1938 Plymouth

[Armandoalvarez]

1938 Plymouth flathead six cylinder exhaust manifold what years were they fit up to are they interchangeable are they close from a newer motor would it fit

[ply33]

Manifold gaskets are the same for 1933 through 1959 for cars and into the early 1970s for the equivalent industrial engines. They changed the carburetor mounting slightly over the years and they changed the throttle linkage too, so you might need to get an intake and exhaust set to have them both match.

 

There are two basic variations on the exhaust manifold, one with the dump at the back and the other with it between the #5 and #6 cylinders. Or maybe it is close to the #5 cylinder. The 1937 and earlier have the rear dump, I don't know about the 1938 but suspect it is the same as the 1937 and earlier.

 

I don't know about 1938, but the casting numbers matched between the 1937 exhaust manifold which replaced my original 1933 exhaust manifold. Well, almost matched, the is a dash number after the part number that was a bit higher and the date code was different. Those are not visible when mounted on the car.

 

And the Dodge L-6 cars used basically the same parts, at least in the 1930s.

 

Anyway, there should be a pretty big pool of available exhaust manifolds for you to pick from.

 

To keep your replacement manifold from cracking, don't over tighten the mounting nuts. If the manifold does not seal up with the correct torque then they are probably warped and a machine shop can flatten the surface for you. The early engines just used brass nuts but by the late 1930s they had a special washer and nut combination for the front and rear studs. The correct manifold fasteners are available, I think I got mine through Vintage Power Wagon.

Edited September 26, 2022 by ply33 (see edit history)

[keithb7]

The 1938 Plymouth came with a 23” long, 201 ci engine. 201,218 and 230 ci displacements were available in the 23” length block. 
 

Chrysler also produced a 25” long engine. It was available as a 218 and 226 ci engine in Canada 3 ⅜ bore. These were in the Canadian built Plymouths and Dodges only. They also offered the 237 ci, 251 ci and 265 ci options in Desotos and Chryslers in the USA and Canada. It had a 3 7/16 bore. 
 

You should be aware as many cars have had their engines replaced with non-factory optional engines for a specific model. For example my 1938 Plymouth had a 25” 226 engine in it when I bought it. I rebuilt it. Bored it over from 3 ⅜ to 3 7/16. Now it is a 237 ci. 
 

You may notice that the 23” block was offered in a 218. The 218 was also available with the 25” block. They are very different inside. Internal parts will not interchange.  Cranks, rods and bores are not the same. 
 

The 23” 201 crank is considerably smaller than the 25” long crank. Smaller bearing diameters as well. I have attached an image of the two cranks for comparison. 
 

If indeed you have a stock 1938 Plymouth engine you’ll want to be looking for manifolds and gaskets from any 23” long block.  Additionally, many trucks for many years had the 23” long engine. 
 

 

Edited September 26, 2022 by keithb7 (see edit history)