Correct choke setting on carb 4618S

[oldchevelle541]

Will be double checking my choke adjustment. Would appreciate feedback.
1) should butterfly be fully closed or slightly open at cold start.
2) where is a good fast idle setting in RPMs at cold start
3) when below freezing car will stall when put into drive or reverse. After it warms up there is no issue so I assume a chock adjustment may be needed.

Thanks in advance

 

[toolmanmike]

Will be double checking my choke adjustment. Would appreciate feedback.
1) should butterfly be fully closed or slightly open at cold start.
2) where is a good fast idle setting in RPMs at cold start
3) when below freezing car will stall when put into drive or reverse. After it warms up there is no issue so I assume a chock adjustment may be needed.

Thanks in advance

1) just closed.
2) there is probably a fast idle spec in the factory manual. I set mine by ear, probably 1000+ rpm on the highest step. If it's too low, it will stall, too high and the engine roars.
3) it sounds like you need some fine tuning. Let it run a bit longer to warm up. I usually let mine run 5 min. before taking off.

I don't use specs, I set mine by sight, sound, and how it acts from first start to drive away. You need choke to start and set the fast idle. It has to crack open when the engine runs to prevent flooding. Pay attention to the choke pull off there. Watch the choke coil open the butterfly as the engine warms. After it runs a couple min. or so on fast idle, you should be able to tap the gas pedal and it should drop to curb idle.

 

[Darter6]

fully closed

But not too tight. New York you deal with cold temps. Does the car sit outside or inside where the temps are warmer than outside?
I have found that I will have to set the choke twice with the spring/summer fall/winter.
So for winter temps right now adjust choke coil till butterfly is closed then 2 more notches on the housing.
Cold fast idle 15 to 1700 is where I like to be.

when below freezing car will stall when put into drive or reverse.

Headers ? no heat riser in manifold ? It will take a few minutes at fast idle, then curb idle for another minute before putting in gear.
All above works for me. Your results may vary. Good luck.

 

[Dragon Slayer]

Carter manual calls for 1700 RPM on Fast Idle setting hot motor. The fast idle setting requires the choke valve to be open 1/16". The vacuum pull off open 7/64". I would go to service manual and the carb section tells you how and what to set too.

 

[oldbee]

All the above are good but, it’s a fine balance that may take a few tries to get it right. Personally, if I can’t go into gear & drive away within 30secs I tweak a little more. I’ve owned mine for 58yrs and never worried about driving away with no waiting.

 

[toolmanmike]

All the above are good but, it’s a fine balance that may take a few tries to get it right. Personally, if I can’t go into gear & drive away within 30secs I tweak a little more. I’ve owned mine for 58yrs and never worried about driving away with no waiting.

I don't even do that with the fuel injected cars. I at least wait for them to idle down to curb idle.

 

[toolmanmike]

The reason I use a common sense approach to choke tuning is I think that 1700 rpm is too fast. That's half throttle for most stock engines.

 

[oldchevelle541]

Thanks everyone - yes super cold here now and car is always garaged but unheated. Sounds like everyone has to let theirs warm up and as these cars age they develop quirks that we have to re-learn things. For know when I touch pedal butterfly closes all the way before cranking. When warmed up its fully open. When we have a sunny day without high winds will play around with it. It is the original carb and I agree with having to adjust it more than once. I think I like the fast idle around 1200 to 1300 rpm for the 440 especially since its original. Carb is original to the car as well.

 

[Dragon Slayer]

Once started does the pull off open blade the 1/16"? If not, pull off can diaphragm can be bad. Easy to test with vacuum pump.

 

[toolmanmike]

Thanks everyone - yes super cold here now and car is always garaged but unheated. Sounds like everyone has to let theirs warm up and as these cars age they develop quirks that we have to re-learn things. For know when I touch pedal butterfly closes all the way before cranking. When warmed up its fully open. When we have a sunny day without high winds will play around with it. It is the original carb and I agree with having to adjust it more than once. I think I like the fast idle around 1200 to 1300 rpm for the 440 especially since its original. Carb is original to the car as well.

View attachment 1977060

Nice! It sounds like you are close. May be a little fine tune and a little longer warm up is the key. Another thing that effects cold drivability is the heat riser valve in the passenger exhaust manifold and the passages in the intake. When cold, the valve is closed to direct hot exhaust under the intake plenum to aid in cold engine running and faster warm up. Your valve may be stuck open or the passages partially blocked causing some issues. That can be a subject for another thread. You can fine tune to make up for issues there. Usually a longer warm up helps that situation.

 

[Some Car Guy]

My stock 69 440 seems to sit about 1700 and then races on up to 2500 or more after a minute as the heat builds. Lets me know to tap the gas and kick it off once it does that. I find it can still be a bit cold acting backing out and making the turn from garage. This is with a stock intake and heat riser in place.

 

[R413]

Super cold will need to run a bit to get heat in the intake and cylinders.

You don't want it to run perfect when it's super cold, because it will be too rich when it 38 degrees.

You don't want it rich and making black smoke it will ruin your engine over time.

I like post #2, spot on!

 

[oldchevelle541]

Once started does the pull off open blade the 1/16"? If not, pull off can diaphragm can be bad. Easy to test with vacuum pump.

its been too cold to try and start - waiting for a warmer day. I will say after I tapped the gas pedal and butterly fully closed I noticed a half hour later without starting it the butterfly opened to about 1/8" by itself. I thought that was interesting.

 

[oldchevelle541]

Nice! It sounds like you are close. May be a little fine tune and a little longer warm up is the key. Another thing that effects cold drivability is the heat riser valve in the passenger exhaust manifold and the passages in the intake. When cold, the valve is closed to direct hot exhaust under the intake plenum to aid in cold engine running and faster warm up. Your valve may be stuck open or the passages partially blocked causing some issues. That can be a subject for another thread. You can fine tune to make up for issues there. Usually a longer warm up helps that situation.

never thought of that but will check it out.

 

[oldchevelle541]

Super cold will need to run a bit to get heat in the intake and cylinders.

You don't want it to run perfect when it's super cold, because it will be too rich when it 38 degrees.

You don't want it rich and making black smoke it will ruin your engine over time.

I like post #2, spot on!

I will say a few days ago when we had a heat wave of 40-45 degrees she had a smooth idle without any hesitation.

 

[Darter6]

Carb is original

If you remove the choke rod housing you may find that the spring is adjustable. There will be a nut and striations + or - to increase or decrease spring tension.