Upping WD 28HP to 40 or 45?

The larger displacement comes from the 1/2 longer stoke of the 45 crank. All you need is a 45 crank and pistons. A lot of the rebuild kits have a 4 1/8 bore too.
 
A legit WD engine on gasoline made 34 HP at the PTO. A legit WD45 engine on gas made 43 HP. Compression ratio raised from 5.5 to 1 to 6.5 to 1. Compression test on a WD was 100 psi. A WD45 was 125 psi. Larger carburetor, air cleaner and better intake/exhaust manifold. Tall cylinder head was used on the last year or so of WD's and all WD45's and has zero performance gain. It has better coolant flow is the reason they changed it. Both engines were 4 inch bore. The WD45 got 1/2" more stroke at 4 1/2". After market 4 1/8 pistons are fine AS LONG AS THE COMPRESSION RATIO is the same or higher. Often, they aren't as high, especially when they are used in a D-17 engine. What you want to do is very easy. Just have to decide which way to go to get there. Camshaft change isn't needed as they are the same grind.
 
You'll also want the WD45 air cleaner and carb to flow enough air. I'm not sure about swapping the original WD manifold for the later 45 one. It'd help just to get the carb lined up with the air cleaner is you swap to the taller head.
AaronSEIA
 
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Pistons, Crank, Manifold.

Dealer marketing video from back then
https://www.youtube.com/watch?v=cYH3q9nJ-fc


I just updated the manifold on my WD to the WD45 style. I had to remove the original manifold to fix some gaps/bushing seals as I was getting blow-by and poor performance. I decided since I had to fight with rusty bolts to get the manifold off, why not put the updated manifold on it at the same time (and a new muffler) and perhaps improve power. I didn't do any 'dyno' testing before/after.
Radiator fan made the mic warble, but here's before/after:

https://www.youtube.com/watch?v=altySE5s2G0



Example discussion/testing of what manifolds can do ... does the WD45 manifold put on a WD improve performance much? Possible, if it's magical.
https://www.youtube.com/watch?v=EX0oamHHUTw

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The manifold itself, still using a smaller WD carb and air cleaner, probably little to no difference. It took the A-C engineers five things to gain the extra 9 HP. Compression increase.....25 more cubic inches (crankshaft stroke).......manifold improvement........larger carb.....larger air cleaner. Anything you don't do will not get you what they got. M & W used to make an overbore (4 1/8") piston kit that was I think 7.0 to 1 compression with 212 cubic inches. They claimed 40 HP from 34 HP. My Dad/Granddad had one and it was never the tractor our WD45 was.
 
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...The carb upsize may not be necessary as there's this guy who put a lawn mower carburetor on his V-8 engine.

Initially he did it for fun, to be a conversation piece, for youtube views, and for 'all you guys who were so rude on the different Facebook groups'; but he had success that surprised himself. A lawn mower carburetor runs his V-8 to 70mph on the freeway and achieves better fuel economy on his long daily commutes.

https://www.youtube.com/watch?v=FwhMz2kR4pw


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Ask the 3500 lb puller guys , what machine shop they use , they do pretty good in the class should be able to get a hundred plus out of it
easy.
 
(quoted from post at 16:07:41 05/15/22) Ask the 3500 lb puller guys , what machine shop they use , they do pretty good in the class should be able to get a hundred plus out of it
easy.
I've built a dozen or more engines like that. I'm under the assumption this man wants to farm with this tractor and use REGULAR gasoline, not racing gas. So, with the WD45 crankshaft and 8.0 to 1 compression pistons from a One-Seventy engine, you'll make about 53 to 55 HP at the PTO at 1400 loaded engine RPM on regular gas. This must include the carb, air cleaner, and manifold from a WD-45. You want 100 HP ?? It will take many more cubic inches and much higher compression that requires 112 octane fuel. You cannot farm with it.
 
A-C didn't do that until after the compression was 8.2 to 1 and after a larger than a D-17/WD45 carb was used. Will it hurt ?? Nope, but the HP gain won't be as great as doing the other things first.
 
Our WD has M&Ws in it and it is 38-40 HP
on most dynos. They wake up a WD but as
you said it isn't a 45 by no means.
 
I always said, you got the loaded wagon rolling in third gear with the WD and then shifted into road gear. The WD45 would just take off in road gear with the loaded wagon !!
 

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