1951 mercury carburetor choke adjustment

[Solo_909]

Hey guys,

So I finally got my 51 merc going but I think I messed up the choke. The carb has the black automatic choke on the side that you can turn either clockwise or counter clockwise. Anyone know how to set this properly?

Thanks,
George

[19Fordy]

Buy these manuals. It tells you how to adjust the choke in Chapter 12 of Volume 2. This is a good price. I'm not the seller.
https://www.ebay.com/itm/1949-1950-1...kAAOSwkLhaIK3n

[rotorwrench]

The cook stove spring will rotate the choke actuator shaft to pull the choke valve open as it warms up. The stove housing has graduations on it and the spring carrier has a tick mark on the body adjacent to the graduations on the housing. It is placed in the mid point on the graduations.

This is taking into account that the choke spring is properly engaged with the shaft lever and that the gasket for the choke stove assembly is in place and all is secure. The heat riser and the vacuum piston all have to be functional as well.

You can get a CD of the Lincoln Mercury O/H manual if you don't want a hard copy but you have to make sure it has the updates for your model year. I think 4/15/1951 was the last revision or at least it is in my original copy. I don't like the photo quality of the late reproduction hard copies.

The later 1951 cars with Merc-O-Matic and other wise have a divorced choke set up that functions directly off the intake manifold.

[Solo_909]

Originally Posted by 19Fordy

Buy these manuals. It tells you how to adjust the choke in Chapter 12 of Volume 2. This is a good price. I'm not the seller.
https://www.ebay.com/itm/1949-1950-1...kAAOSwkLhaIK3n

Thank you and I’ll do that however I need to fix this by this weekend to make it to good guys. Any tips?

[Solo_909]

Originally Posted by rotorwrench

The cook stove spring will rotate the choke actuator shaft to pull the choke valve open as it warms up. The stove housing has graduations on it and the spring carrier has a tick mark on the body adjacent to the graduations on the housing. It is placed in the mid point on the graduations.

This is taking into account that the choke spring is properly engaged with the shaft lever and that the gasket for the choke stove assembly is in place and all is secure. The heat riser and the vacuum piston all have to be functional as well.
.

Awesome thank you, so lthe carb was rebuilt but I twisted the the cap all the way to the right and left because I’m a moron and now need help with resetting it? So do I turn it all the way clockwise and then aline the mark or do I turn it all the way counter clockwise and aline the mark?

[WABOOM]

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I don't remember which way but you rotate it so it holds the choke closed (lightly closed) on a COMPLETELY cold engine and tighten it down there. That way when it starts to feel warm air rising up the intake it begins to open.

[rotorwrench]

The spring has tension in the choke on position when its cold out. You just make sure it engages the lever and install it in the relaxed state. Rotate it CW to the mid position on the housing and tighten it down. You don't rotate it any more than it takes to get it in the mid position. Heat and low pressure (vacuum) acting on the little piston is what makes the spring move toward the choke open position. The heat is drawn in by vacuum after the car starts.

You really need the Holley 885 information to see the photos. It may be on line somewhere but the Lincoln and Mercury application is outlined better in the factory overhaul manual. These carbs were also used on trucks but they had a manual choke and some had governors. The late 1951 carb is an 885 too but it has a completely different set up with the choke.

[WABOOM]

@scicala

[54vicky]

to repeat what rotor said make sure the tang on the spring is in the slot on arm if not you can turn left or right till you blue in the face.as already said a manual is a tool like no other.if not in the slot when turning you may feel the butterfly closing but if the spring is not in the slot all you have is the tang on spring pushing on arm rendering spring useless as it needs to be in the slot to function

[scicala]

You don't need to buy a manual unless you want to. Don't pay attention to the index lines cast onto the choke housing. In all those years the black choke thermostat cap (W/bimetal spring) probably isn't original anyway.
After sitting overnight with the car at aprox. 70 degrees temperature, rotate the black cap in the rich direction until the spring has just barely enough tension to hold the choke plate closed. If it's colder outside, adjust it with a slight tension holding it closed.


This is assuming everything in the choke is in good shape and not carboned up from a rotted out hot air tube in the intake manifold.


Sal

[rotorwrench]

Bi-metals can vary somewhat in tension so Sal's advice helps when conditions vary. Auto chokes were not perfect but eventually operators get used to the cold blooded tendency of these designs. When warmed up and in good condition, the 885 is as good as any carb for the OEM flathead V8 and they work well on the heavy Mercury cars.

The choke spring housings are pretty resilient considering they are heavy bakelite. Drop one on the floor and it will break so be careful with it. I've never broken one yet but I've found plenty of 885 carbs with broken ones.

[Solo_909]

Thanks fellas,

So here’s what I did. I waited till the motor was cool, I held the throttle quarter way open and opened the choke plate I then with the throttle quarter open turned the choke clockwise until the cops plate closed slightly and tightened it down there.

Now a couple more questions.
1. Does the choke linkage that the throttle idle screw rests on need to be in any locating when doing this?
2. Does the gas pedal linkage need to be installed a certain way so there’s not a lot of back pressure? Meaning if it’s too long will it keep the choke plate from opening when the motor is warmed up?

[Alaska Jim]

Do not adjust the choke housing with the throttle open. with the eng cold , open the throttle and then let it close all the way. this will usually make the choke come up on the high ide step .make sure the idle screw is on the high idle step on the linkage then with the air cleaner off ( so you can look into the carb. inlet ) turn the choke housing so that the choke plate just closes with minimal tension, then tighten the cover screws. this should be very close to the proper adjustment, and will work in warm and mild weather. you may have to adjust it a little tighter, or loser when the weather gets colder. I hope this makes sense. I know how to adjust the choke , but may not be clear in giving directions.----Jim ----- By the way I adjusted the 885 Holly on my 51Merc this way after I rebuilt the carb back in 1994, and have not touched it since. I am a retired mechanic by trade. try this link on you tube, it may help you.------ /www.youtube.com/watch?v=KS2E66Jtw-U

[Solo_909]

Originally Posted by Alaska Jim

Do not adjust the choke housing with the throttle open. with the eng cold , open the throttle and then let it close all the way. this will usually make the choke come up on the high ide step .make sure the idle screw is on the high idle step on the linkage then with the air cleaner off ( so you can look into the carb. inlet ) turn the choke housing so that the choke plate just closes with minimal tension, then tighten the cover screws. this should be very close to the proper adjustment, and will work in warm and mild weather. you may have to adjust it a little tighter, or loser when the weather gets colder. I hope this makes sense. I know how to adjust the choke , but may not be clear in giving directions.----Jim ----- By the way I adjusted the 885 Holly on my 51Merc this way after I rebuilt the carb back in 1994, and have not touched it since. I am a retired mechanic by trade. try this link on you tube, it may help you.------ /www.youtube.com/watch?v=KS2E66Jtw-U

Awesome thank you!

So I did what you said however ran into another issue I think. So I made the adjustments however the choke plate never opened up once it was warm. The choke plate didn’t even open when pushing the throttle in. If I losened the choke and allow the choke plate to open the car would die.

Any idea why that would happen?

[rotorwrench]

You will have to insure the heat riser system in the manifold is functional. The tube inside there can deteriorate or get carboned up and the riser tube to the carb can be corroded or damaged. The vacuum circuit from the base of the carb to the choke stove can get plugged. You can test the thermostatic (bi-metal) spring by heating it with a heat gun to see if it moves. The condition of the little vacuum piston in the cook stove and the linkage needs to be functional in all respects.

If any of these items are not functional then the system won't work as it should. I have two 1951 Mercury cars and have dug around for repair parts on more than a few occasions in order to keep them both functional. Many back yard mechanics were hard on the 885 series. Al lot of them are warped or damaged in some way by heavy handed treatment.

[Solo_909]

Originally Posted by rotorwrench

You will have to insure the heat riser system in the manifold is functional. The tube inside there can deteriorate or get carboned up and the riser tube to the carb can be corroded or damaged. The vacuum circuit from the base of the carb to the choke stove can get plugged. You can test the thermostatic (bi-metal) spring by heating it with a heat gun to see if it moves. The condition of the little vacuum piston in the cook stove and the linkage needs to be functional in all respects.

If any of these items are not functional then the system won't work as it should. I have two 1951 Mercury cars and have dug around for repair parts on more than a few occasions in order to keep them both functional. Many back yard mechanics were hard on the 885 series. Al lot of them are warped or damaged in some way by heavy handed treatment.

Okay cool I’ll check that tube later today when I get a chance.

Question, should the choke plate in the carb open up when pressing the throttle or is it different in the carb?

[rotorwrench]

The demand for air will overpower the thermo spring to a certain degree but it would still run rich if it doesn't open all the way.

[Solo_909]

A little update since is was finally warm enough to adjust. I made the proper adjustments as the directions above but I think I’m still having issues as I have stumbling when driving and pressing on the gas. It seems to clear if I kind of run it hard though. Any idea what may be causing that?

Also when I did the first step of the carb adjustment “pressing the gas peddle to the floor” the idle screw never came off the high carb step. It seems to just stay on the high step no matter of the carb is cold or warm.

The carb was rebuilt before installing in the car so do I need to adjust something else?

Thanks!

[Scotty's 52 F3]

I can't help you with your adjustments but, I just bought a Merc intake manifold so I can run a Rochester 2G.

Anyway, it came with the choke assembly if you need parts. I won't be using it.

[51 MERC-CT]

Originally Posted by Solo_909

A little update since is was finally warm enough to adjust. I made the proper adjustments as the directions above but I think I’m still having issues as I have stumbling when driving and pressing on the gas. It seems to clear if I kind of run it hard though. Any idea what may be causing that?

Also when I did the first step of the carb adjustment “pressing the gas peddle to the floor” the idle screw never came off the high carb step. It seems to just stay on the high step no matter of the carb is cold or warm.

The carb was rebuilt before installing in the car so do I need to adjust something else?

Thanks!

To check one source of "stumbling". The normal position for the accelerator pump adjustment is the center hole on the plate. If it is on the center hole move the pin to the outer hole or if in the inner hole move one hole outwards. (use a screwdriver to pry away and drop into hole)