Intake Manifold Identification

[PT81PlymouthPickup]

Does anyone know what this NOS Mopar flat-head six manifold application might be?  I've been cleaning out my garage and found this in my collection of stuff, but can't remember where I got it. It definitely will fit the 23" block I have in my truck, but the center section where the carb sits is much taller than the one currently in my 39 Plymouth PT81 pickup. It's numbered 1120002-15. In the 36-40 Dodge truck parts manual the image looks like the taller one should be on my truck (TC equivalent Dodge). Perhaps the lower profile manifold was for car applications? Any knowledge or thoughts would be appreciated.

[9 foot box]

   I have that taller manifold for an engine going into a 47 WD21 that I’m working on. I like it for the higher flow and the disc at the bottom to atomize the gas better. I have one from another W series truck, without the disc. A S15 Desoto 251 that I have has the tall intake, as does the 49 Chrysler Spitfire in my 47 flatbed. I haven’t taken the carburetors off to see if there is a diffuser disc. The manifold is 47 and earlier in my opinion, and used on the one ton 230. The 251 engines had the taller intake port at least till 1952. The B series truck engines that I have, are short intake, like my cars. Your manifold appears to have the disc. I can only presume that atomizing the gas at the single port at the center of the block would be an improvement in performance or fuel efficiency and keeping the gas suspended in the intake manifold for the other cylinders to intake. 

[PT81PlymouthPickup]

On 8/2/2024 at 12:24 AM, 9 foot box said:

   I have that taller manifold for an engine going into a 47 WD21 that I’m working on. I like it for the higher flow and the disc at the bottom to atomize the gas better. I have one from another W series truck, without the disc. A S15 Desoto 251 that I have has the tall intake, as does the 49 Chrysler Spitfire in my 47 flatbed. I haven’t taken the carburetors off to see if there is a diffuser disc. The manifold is 47 and earlier in my opinion, and used on the one ton 230. The 251 engines had the taller intake port at least till 1952. The B series truck engines that I have, are short intake, like my cars. Your manifold appears to have the disc. I can only presume that atomizing the gas at the single port at the center of the block would be an improvement in performance or fuel efficiency and keeping the gas suspended in the intake manifold for the other cylinders to intake. 

Thanks for replying! Mine does not have the a disc you are referring to. My truck runs well as is with the shorter intake manifold, but I need to pull the exhaust manifold to replace a stripped stud. As long as I'll have it off I was contemplating using the NOS taller intake if it were the correct one for my truck or gave better performance. I'm thinking my 1939 Plymouth PT81  1/2 ton pickup originally would likely had the shorter manifold, but don't know how to verify? It has a 201 cu. in. engine. From past experiences, I've learned that sometimes leaving things alone if there are no problems might be a better plan? 

[greg g]

,y limited experience, when hood lines came down the casting below the carb got shorter.  At least in cars.  I have one from a 56, the chamber under the carb is inch deep, the one from my 46 is as deep as the one shown or a bit more, a 1954 I sold, split the differce.  If you look at the various after market dual intake they seem to all have eliminated that depth completely.   When I installed my Fenton, I put 1 inch thick phenolic spacers between carbs and manifold.  Without the spacers, my throttle linkage angles were wonky.  The truck linkage is different, so not familiar with how it hooks up.   As for performance who knows.  Seems the shorter distances between direction changes would flow better.  But on these engines it probably doesn't make much difference. With Chrysler  Corp being frugal as they were, I would imagine that the one that fit under the car hood in 54 also went in the trucks of that year or series.