Flathead engine question

[fireguyfire]

I have a question regarding flathead interchangability. The original flathead engine in my newly acquired 1940 1/2 ton is seized and hasn’t run in years. I’ve got the head off and am soaking the cylinders, however the bores look pitted as well as some of the valves, so I’m not optimistic that I will be able to bring it back to life.

I have a 58 and a 59 parts truck sitting in my pasture for a 58 Fargo  Sweptside I am restoring. Both have decent shape flathead engines in them.

I was told that any dodge flathead engine should bolt right in to my 40, and are interchangeable; I’m curious if this is true?

I would much prefer to run the factory correct engine, but if the flatheads do interchange, using one out of my parts truck would be a good plan B.

can anyone enlighten me on this subject?

 

The 40 is a Canadian dodge, and both parts trucks are Fargos, so my understanding is that as long as the cylinder heads are the same length you should be good to go.

[Young Ed]

Yes as long as both are the same length you should be good to go swapping the blocks. Use your original accessories. Only area you might run into trouble is the temp gauge holes got smaller by the late 50s

[Matt Wilson]

As far as I have been able to tell, the bolt patterns at the back of all the flathead sixes from around 1933 or 1934 through the end of production, some 35 - 40+ years later (for export during the last years) are the same.  As mentioned, the temp gage hole size did change at some point.  Also, some smaller engines used a flywheel with 4 bolts to connect to the crankshaft, but I couldn't tell you exactly which ones.  Someone else may chime in here.  I seem to recall reading about some engines that rotated in the opposite direction compared to most engines (most crankshafts rotate clockwise when viewed from the front - i.e., facing rearward to view the front of the engine), but I think these were pretty uncommon and weren't used in cars or trucks.  And of course, there is the length difference of about 2" (23" vs. 25"), which you already know about.  There were also manifold differences for updraft carburetors and exhaust manifold differences, and thermostat bypass differences, but these are relatively minor and can be accounted for without too much trouble.  Otherwise, I believe they are all pretty interchangeable.

[lostviking]

My 46 has the 230 from a 58 D100 (maybe it's a W100, CRS). The only difference is you need to use the flywheel from the 230. I'm not sure it you need the clutch and pressure plate also, but I've read the crank flanges are different thicknesses 218 to 230.

 

You didn't say, but I've also read that the Canadian trucks might come with the 25 inch motors. If so, ignore my post.

Edited December 4, 2021 by lostviking

[fireguyfire]

Will the 1940 3 speed bolt up to the later flathead?

[1949 Wraith]

On 12/4/2021 at 3:34 PM, fireguyfire said:

Will the 1940 3 speed bolt up to the later flathead?

You will use the bell housing and clutch from the 1940 Dodge, so there is no issue. The mid 50's bell housing mount on a frame cross member and are a different shape.