The Stovebolt Site Forums The Shop Area Engine Shop How does the choke heat get there?

I am running a Rochester B with a choke thermostat on my 261, I added the thermostat from a 250 auto choke 'B' carb and I want it to work right. Inside the thermostat there is a little vacuum piston that hooks to the carb, and there is a fitting to connect to the heat source tubing. Where does the tubing attach to the exhaust manifold on a 235? Does it wrap around or just touch? I got everything else working right, the choke is fully closed at shop temperature and opens up when the housing is torch heated.

I want the auto choke so my wife doesn't have to worry about the choke when she drives the truck.

i just did the same with my 235. i pulled the carb off of some unidentifiable truck as it was only frame and running gear the wrecker was using as a yard vehicle. anyways...
the threaded outlet is a direct link to the exhaust manifold. the one i got has a tube that is inserted on the top side of the exhaust manifold btween the 1/2 and 3/4 outlets. i brought it home and had to drill my manifold to make it work. plumb it up on the carb side and it works great. i remember it took a while to set up though...
1 more thing; to keep the condensation from freezing up my choke after repeated starts, i drilled a small hole in the bottom of the pot metal choke casing . took me a few cold mornings full of swearing to figure it out. you will not have a vacuum leak as that piston has at least one if not two o-rings in there, which draw tight as soon as the engine starts for vacuum break

It is very easy to make a 'heat stove' to use when installing a hot air choke on a vehicle that did not have one originally.

(A) obtain a piece of sheet metal (.030 to .075 or so).
(B) cut into a rectangle 3 inch by 5 inch
(C) cut a half inch square from each corner
(D) fold up the sides and ends one half inch from the edges, forming a one half inch deep rectangular 'cup'
(E) drill a hole in the center for a vacuum fitting
(F) install a vacuum fitting in the hole, with the thread away from the 'cup'
(G) clamp the unit onto the exhaust manifold with the 'cup' facing the exhaust manifold. Muffler 'U-clamps' normally work well
(H) attach a quarter inch tube from the fitting to the heat input on the auto choke on the carburetor.

The air will be pulled into the 'cup' and warmed by the exhaust manifold, then pulled through the tube into the choke.

Jon.

Thanks, carbking, that's probably what I'll do. I hate to run real exhaust through the choke.

Don't make a hole in the manifold, carbon monoxide is deadly. A shortcut is to run the tube down to the manifold, ending at the manifold. But Carbking's method is far better. You could use brass, aluminum or stainless so the sheet doesn't rust away. If you use stainless sheet, be sure it's soft, some is too hard to drill through.