Unpredictable Operation

[61LaRk4dr]

Hello,

I am having problems getting my vehicle to where I can trust it on the road.

Year/Model: 1961 Lark 4dr. Sedan

Engine: ohv 6-cyl

Carburetor: Carter AS-2934-SA

Description:

When in Park, the vehicle will idle great, the exhaust is clear and the engine runs smooth. Once the car is put into drive the engine idle decreases to where when I barely tap on the gas, the engine sputters and then dies.

Now, if I allow the car to warm up for about 30 to 45 minutes, and then put it into drive I am able to press on the gas without any problems. Now correct me if I am wrong, but I didn't think a car had to warm up for that long before it could be driven.

I don't have a lot of experience with carburetors but I figure this is the best car to lern off of and it seems that I am now at a dead end seeking any information that might help me out.

Thank you

[gordr]

No, it should warm up a lot faster than that. First thing to check would be the heat riser valve, located in the manifold about 6" below the carb. You should see a shaft with a weight on it, and a "clock spring" behind the weight. That weight should be free to turn about 1/4 turn, and the spring should be strong enough (engine cold) to move the weight to the end of its travel.

As the engine warms up, the spring (bimetal strip, actually) relaxes, and allows the weight to drop, and opens the heat riser valve.

I'd guess that either the valve is stuck in the open position, or else the spring is gone or bent, and can't close the valve.

Another possibility is that the heat riser passages in the manifold are clogged with carbon, so that hot gases cannot reach the area below the carb where the heat needs to be applied.

Gord Richmond, within Weasel range of the Alberta Badlands

[Dick Steinkamp]

What Gord said, plus...the automatic choke might be inop or need adjusting.

[61LaRk4dr]

Thank you for your input, I noticed that the plate your refering to didn't turn easily but didn't think anything of it.

I will try that out, and thanks again.

[Roscomacaw]

Gord,
Your suggestions are good, however his car should be able to tackle cold/manifold driving from the start. Assuming the manifold's cold, the choke should be shut. If it's shut, the idle cam should elevate the idle until the manifold and the choke warm up and the choke opens. The accelerator pump might be marginal in it's function and not be doing enough when the car is cold (when richness is critical), but adequate once the engine's warmed up a bit.
My experience with these carbs is that over the years the linkage that works the accelerator pump gets worn and sloppy. This will allow a degree of throttle movement to go ahead without as assist from the pump - the result's a flat spot. A flat spot that's critical when the engine needs to see a rich mixture.
On the WW carbs, I've cured this slop by adding a finely would retraction spring across the doglegged rod that transfers motion from the throttle shaft arm to the accel. pump bellcrank. I can't recall how this single-barrel pump is actuated, but the slop might be eliminated in the manner I just told of.

Miscreant adrift in
the BerStuda Triangle


1957 Transtar 1/2ton
1960 Larkvertible V8
1958 Provincial wagon
1953 Commander coupe

[buddymander]

Ya, I bet Biggs is on the right track. But there's a way to check it. With the engine off, Look down inside the carb and then move the linkage slightly and see how much movement it takes to get a squirt of gas to be visible. You should see a squirt of gas with even the slightest movement.

[DEEPNHOCK]

As well as what was said (so far)...
Check for a vacuum leak..
Jeff[8D]

[r1lark]

quote:Originally posted by 61LaRk4dr

Hello,

I am having problems getting my vehicle to where I can trust it on the road.

Year/Model: 1961 Lark 4dr. Sedan

Engine: ohv 6-cyl

Carburetor: Carter AS-2934-SA

Description:

When in Park, the vehicle will idle great, the exhaust is clear and the engine runs smooth. Once the car is put into drive the engine idle decreases to where when I barely tap on the gas, the engine sputters and then dies.

Now, if I allow the car to warm up for about 30 to 45 minutes, and then put it into drive I am able to press on the gas without any problems. Now correct me if I am wrong, but I didn't think a car had to warm up for that long before it could be driven.

I don't have a lot of experience with carburetors but I figure this is the best car to lern off of and it seems that I am now at a dead end seeking any information that might help me out.

Thank you

Another possibility is that the tube that runs thru the exhaust manifold to heat the air going to the choke assembly may be rusted out. This will carbon up the automatic choke mechanism and make it operate poorly or not at all.

This tube was perforated on my 36K mile '64 OHV six. At that time, N&A had them and it was not too hard to change out.

Paul
Winston-Salem, NC

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