Engine stalling Air Cleaner fresh air flap?

[pickly]

I swapped out my stock Autolite carb on my 72 F100 with a 390 with a rebuilt one recently and i got it tuned up pretty good. While I was putting things back together I noticed that the previous owner had put a sheet metal screw in the side of the air cleaner that extended inside to basically hold the fresh air flap down. I think he did that because I don't think the flap opens freely like it's supposed to once the engine warms up.

Anyway, I took it out and the flap is released and is about 85% closed. I've been having a problem when driving through intersections or stop signs where i have to slow down or come to a stop. The engine sputters and then stalls. I have to remove the air cleaner and push the choke cam down to release the choke plate just enough to allow for air to pass through.

I'm wondering if the choke plate is being pulled down during low idle because of the air cleaner flap?

Any advice or experience with this type of problem?

[fordman]

how does it run without the air cleaner on it? i don't think the air cleaner has anything to do with your problem. but you might run it around the block without the cleaner and see how it works.

[FORDification]

The flap shouldn't affect idle performance being mostly closed, since that's when the engine needs the least amount of incoming air. If anything, a partially-closed flap would affect hi-rpm performance, by limiting the amount of incoming air. However, even that is still next to impossible, since you'd still be drawing in air from around the exhaust manifold...assuming the appropriate sheetmetal is still attached to the exhaust manifold and air filter assembly. No, the rough idle shouldn't be associated with an improperly-functioning flap.

What kind of choke do you have?

[pickly]

Thanks for the info.

I bought a replacement Holley rebuilt carb but when I got it in the mail it's the same Motorcraft that I took off (slightly different with the choke release in the back)

I think the model is an Autolite 2100 2bl. The carb that I took off had a manual choke and the previous owner removed the mechanisms on the choke and the choke plate that make it close. The manual choke is in the cab and was connected to the choke plate to move back and forth manually. (kind of like a lawnmower)

So, I put this one on and left the manual choke disconnected hoping that the choke mech on the new carb would work as planned.
The choke plate just seems to be closing down after about 10 mins of driving and then stalls. That's when I have to push the cam down a little to release the plate to give it some air.

[pickly]

how does it run without the air cleaner on it? i don't think the air cleaner has anything to do with your problem. but you might run it around the block without the cleaner and see how it works.

After it stalls and i push the choke plate down a little I've been leaving the air cleaner off and it seems to run normally. That's why I was suspecting the air cleaner preventing enough air getting to the carb.

I took the truck over to a shop where a mechanic tuned the carb up and claimed it was all good. Very frustrating. I changed the carb out because i was having a problem with cold starts and the engine taking forever to warm up and rev down. I'm in Minnesota where it's been a bit frosty so i was trying to limit some of my frustration trying to get to work.

[DuckRyder]

So, just so we are all on the same page:

Is the new carb a manual choke as well or a hot air assist choke, if it is hot air assist, is the tube hooked up?

[pickly]

Hi. the new carb is a hot air assist choke. The choke tubes are connected. The previous carb was also the same but the owner disconnected the choke linkages to the choke plate and had a manual cable in the cab.

I bought this truck in December and have sort of just been dealing with things weather permitting. Now that it's a little warmer I've started doing larger projects such as the carb. I'm thinking of doing the same thing and disconnecting the linkages to the choke plate and just having a manual.