Choke thermostat on '71 455 q-jet

**Edit : the car is a '71... The carb and engine are '70**

I have been trying to get my automatic choke to work properly ever since I put the engine in the car several years ago. The Q-jet is a Cliff Ruggles rebuild, and I don't think there is anything wrong there. The carb works great.

Where I believe the problem resides, is the bi-metal t-stat that sits down inside the intake manifold. When cold, the tstat will properly set the choke. The problem is, as the car heats up, the bimetal tstat will allow the choke to open most of the way, but it doesnt pull down on the choke linkage. It kind of just goes limp. When hot, there is no resistance to movement in either direction. I took a video of it, while hot, seconds after shutting the motor off.

http://youtu.be/NMDhur4Wpq0

In this situation, I don't believe there is a problem with the exhaust crossover passages being blocked. I cold started the car with the tstat removed, and the well in the intake was too hot to touch within seconds.

Is there any way to adjust these tstats? Or would I just purchase a new one?

Thanks!!

 

OK, first, does the choke make the engine idle faster and run when cold? If so, that's half of it. With the motor running, the (aptly named) choke pull off will try to hold the choke blades open as long as there is vacuum. The choke coil doesn't really produce enough tension to pull the choke open. Check it once the motor is warmed up and running.

Here's how I remember it working from this diagram: Choke Linkage link

 

When the engine is cold, the choke coil pushes up on the linkage and sets the choke. It goes to high idle, and works down to normal idle in a few minutes as the engine warms. The issue is, the choke doesn't get pulled solidly in the open position. It will flop around a bit, and the secondaries remain locked out. I have a piece of wire holding the choke wide open. That's not a big deal in the summer, but with cooler temps coming in, it's hard to keep it running right for the first minute or 2.

 

There are several different locations on the choke arm on the side of the quadrajet, have you tried the other positions?

Those thermostats get old and do need replaced, so if you can't get it adjusted correct, I would suggest a replacement.

 

I was rummaging around my spare parts stash, and found another one on the other '70 intake I had. Put it on amd now the choke works fine..... However, I'd still like to find another. Does anyone know where to find these things? I've been scouring the different parts places on the web, and my local parts stores. So far I've turned up nothing.

I could swap to an electric choke, but they never seem to work as well as the factory style...

 

Electric choke conversion works well on the 75/75 hot air choke Buick quadrajets, but not on the divorced choke like you have. I am not sure who might have a replacement thermostat for you. Glad you found one that would work for now though.

 

Wow... I can't say how thrilled I am to finally have this working though.... Who needs FI when you have a well set up q-jet?! LOL. Cold starts and warms up beautifully now. Hoping though that the choke won't hurt my MPG too much. My average over the last 17 tanks of fuel is 12.3 MPG, in a mix of city and highway driving.