Hot Air Choke

Reply Subscribe

Thread Tools

Search this Thread

Mar 18, 2009 | 08:43 AM

LARIAT 85

Thread Starter

Cargo Master

Joined: Dec 2004

Posts: 3,362

Likes: 22

From: Florence, SC

Hot Air Choke

I just picked up an Autolite 4100 4V carburetor to replace my Holley. My Holley used an electric choke, whereas the Autolite uses a "hot air choke." From doing research and asking around, I have come to the conclusion that hot air chokes are more efficient and reliable, and I would like to keep it. However, I am not sure how to install the 2 tubes.

There is a "hot air" tube that goes from the choke down to the manifold, and then another "fresh air" tube that supposed to hook up under the carb plate somehow, but then I do not know where the other end goes.

The next thing is I am now running long tube headers, and they do not have the "stove" needed to hook the "hot air" tube to. Is there a way to make this "hot air" choke work with headers?

Any help would be appreciated!

Mar 18, 2009 | 02:29 PM

fmc400

MSEE

Joined: Apr 2004

Posts: 10,386

Likes: 35

From: Austin, TX

Give this a read: https://www.ford-trucks.com/forums/8...ml#post6939116

I don't know if I agree with the statement that a hot-air choke is more "efficient." As a side note, electric chokes are easy to install because all it takes is a power source. Electric chokes are by far the most common setup with headers. The only real advantage hot-air chokes have is that they tend to follow your engine's temperature better, as they heat up based on exhaust temperature instead of an electric heater. Because of that, electric chokes can open up too fast in cold weather, etc. But if you set them right, you can usually avoid that problem. To install a hot-air choke, you'd need to fabricate a hot-air tube in the exhaust crossover. How this is done depends on your engine. What motor do you have?

Mar 18, 2009 | 09:07 PM

LARIAT 85

Thread Starter

Cargo Master

Joined: Dec 2004

Posts: 3,362

Likes: 22

From: Florence, SC

Wow, thanks a LOT, FMC400. That was very informative article on how a hot-air choke works. That cleared up most of my questions. I already have the insulated "hot air" tube with the flare fitting. What I don't have is the "fresh air" tube or the choke stove.

Quote:

To install a hot-air choke, you'd need to fabricate a hot-air tube in the exhaust crossover. How this is done depends on your engine. What motor do you have?

I have a 302 engine with an aluminum Edelbrock intake manifold and Thorley Tri-Y headers.

I would love to find out how to fabricate a hot-air choke stove so I can get this carburetor working properly!

Mar 18, 2009 | 10:34 PM

fmc400

MSEE

Joined: Apr 2004

Posts: 10,386

Likes: 35

From: Austin, TX

Check out the picture in this post:

https://www.ford-trucks.com/forums/8...ml#post7130920

That answers the "how" for the choke stove. This particular piece goes in the exhaust crossover on the intake manifold. Unfortunately, not all Edelbrock intakes have such a provision, so whether or not this is possible with your intake depends on which particular intake you have. If your new carburetor doesn't have a fitting for the fresh air intake tube, this could be done by installing a fitting on the bottom of your air cleaner. All that is needed for the fresh air tube is fresh air from the inside of the air filter.

If you don't have an exhaust crossover in your intake, an electric choke is pretty much your only option using your existing intake. To tell you the truth I can't think of many Edelbrock intakes for a 302 that would have one.

Mar 19, 2009 | 08:08 AM

dkf

Hotshot

Joined: Mar 2007

Posts: 10,101

Likes: 40

From: Pa

Another option is to convert the carb over to a manual choke. I got the "Help" kit and converted mine over.

BTW great article fmc400.

Mar 19, 2009 | 09:35 AM

LARIAT 85

Thread Starter

Cargo Master

Joined: Dec 2004

Posts: 3,362

Likes: 22

From: Florence, SC

What about running the "Hot air" tube down to the fire pipe someplace, and clamping it down to the pipe? I found this article from Pony carburetors about doing it this way...

Quote:

We like hot air chokes because the full opening of the choke plate corresponds with the time that it takes for an engine to reach operating temperature. When we receive requests for anything other than an automatic (hot air) choke, we often ask, “Why?” The answer is usually that the customer has removed the exhaust manifold and installed headers or HiPo exhaust manifolds. That is OK, you can still use an automatic choke. Instead of using the factory pre-bent stainless steel choke tubes that press into the exhaust manifold, we suggest using an extra long bendable insulated tube that clamps to the outside of the exhaust pipe. The open end of the tube will bring heated air up to the black choke cap in much the same way as the original tubes. You can bend this extra long choke tube to your specifications and it will look neat and factory installed. These tubes are available exclusively through Pony Carburetors.

However I wonder about leaving the "hot air" choke tube end open. Wouldn't that let dirt into the choke assembly? What about the "fresh air" tube?

Mar 19, 2009 | 12:49 PM

fmc400

MSEE

Joined: Apr 2004

Posts: 10,386

Likes: 35

From: Austin, TX

That's a creative idea. It's the same idea as the factory setup, however I can't vouch personally if it's effective or not because I haven't seen it done before. You're right that it will draw unfiltered air into the choke assembly, hence the purpose of the factory fresh air tube. Perhaps you could come up with a way to route the tube back up into the air cleaner to keep it a closed system; I'm not sure if that will decrease the effectiveness. If you try this, do post your results as I'd be interested to know how it turns out.

And thanks dkf!