Help with changing cub engine

Bucyrus · Postby **Bucyrus** » Mon Oct 25, 2004 7:34 am

Hello, first to cub forum, this is my first time, my question is I have a international cub lo-boy that the engine was bad in (the tractor is red and the seat is offset) the casting number on the orginal engine is 251341R7,I purchased a engine out of a cub (yellow) that had a casting number 251341R8 the one thing I noticed is the engine out of the yellow cub R8 does not have the bore for the brass clutch input shaft bushing.Can you tell me if the crank out of the R7 and the R8 are interchangeable or can the crank out of the R8 be bored for the bushing.And also is there any other problems that i will face between the 2 engines that will prevent the swap out to my tractor.

Thanks for any replys!

beaconlight · Postby **beaconlight** » Mon Oct 25, 2004 8:05 am

I don't know the answer to your question. I am trying to better understand it. Do you mean the pilot shaft bushing like on an old manual shift car? Never had a cub that far apart so I don't know if the bushing is in the crankshaft, the flywheel. or both
Can you get a look at the tranny on the cub you bought the engine from? Is it different than yours? Was the yellow one not a cub but a cub cadet. Does the fly wheel have a ring gear on the new one? I understand that the Cadet does not have a ring gear because it uses a combo starter generator combo that drives off of belts in the front of the engine.
Bill

Postby **John *.?-!.* cub owner** » Mon Oct 25, 2004 8:13 am

Beaconlight, I saw his post on another sight, and suspect Bucyrus may have an engine from a numbered low boy. Don't know about the pilot bushing hole, but they did have a completely different clutch arrangemant.

beaconlight · Postby **beaconlight** » Mon Oct 25, 2004 8:18 am

John Thank you.
Bill

Postby **George Willer** » Mon Oct 25, 2004 9:52 am

I'm doing the same thing as Bucyrus is. My 154 engine has the same part number and yes, the crankshaft does have the bore for the pilot bushing... but naturally, no bushing. I have no idea if or why his does not. I'm replacing a 251341-R1 with a 251341-R8

The 154 does not have a flywheel as such... just an adapter for a driveshaft. The driveshaft has pulleys to run belts to a jackshaft that has a clutch for the PTO. The driveshaft runs back to the main clutch which is located at the front of the transmission. This arrangement results in a live PTO.

Bucyrus · Postby **Bucyrus** » Mon Oct 25, 2004 1:02 pm

The pilot bushing is in the crank shaft of the orginal engine,not the flywheel. The tranny is different form mine .

Postby **George Willer** » Mon Oct 25, 2004 2:22 pm

Bucyrus wrote:The pilot bushing is in the crank shaft of the orginal engine,not the flywheel. The tranny is different form mine .

Yes, as I said in my earlier post. You will have to use the original flywheel, front pulley, manifold and exhaust, generator and bracket, and starter. I plan to use the 154 governor to retain tits' higher RPM and HP.

Naturally you will bolt the engine up to the current bell housing. Actually, the transmission itself is the same, except for the offset shifter and input shaft... just as even the Cub Cadets use the same transmission case.

Bucyrus · Postby **Bucyrus** » Tue Oct 26, 2004 8:18 am

What do you recommend to do about the R8 engine for a pilot bushing bore? Remove the crank and take to a machine shop and have bored?There is no bore in the end of the crank for it. Are the cranks interchangeable where i can use my original crank out of the R7 and put in the R8?

Thanks for any help

Postby **John *.?-!.* cub owner** » Tue Oct 26, 2004 9:02 am

It is strictly my personal opinion, nothing factual to base it on, but if you have a good machine shop nearby I would have them bore the crankshaft. Be a good idea to see if it needs turned and bearings replaced while it's out. May have to get the 2 jobs done at different shops. If you aren't familiar with removing the crankshaft pulley on a cub I suggest you search the archives for previous posts, I blieve there is also a procedure on Rudi's web site.

Bucyrus · Postby **Bucyrus** » Tue Oct 26, 2004 11:38 am

Yea, I think that is what i will do, I'd rather keep the orginal crank with the engine.

thanks for the help or any other help that someone can give

Postby **John *.?-!.* cub owner** » Tue Oct 26, 2004 8:49 pm

Further note, since you are going to take the crank to a machine shop anyway, just unbolt the front cover and take them together. They have presses and such that will make removing the pulley much easier than doing it by hand.

Bucyrus · Postby **Bucyrus** » Wed Oct 27, 2004 3:54 pm

I called several local machine shop none of which said they could drill the crank for the pilot bushing, so did some checking with calipers and calling found the only differents of the cranks is the late model crank has more radius on the rod journals than the early model and thats the reason for the narrow rod bearings on the late model than the early, So I'm going to see about installing the early model crank in the late model engine. I've been told by a engine rebuild shop that you can install the early crank in the late engine but not the other way (late to early). Can anyone give me the torque specs for the rod and main bearings.

Thanks for any help

Postby **Bigdog** » Wed Oct 27, 2004 4:32 pm

All you need to know is right here:

Specs

You may want to print this out.

Farmall Cub

Help with changing cub engine

Help with changing cub engine

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