1-1 The Stromberg 97 carb with vacuum port


Thought it was about time we wrote something on the almost mythical Stromberg 97 1-1 model. You don’t see many of them because they were never a stock OE fitment on any new Ford cars. Instead they were an aftermarket fit (to replace the Ford/Holley carburetor) for 1949 to ’53 Ford cars and small trucks with the infamous Load-o-matic distributor.

So how do we ID them, and why are they special? First off, note the writing on the side of the float bowl. By the time these came out, Stromberg had moved from South Bend, Indiana, to Elmira, NY. To the left of that, under where the kicker linkage goes, you will see a small 1-1 mark just above the circle with the 31/32 mark. The being a different bowl casting, the Stromberg part number – P-20671 – just above the 31/32, is changed from the P-21951 on regular 97s. In case you wondered, 31/32 is the size of the venturi in inches. 0.96875 inches, which is why it’s called the 97. There is another 1-1 mark under the bowl – check out the pictures.

While this example has the vacuum port, not all Elmira or 1-1 carbs have it. Most of these late model 97s also used this weird looking ‘W’ or ‘arrow head’ base. I have no idea why they changed to this ugly lower flange shape, but it’s interesting that many an aftermarket (i.e. 1950’s) intake manifold has the same shape mounting platform. Back then, you could buy 97s brand new, and this is what they came with, so I guess it makes sense.

Something else 1-1 carbs share is the ‘extra’ off-idle transition circuit. 97s were traditionally known for a slight off-idle hesitation. These two extra fuel circuits – you can see the small brass nozzles in the base/throttle body casting in the pictures – were the fix. They needed a brass jet because, by then, the throttle plate is moving away from the throttle bore wall and the exit for the fuel needed to be close to the edge of the plate to generate the correct local vacuum signal to pull the fuel out. That’s why the tips are angled to match the arc of the plate as it comes up. Eagle eyed readers will also notice that the plugs in the back of the base are extra large – needed because those little brass jets were inserted though those holes in the back of the casting into a seat on the opposite wall.

OK, let’s talk about the important part. As we said, the 1949-’53 Ford flatheads used the new Load-O-matic distributor, which, amongst its many failings, is the fact that it has no mechanical advance mechanism. It’s ALL vacuum controlled advance. So its compatible carburetor has to provide the right vacuum conditions all of the time. This is why a typical ‘ported vacuum’ carburetor like the Stromberg 9510A-VP, for example, cannot work with the Load-o-matic distributor.

The key to this carb’s compatibility with the Load-o-matic is the fact that it takes vacuum from two different places inside the venturi and throttle body. One is what you’d term the usual ‘ported vacuum’ position in the throttle body, just level with the transition ports, which is above the throttle plates at idle. The other is a small brass jet pressed into the bowl casting right at the narrowest venturi point. It had to be inserted from the outside, of course, hence the extra boss and lead plug on the outside of the bowl casting, just beneath the kicker linkage on the side. The fat extra boss on the side of the base is where you connect your distributor vacuum tube of course. The fact that the actual vacuum hole is tiny, almost hidden in the bottom of the huge fitting thread is indicative of the ‘hokeyness’ of the whole set-up.