The Stovebolt Site Forums The Shop Area Engine Shop Fast idle

Hi Stovebolters,
The automatic choke has started acting up this summer on our 1952 1/2 ton pickup. It has a 1956 235 car motor with the Rochester carburetor with an automatic choke. Has always worked excellent until this summer. Starts up well after depressing accelerator but idle only lowers slightly when I depress the accelerator following start up - stays on a much too fast idle. Once driven the idle lowers to a proper level within a quarter of a mile or so. Once the idle comes down it runs smoothly and idles properly from then on. Also starts quickly without the choke throughout the day. I do not notice any vacuum leaks, so I'm thinking adjustment or cleaning. Any advice would be appreciated.

May be a bit sticky. Try spraying the linkage with carb cleaner and work it good. Then spray again.

Thank you, Justhorsenround,
Will give that a try.
Chuck 52

Do you have the sheet metal stove apparatus on the exhaust manifold which provides the heat source for making the bi-metalic spring to open the choke plate at the correct time?

All these carburetors sucked up a bunch of schmutz through the tube leading to the exhaust manifold. If you take one apart, you'll see carbon (black) residue in the entire choke area. Spraying with carb cleaner will help a little. The best answer is to remove the carburetor and clean & polish the little piston (that is what stops working smoothly when it gets dirty). I've always wondered why nobody ever came up with a little filter to put between the carburetor and the exhaust manifold. Something you could replace every 10,000 miles or so would have stopped that problem for good.

Hello 52Carl and Jon,
I believe the tube from choke to manifold goes into the manifold without the sheet metal shield. I will check for sure tomorrow when I go to our storage garage and work on our truck. Will also remove the tube and make sure it is clear. Will get back with you tomorrow. Thank you, guys.
Chuck

The tube definitely has a heat shield that clamps to the exhaust manifold as 52carl says. Here is a picture of what it looks like.

I believe they called it a heat stove. It collects heat radiating from the manifold, where it can be drawn from the hole in the top of it.

Carl is correct.

The heat stove (and head tube/etc) for an automatic choke was first used on a small Chevrolet truck in 1954 (with the RPO Hydra-Matic transmission).

Operation is described on this page) - no illustration of the "stove", but it is referred-to.

Thanks to All.
Spraying the linkage, fast idle cam and set screw with carb cleaner seemed to do the trick. Started up fine and fast idle kick down with depressing the accelerator.
Chuck