Installing and Tuning the Stromberg B No 3 Carburetor on your Model T Ford
When we left off the Stromberg B No 3 carburetor was rebuilt and ready for installation. The installation turned out to be easy. Tuning was another matter! Read on to see what we had to do to get a sweet running Model T again.
We install our fuel line and throttle control along with a choke rod. The gas was turned on. No leaks after five minutes! With the choke on and the ignition off, we pull the crank a couple times. Then we opened the choke and pulled another two quarter turns on the crank so that all four cylinders would hopefully be primed.
With the key on BAT and the throttle down a few notches, we pulled the crank upwards and were rewarded with an easy start! With the spark pulled down the key was switched to MAG. The engine was quite responsive but way too rich at less than 1/4 throttle. Hmmmmmm. Time to experiment with tuning.
With the float adjusted as low as it would go, we tried the spring tension adjustment on the automatic air valve. Loosening the adjusters would decrease spring tension, allowing the valve to open earlier. With the adjustments both set to full lean, the carburetor was acting a little better but was still way too rich, particularly at idle.
We tried a succession of springs on the automatic air valve, each weaker than the one preceding it. Over the course of two days and several hours of work, the car ran better each time a weaker spring was installed, but was still too rich at idle. We finally went to the local Ace hardware store and looked through their drawers filled with dozens of different springs. We bought two promising candidates ($1.50 each) and cut them to length for testing.
With the new spring installed and the engine running, the difference was dramatic. The engine now accelerates crisply. Idle is dead smooth. We got 15 free starts in a row before the engine stopped in a spot where the ignition was not firing. Now we just need to go for a test drive.
Out on the road, the car ran very well. Idle speed is quite low. The car has excellent response to throttle input. Cruising at low speeds or medium speeds is effortless. We went as fast as 40 MPH at one point to see how higher RPM’s would work. Very good manners at all road speeds.
We shut the car off and left it for a couple hours. Upon our return the throttle was opened about 1/4 of the way. The ignition was switched on. The car started on the first 1/4 turn of the crank. It has more torque at any speed compared to any of the Ford supplied carburetors.
The Stromberg B No 3 had been sitting on a shelf in the garage for years. I was a little bit afraid to put it on the car due to it’s complex appearance and unusual design. We won’t make that mistake again!