The Stovebolt Site Forums The Shop Area Engine Shop Autoline carb C-907

I have a 51 chevy 3100 that is new to me. I am trying to get the carb setup properly.
The motor is a 235 and has an autoline carb C-907 on it.

I have a few questions.
The throttle cable just hooked under the throttle linkage and looks a little odd. Is that how it is supposed to be hooked up?
The choke butterfly sticks wide open at the top of the adjustment. If I nudge the butterfly, the choke cable works as expected. There is a spring on the choke linkage, that doesn't seem to be doing anything.
Does anyone has a picture of a working carb linkage and throttle and choke cables hooked up or an original diagram?

Once I know how it's supposed to work, I can adjust it so I don't have to manually do it on each start.

Thanks,
JD

Hy JD1, it's hard to tell from the pictures, but I don't think the choke cam is installed correctly on the choke shaft. Is there a screw holding the choke cam to the choke shaft? If there is a screw, try removing it and see if you can turn the cam over and reinstall it so the piece with the spring tries to keep the choke open. Hope that helps.

I'll check for the screw tomorrow. I'll get a better picture of the choke linkage as well.
Thanks for the suggestion.

I had one of these set up correctly but sold it. If you can show a side image (showing the choke cam) I can tell you if it is correctly set.

Here is a side view of the choke. I pulled the choke cable tight and it's better, but the choke sticks wide open. If I want the choke to engage, I have to take off the air cleaner and nudge it down 1/8" (then the cable works fine).

The throttle cable is just bent under the linkage, that can't be right can it?

JD1, I put a cable stop installed below the throttle linkage; mine was bent around the linkage when I got it.

Can you post a link or pic of that stop?

That's a Rochester Model B carb. You need to know that when it's time to get a rebuild kit. Also lots of info on the 'net about the Rochester including some YouTube videos.

If you have the factory assembly manual, you can see how the throttle and choke cables are connected - see section 6, sheet 5.01. If you don't have the manual, you should get one. Amazon and parts suppliers have them e.g. https://www.amazon.com/1947-1954-Chevrolet-Factory-Assembly-Manual/dp/B00BGB7FXC

Step on the gas pedal and pull the choke knob out. The cable will turn the fast idle cam. The choke should close as there is a spring which makes the fast idle cam and choke move together. You can poke the choke plate with your finger and it should open and spring back afterwards.

Since you have to close the choke with your finger, either the spring is broken or not installed properly or there is something else hindering the smooth movement of the choke.

Thanks Gord, your comments helped. I ordered the assembly manual last week, and it just arrived yesterday.
I do have a couple questions about that diagram.
The screw 121749 listed on that page. Does that screw into the accelerator lever rod? The accelerator rod has a hole for the throttle cable, but not for a screw. Or is that a cable stop like YCGoat stated above?

I think the spring on the choke itself is broken. I see the one end of the choke spring but where does the other side rest against.

Thanks again for the help.

Here's what the spring should look like (and where you can get a new one if needed): https://www.carburetor-parts.com/Rochester-B-Fast-Idle-Lever-Spring_p_1124.html

If the spring is not broken, you have to wind it so it closes the choke.

The screw goes into the cable stop. The throttle cable slips thru the accelerator rod so you can press the gas pedal and override the throttle setting. BTW, I don't have the throttle cable. Don't see any good reason to have it.

Sorry for slow reply. I have both of the springs which were used on that model of carburetor. I also have the choke cam with the cable piece & screw. Image below. Send me a PM or contact me at [email protected] if you need them. They are not easy to locate today. I've attached another image showing how the spring connects to the cam on the back side of it. Note: if you need to replace the spring, you will need to remove the choke plate and the choke shaft. I also have the new screws and those are becoming harder to locate today. The lower spring can be replaced more easily.

By the way, Autoline's operation may have changed from the days when they were more highly regarded. When I was doing the Rochester study a year ago I wound up with one carburetor they had rebuilt in the last 6 or 7 years. It looked nice...clean and all. After I tried it and later disassembled it, the air horn was warped notably and their "fix" had been to use 2 gaskets. It didn't work (which was no surprise). Also, from what I learned, they now apparently use only a few numbers to identify all Rochester B and BC models: C-905 (auto choke-late version with center post for air cleaner), C-907 (manual choke) and C-906 (auto choke no center post for air cleaner). They do make them look nice, however. The one I had seeped gas constantly at the air horn/float bowl joint before I straightened it. It also ran horribly rich, but that was because the power piston was stuck. I don't blame Autoline for the power piston problem, however. It was as I said 6 or so years old when I got it. The float had not been set correctly however and that is just oversight or sloppy work.

Thanks Jon. That is the spring I am talking about and mine is definitely broken. I'll send you an email.
Thanks,
JD

Thanks again Gord for the information.