MTFCA Forum

Received a nice original offset Master intake manifold for the Master Carburetor I found at Hershey. It’s clear the manifold is for model T by the two inlet openings and the clamp bosses. But … the throat opening is just slightly smaller than the carburetor throat opening. The difference looks like 3/32. A little file work would make the two fit.

Should I use this manifold or keep searching? What would be the result in performance by using a manifold with slightly smaller opening?

Mark, I suspect that you already know the answer to that...

In my opinion, taking a file to either would be like improving the Mona Lisa with a magic marker

BTW, I am certain that you'd never feel the difference before/after filing. You might detect a slight difference with emissions testing equipment, but not via the seat of your pants.

Take a look here for a lot of useful information: https://modeltfordfix.com/the-miller-ma ... el-t-ford/

Actually I don’t. I guess the question then is if it reduces the beneficial effect of that carburetor .. would it still be an improvement over a stock carburetor. Royce had a nice article on rebuilding and running one of these in his T. But I’m guessing it had the exact fit for carburetor to manifold.

The flange on this manifold also has an air valve installed and was slot cut to make removing / installing easier.

Is your reluctance to grinding the opening based on the rarity of the manifold? My assumption was that the transition from carb to manifold should be a smooth transition.

It would likely still be a huge improvement as-is, so long as the car can be started relatively easily.

efficient carburetion is a combination of a number of things, not just a minor sharp constriction ( the blending of which, will have minimal impact).

Airflow is dependent on the valve area and swept volume of the engine...it will not be modified to any sufficient degree that can be undone by simply blending the intake orifice. All you are looking for is for the fuel to remain atomized within the intake manifold and no blending will improve over what you have.

An example of the un-obvious is the manifold for the Zenith S4BF. The port area which mounts to the engine is suddenly and dramatically reduced to create a (second) venturi effect, which when removed by hapless hobbiests (seeking to improve air flow) vastly reduces the effectivity of the carb. Another example of unintended consequences, if you do an MTFCA search, is the frequent reduction in performance when "high flow" manifolds are installed without an increase in valve lift or diameter.

In carburetion, things don't always work out the way you expect. At the very least, I would try it as-is. You may find that the carb you have is in fact for a larger displacement engine and is hard starting (if the venturi is too large).

with respect to filing/blending, my personal view is that either part of your setup is quite rare and desirable on their own and it would be a shame to unnecessarily alter it without even being certain you 1. have a problem, or 2. that blending would solve an as-yet unmanifested problem.

the fact that the manifold is not matched to the carb size, but is from your description a match for a Model T, I very much suspect that while the carb may really perform, it might be hard starting and is likely for a larger motor...if that is the case, altering the manifold will not solve the problem.

Thanks Scott for this information. It’s clear that the slight opening increase suggests this carburetor was made for a larger engine. I’m amazed that around 1/16 would make such a difference. I guess I’ll try to install it as is and give it a try. May have to use smaller bolts with nuts rather than bolts that fit the threaded holes in the carburetor flange.

Hopefully everything will work out. At the very least, you have found yourself a true work of art and a rare one at that. They are exceptionally well made, were really expensive when new, and had remarkably advanced engineering for its time. It was the touch-stone of carbs of its day.

The 3/32 inch difference in less diameter of manifold is probably equal to the diameter of the carburetor barrel and should not be a problem. Make sure that the carburetor throat and manifold mount concentrate and not offset. This is probably why the one manifold mount hole was elongated for some other carburetor. I would not do any file work to the manifold.

That is one weird early carb if nothing else.

Has anyone ever seen one of them before?

yup........