Re: 1947 farmall cub- how do i get more hp

Sun Nov 11, 2012 10:14 pm

FWIW, I have a 51 and a 57 Cub with a Pennington 60" deck. I have 3 acres of grass that I mow and I have several small hills that I go up and down on while cutting grass. There is a part of my property that had some long grass that grew (about 12") and my 57 really struggled to the point of stalling. I lift the deck to get over it then cut it again dropping the deck a little lower. I have several Cub Cadets that I use also and my 169 with a 50" deck can cut long grass without a problem. I find that the Cub gives a better ride and is so smooth. So for me it all boils down to this, I like using my Cub for grass cutting and I have no issues with it doing what I needed. Underpowered, yes, but not incapable. If you have taller grass, a larger 14-16hp International Harvester Cub Cadet can handle it too, just more rough riding than the Farmall Cub. The cool thing about the Cub Cadets is that they are the little brother of the Cub, and they are built as well too.

Re: 1947 farmall cub- how do i get more hp

Sun Nov 11, 2012 10:51 pm


I don't think any one is comparing a '47 to a '75 and saying that they are equal. And you are probably correct. The early Cubs most definitely did not have the improvements later Cubs did. That stands to reason. And since there were only 5560 Long Stripes produced out of a total production of 253,184 Cubs over its lifetime, not all of us are going to be able to have that type of power or even get to experience it. So for the rest of us who are limited to 9, 10, 12 drawbar horsepower, then tune ups and getting our Cubs running at their peak is the best we can do. Not all of us either can afford to rebuild an engine which isn't cheap.

I do know that I do not even try to compare late production Cubs to the rest of em. They are not the same critter. IH had 30 years of development experience to improve the Cub, and if they hadn't the Cub would not have survived as long as it has nor achieved the production records it did. Simply makes sense.

It is like comparing McIntosh apples to Cortlands .. two very different varieties of the same apple.

Re: 1947 farmall cub- how do i get more hp

Mon Nov 12, 2012 4:29 pm

Upping the RPM won't do you any good unless you also reduce the drive pulley size on the PTO accordingly.

The Cub is already past its torque peak at 1800RPM. If you leave the pulley size ratio between the PTO and mower the same, all raising the RPM will do is gain you a couple of feet when the mower hits the grass. It will lug back down to where it ran before you increased the RPMs.

Didn't some guys do a bunch of dyno runs on various Cubs a couple years ago at a Cub Tug?

IIRC the difference wasn't all that earth-shattering from an early Cub to a 184 in REAL HP on the dyno. Certainly the 184 was nowhere near the 21HP that IH advertised it as having.

Many Cubs are tired, and aren't putting out even their factory rated 9HP. Overhauling the engine would make the most difference in that case.

Re: 1947 farmall cub- how do i get more hp

Tue Nov 13, 2012 11:05 am

Nebraska test 386 showed 9.23 belt hp and 8.3 drawbar hp in 1947.
It also showed a FLGS of 1600, so when you read down the table to 1724 rpm, the net belt hp is only 2.25. This shows the governor at work, cutting the fuel back and reducing horsepower above FLGS.

If one moves the FLGS up by 200 rpm, you will get the benefit of the HP increase between 1600 and 1800 rpm, which looks to be between 1 and 2 hp, but you will also get the benefit of being fully in the throttle and fully loaded by the time the load pulls the engine back to peak torque, which is around 1600 rpm. You will pull through more rough spots than you otherwise would.

I see this on the loboy ('65) vs the Fcub ('63 admitted it's tired), but the offset loboys had a higher no-load speed and thus higher FLGS than the Fcub of the same vintage.
The loboy labors less under load and recovers faster.

You should be able to turn up the no-load speed without changing any springs and since it doesn't have a mechanical fuel rack, you shouldn't need any other adjustments. This is governor math that I learned years ago at Cat....

Much of the difference between a long stripe cub and the rest of the fleet is just that - a much higher FLGS - up in the 2400 range, which significantly widened the power band. The bulk of the rest of the difference is due to the higher compression afforded by the domed pistons. Compression ratio=hp.
Last edited by ntrenn on Tue Nov 13, 2012 1:07 pm, edited 1 time in total.

Re: 1947 farmall cub- how do i get more hp

Tue Nov 13, 2012 12:53 pm

Don't forget the manifold. The larger carb also had a larger manifold on the Long Stripe.

Cam was changed in 1955. There was no cam change associated with domed pistons or any of the later mods. This is when RPM increased the first time.
Connecting rods. 1968
Domed pistons about 3 thousand tractors later. 1968
1975 brought the next changes.
Zenith carb
Larger manifold
cylinder head
RPM was bumped
351 891 Rl governor weights are listed for 154 and 185 Lo-Boys
374 710 R1 are listed for ALL Cubs in my parts books- both TC37 and ENG1

Any 154 engine has all the goodies.

Re: 1947 farmall cub- how do i get more hp

Tue Nov 13, 2012 3:23 pm

FLGS = Friendly Local Game Store?

Re: 1947 farmall cub- how do i get more hp

Tue Nov 13, 2012 5:50 pm

Matt Kirsch wrote:FLGS = Friendly Local Game Store?

My guess is Full Load Governed Speed.

Re: 1947 farmall cub- how do i get more hp

Tue Nov 13, 2012 6:17 pm

The bottom line to your question is that you can get about 5 more hp if you are willing to spend the money

Re: 1947 farmall cub- how do i get more hp

Tue Nov 13, 2012 6:21 pm

By the way I know of a cub or 2 that are turning around 2500 RPM or better and will pull like a scalded dog :D It all depends on what you do to them to change the power curve :wink:

Re: 1947 farmall cub- how do i get more hp

Tue Nov 13, 2012 6:52 pm

Getting the most out of your Cub requires a better-than-new engine in perfect tune, drive line with good bearings and bushing and a mower in the same great shape. Higher compression pistons, tight sealing valves and rings, pristine fuel system and proper installation/adjustment of the mower are the keys to peak performance. Electronic ignition has been shown to boost engine output by about 10% in a 184 in excellent mechanical condition.

When you find a pint-sized tractor that performs like a quart-sized tractor, it is unlikely to be 65 years old and powered by a small flathead engine.

Re: 1947 farmall cub- how do i get more hp

Tue Nov 13, 2012 7:02 pm

Nobody mentioned a wet/dry compression test. I would do that first, then a good tune-up and go from there. The compression check will let you know how close you are to rebuild time.

Re: 1947 farmall cub- how do i get more hp

Wed Nov 14, 2012 7:14 am

The subject is horsepower but I would like to say that mower design will also make a difference. I have never used a finish mower on my cub but do have an old Klipper on it. Tall grass used to be a problem until I took the rear skirt off the mower so that it could discharge the cut grass. I no longer cut half a swath.
The deck is not down to the skids and is not cutting where the grass has been run down. Wheelhorse used to build their lawn mowers to discharge this way which made back and forth mowing easier. I can do it with this. Vern