R how big can you make?

[sunnen]

Just wondering how many cube's can you get into a MM-R. Dont give me theories tell me the jugs to use, cranks that can swap how far can they be stroked which heads. I can do everything but stroke a crank.

 

[Molineone]

Sounds like a personal problem. Hahaha. (I know I'm not the only one thinking it...)

 

[Shawn W]

start with buying a 220 power unit or an engine out of a U302.
But then after you do any work to the engine, you wil bust the transmission gears out the top of the case after you get around 50 horsepower. and you get it in a hard pull. I know of 2 that have broke. maybe be better to start with a 335 or 445 or 4 star, if your looking at a small tractor.

 

[Augie]

Start with a 206B-4 crankcase out of a ZA or ZB. 3.8x6 is easy. There's room to swing more but it will take some work. You'll have difficulty finding blocks that will go much bigger than 3.875 and still be reliable. 75-80 horse is about it with the side-valve engine. The intake path is horribly constricted and is the ultimate limiting factor on hp potential. You can't make the same hp per cubic inch that you'll get out of an OHV engine.

My R puts out an honest 55hp at 540pto with a 48 head, 3.81 Jahn's pistons from Welters on a 5" 206B-4 crank, Scott Berry cam, basic gasket-match head work and points ignition, and does it on 97 octane E10 from the pump at Casey's. It has plenty to pull D2 type classes outdoors on 13.6x38 rubber up to 4500lbs outdoors in the summer. It's not even close at 3500lbs on cut 12.4x38's on indoor winter-time tracks.

I wouldn't worry about transmission or rear end strength if you're pulling a transfer sled at 4500lbs or less. Pulling deadweight, or stupid heavy, yeah you might break it.