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A C113 vs SC C123

M

mbrady.glide

Member
So I put new sleeves and pistons into my '39 A, which are the 3.125" bore of the Super C C123 engine. Looking through the parts catalog, the intake/exhaust manifold is the same for both engines, however the exhaust valves listed for a C123 are smaller; 1.16" vs the 1.22" sold for the C113.

My question is: based on the info found in the catalog, with my C113 now having the displacement of the C123, and assuming it theoretically has better exhaust flow, does it actually develop more horsepower than a factory C123, everything else being equal? Anybody dyno tested this combo? Any adverse effects on the rest of the drivetrain, under normal workloads?

I've got no experience with the C123 or Super C's so this is all speculation. Why would they have produced a larger displacement and then restricted its exhaust with smalle valves, considering the same manifold was used?
 
The 123 has a smaller combustion chamber and higher compression (especially compared to a distillate engine) the valve size on a
small engine at low speeds is not compromised very much with a small valve. Lift and duration may be different as well. Just
thoughts that may provide insight. Jim
 
As Jim said changes in the compression ratio...generally raising it...far outweighs any other changes to increase power in these old engines. Ya, increasing the bore size by an 1/8? can probably give a noticeable increase in power. If all was equal and you did have a dyno accurate enough to measure the difference, I think you would be hard pressed to see a difference in power produced by just testing the engine with one size valve then another with 0.06? larger valves. Especially at the relatively slow rpm they run. Just IMHO... So bolt her together crank her up and smile big as she is purring like a kitten. Never heard anyone say that about a 2 cyl. Deere now have you?
 

Believe me, I was smiling big when I cranked it over by hand and it fired right up!

I realize we're talking about a difference of less than 5 horsepower, just bench racing here. What I read on Tractor Data, said that both the C113 and C123 have the same compression ratio. If that's accurate, in theory I should have higher compression now with my engine with a 113 head, right? Smaller displacement necessitates a smaller combustion chamber if they have the same ratio. I'm calculating 6.5 to 1 compression now.

And yes, I much prefer the growl of an unmuffled 4 to that of a Jonnie popper twin. We just got my father in law a wide-front Deere B for Christmas, like what he learned to drive on.
 
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