a small vacuum on the portion of the choke housing exposed by removing the tube. If not, the carb comes apart for cleaning of the passage.

Adjustment of the choke AFTER you know the passage is clear:

(1) Wait until the ambient is between 65 and 70 degrees F, and the engine is cold. The choke cannot be properly adjusted at any other temperature.
(2) Loosen the three screws retaining the choke cover.
(3) With one hand, rotate and hold the throttle approximately half open.
(4) With your other hand, rotate the choke cover until the choke butterfly hangs open, then rotate slowly in the opposite direction until the choke butterfly touches closed with no tension.
(5) With your third hand , tighten the three retaining screws. The choke is now properly adjusted.

Jon.

[stevep]

Originally Posted by carbking

Lubing the choke linkage is a guarantee that it will stick!!! It should be clean, with NO lubrication.

The first thing to check would be the choke vacuum. There is a tiny passageway from the passenger side throttle bore that goes through the gasket to the choke housing, and ends behind the choke piston. A couple of backfires, or rich running can clog this passage with carbon, in which case the choke will not properly function.

To check remove the external choke tube from the choke housing. Start the engine. There should be a small vacuum on the portion of the choke housing exposed by removing the tube. If not, the carb comes apart for cleaning of the passage.

Adjustment of the choke AFTER you know the passage is clear:

(1) Wait until the ambient is between 65 and 70 degrees F, and the engine is cold. The choke cannot be properly adjusted at any other temperature.
(2) Loosen the three screws retaining the choke cover.
(3) With one hand, rotate and hold the throttle approximately half open.
(4) With your other hand, rotate the choke cover until the choke butterfly hangs open, then rotate slowly in the opposite direction until the choke butterfly touches closed with no tension.
(5) With your third hand , tighten the three retaining screws. The choke is now properly adjusted.

Jon.

That's great info Jon.

[carbking]

This article may offer additional information:

http://www.thecarburetorshop.com/Automaticchokes.htm

Jon.

[Deadhead]

This is excellent info. Thank you Jon. I will have to remove top to replace Acc. pump anyway, so I will go ahead & clean this passage.