Manifold

Hi Mike, show us a photo of what you have, so we can see what might be missing.

The Series 81 intake is different from the earlier Series 80. The Series 81 is designed to create equal-length passageways for the fuel/air mixture to each cylinder. This creates a more equal mixture to each cylinder compared to a straight manifold.

But, the center port on the manifold is an exhaust port, used to heat the manifold, and the S81 design for this exhaust gasket is poorly designed. it leaks often and often the entire manifold gets replaced with a Series 80 version to eliminate the exhaust leak. More than half of the Series 81 engines I’ve seen have S80 intake manifolds on them.

The diagram you posted in your message is an excellent one, I don’t think there is a better one available.

Greg

Charles,

The intake manifold on my Series 80 is from a Series 81.

The temperature adjustment flapper on my exhaust manifold is frozen in the open position (at the 1:00 position) and really does not effect the functioning of the engine, as I don’t drive it in the winter.

It is used to increase the heat in the intake for cold weather.

I would not worry about it.

Someone probably removed it because it became frozen (rusted) in one position due to the water contained in the exhaust gases and the repeated heating cycles.

Greg’s comment about the intake manifold on Series 81 cars is interesting because the manifold

is aluminum and shouldn’t rust.

I had to have my exhaust manifold reworked because of all of the rust holes, but the Series 81 intake manifold was rock solid.

Peter

Here is Charles’s intake and exhaust manifolds. Note that both are cast iron. I have at least one if not more iron intake manifolds. The most common Series80 ones are aluminum. I’ve never seen a Series81 intake in any material other than aluminum.

I believe that the iron was used to make a much more robust and durable manifold. The Series 81 manifolds did have significant exhaust sealing problems on the center exhaust port for cylinders 3 snd 4.

Charles: I’d not bother replacing the exhaust deflector flap in the exhaust manifold. With today’s highly volatile gasoline, the overly heated intake manifold for the 1920’s fuel is no longer needed.

I’ll try to post a photo of a Series 81 manifold next.

Greg Long

Charles,

How about sending me an email with a photo / photos & description of what you have (parts) and what you want to construct?

Peter

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