On second thought...

The other day I thought I wanted to trade my Ford 641 to a little more modern tractor. After looking around, I decided that mine was probably just as powerful, and probably in better shape than most of the ones I looked at. I've found a rebuilt steering box for $150, and I'm getting some new rear rims, and getting around to fixing a few things that I had let go. After that I'm going to slap a new coat of paint and some decals on it.

Now to my question. A few years ago I ordered a 3.5" overbore engine kit from here and installed it on my tractor. I believe this is just a little bigger than stock at 3 7/16". TractorData lists the stock 641 at 48.4 hp. Does anyone know if the upgrade makes any appreciable difference in horsepower?
 
Tractor data is way off those are numbers for a 841 not a 641. As per Neb test the 641 HP is 33.60HP. As for much increase you may get 1 or 2 more HP with the over bore
 
(quoted from post at 11:40:07 09/30/14) Tractor data is way off those are numbers for a 841 not a 641. As per Neb test the 641 HP is 33.60HP. As for much increase you may get 1 or 2 more HP with the over bore

Thanks, I didn't think it could be much of an increase.

I looked those Neb Test numbers up earlier. That hp is for the PTO. TractorData lists the PTO at 32 HP. Pretty much the same. From what I can find, the engine HP of a 641 is 48 and a 841 is 63. Can anyone verify if this info is accurate?
 
(quoted from post at 15:03:51 09/30/14)
(quoted from post at 11:40:07 09/30/14) Tractor data is way off those are numbers for a 841 not a 641. As per Neb test the 641 HP is 33.60HP. As for much increase you may get 1 or 2 more HP with the over bore

Thanks, I didn't think it could be much of an increase.

I looked those Neb Test numbers up earlier. That hp is for the PTO. TractorData lists the PTO at 32 HP. Pretty much the same. From what I can find, the engine HP of a 641 is 48 and a 841 is 63. Can anyone verify if this info is accurate?
can't verify any of those numbers, but can sure discredit them! The "test of reason-ability" (some call it the 'smell test') tells me that 1/3 of the horsepower is NOT going to be lost in passing through a single reduction gear (48 down to 32).
 
The overbore kit is likely good for about 3 HP max.

The late model 134 CI engine produces about 34 HP at the PTO at rated speed.

A decent late model 172 CI engine will produce about 10 PTO HP more than your 134 CI even with the overbore kit.

Dean
 
They are all right with that HP, cuz its Engine HP! PTO tested HP was 31.78. Engine HP on an 841 was 62.6. Belt tested HP was 44.71
HTH, Dave
 
(quoted from post at 16:12:36 09/30/14) They are all right with that HP, cuz its Engine HP! PTO tested HP was 31.78. Engine HP on an 841 was 62.6. Belt tested HP was 44.71
HTH, Dave

So how come a 4 cylinder 4000, which was the same basic engine as the 801 series, produces only 42 or 44 PTO hp when the 3 cylinder 4000 produces 52? According to all of the references, they are both supposed to have around 62 engine hp.

If they really do both produce 62 engine hp, where's the extra 10 hp getting lost on it's way to the PTO on the 4 cylinders? The 3 cylinder's all had independent PTO, so they should be losing just a hair more between the flywheel and the PTO than the 4 cylinder models which all had trans or live PTO (except for the S-O-S models of course).

I would bet that the 4 cylinder 172 never produced any more than about 54 hp at the flywheel given the measured PTO numbers from the Nebraska tests.
 
(quoted from post at 17:06:55 09/30/14)
(quoted from post at 16:12:36 09/30/14) They are all right with that HP, cuz its Engine HP! PTO tested HP was 31.78. Engine HP on an 841 was 62.6. Belt tested HP was 44.71
HTH, Dave

So how come a 4 cylinder 4000, which was the same basic engine as the 801 series, produces only 42 or 44 PTO hp when the 3 cylinder 4000 produces 52? According to all of the references, they are both supposed to have around 62 engine hp.

If they really do both produce 62 engine hp, where's the extra 10 hp getting lost on it's way to the PTO on the 4 cylinders? The 3 cylinder's all had independent PTO, so they should be losing just a hair more between the flywheel and the PTO than the 4 cylinder models which all had trans or live PTO (except for the S-O-S models of course).

I would bet that the 4 cylinder 172 never produced any more than about 54 hp at the flywheel given the measured PTO numbers from the Nebraska tests.
ithout hard proof, I'm sticking with my story that you don't lose 16 out of 48 horsepower via a single 2.75 :1 gear reduction.
 
Okay fellas, I'm sorry I opened up this "can of worms"! My sincere apologies!
We all know that Tractor Data never puts out false info! Tongue in cheek here!
My only point, in the beginning, was that the original poster was quoting engine HP, not PTO HP!
Dave
 
(quoted from post at 18:00:09 09/30/14) Okay fellas, I'm sorry I opened up this "can of worms"! My sincere apologies!
We all know that Tractor Data never puts out false info! Tongue in cheek here!
My only point, in the beginning, was that the original poster was quoting engine HP, not PTO HP!
Dave
will go along with, "he was quoting 'something', but not PTO HP. I'll accept 2 to 3% loss in those gears & if really pushed maybe 5%, but SURE NOT 33%!!
 
I agree the numbers don't match up.

However, engine hp is likely in a stand, no power steering,
might not be a fan or generator.... Hook up the drive shaft to a
dyno, and nothing else, run it as hard as you can for a minute
or two and see what the raw engine tops out at.

Sort of like the air compressors rated at 2-6 hp, but have a
120v motor on them. It's not a real world thing.....

Pto hp is closer to the real world, a full tractor running.

Paul
 
(quoted from post at 08:29:26 10/02/14) I agree the numbers don't match up.

However, engine hp is likely in a stand, no power steering,
might not be a fan or generator.... Hook up the drive shaft to a
dyno, and nothing else, run it as hard as you can for a minute
or two and see what the raw engine tops out at.

Sort of like the air compressors rated at 2-6 hp, but have a
120v motor on them. It's not a real world thing.....

Pto hp is closer to the real world, a full tractor running.

Paul

I agree, plus also there's the "horsepower advertising wars" factor. Back in the day manufacturers would advertise engine horsepower that might not be accurate just to make a claim against the competition. Saw it recently in lawn and garden tractors from the late '90's through around 2006 or 2007 when a class action law suit was filed against all of them by some consumer group. Since then they are a lot more conservative if they even advertise hp at all. Lots of times you'll see the displacement in cc advertised with no hp number listed.
 
(quoted from post at 07:29:26 10/02/14) I agree the numbers don't match up.

However, engine hp is likely in a stand, no power steering,
might not be a fan or generator.... Hook up the drive shaft to a
dyno, and nothing else, run it as hard as you can for a minute
or two and see what the raw engine tops out at.

Sort of like the air compressors rated at 2-6 hp, but have a
120v motor on them. It's not a real world thing.....

Pto hp is closer to the real world, a full tractor running.

Paul

Dont forget the hydraulic pump, power steering pump, water pump, fan, distributor, all taking up hp off the engine. The hydraulic pump alone can take 5 hp off the engine very easily. 2.5 for the power steering, 1 hp for the water pump and fan. then throw in the flywheel, transmission loss, and pretty soon you start to add up.

That is why the state of Nebraska had passed a law about all tractors had to be tested to be sold in that state. IE the nebraska state university conducted all the tests and that became the world wide standard for many years.

I always go by pto hp, but the new tractors today are going back to engine hp,, not a very useful figure.
 
I think we all agree that its the PTO HP and Drawbar HP that actually do the work on a tractor; not necessarily the engine HP. With that said, am I somewhat correct in saying that if the overbore kit adds about 3 horsepower to the engine, then I might possibly get about +1 1/2 to +2 HP on the drawbar and PTO?

I know that its probably a negligible amount, but I was just wondering. I've never seen any published data anywhere on overbore kits.
 
(quoted from post at 13:57:34 10/02/14) I think we all agree that its the PTO HP and Drawbar HP that actually do the work on a tractor; not necessarily the engine HP. With that said, am I somewhat correct in saying that if the overbore kit adds about 3 horsepower to the engine, then I might possibly get about +1 1/2 to +2 HP on the drawbar and PTO?

I know that its probably a negligible amount, but I was just wondering. I've never seen any published data anywhere on overbore kits.
robably be in ball park if just ratio HP/cu in. times the added displacement; 34/134 X 4.9=1.24HP
 
Where I believe our collective minds missed the boat:

PTO HP would be measured at PTO rpm (540, or 1485 engine rpm) and if looking for engine hp, it should be measured at maximum governed engine speed ~2200rpm.
Therefore, I submit that 40+ hp for engine is a fully compatible number for 30+ hp for PTO. As for drawbar & belt pulley HP numbers, one would need to know the conditions specified for such measurements. Very likely some feet per minute belt speed, meaning not full governed engine speed and for drawbar, possibly a specified ground speed, thus setting a transmission gear & nearest engine speed to achieve, again, probably not full governed engine speed. Looking at a Nebraska tractor test will show such is the case.
 
(quoted from post at 10:12:28 10/03/14) Where I believe our collective minds missed the boat:

PTO HP would be measured at PTO rpm (540, or 1485 engine rpm) and if looking for engine hp, it should be measured at maximum governed engine speed ~2200rpm.
Therefore, I submit that 40+ hp for engine is a fully compatible number for 30+ hp for PTO. As for drawbar & belt pulley HP numbers, one would need to know the conditions specified for such measurements. Very likely some feet per minute belt speed, meaning not full governed engine speed and for drawbar, possibly a specified ground speed, thus setting a transmission gear & nearest engine speed to achieve, again, probably not full governed engine speed. Looking at a Nebraska tractor test will show such is the case.

Tractordata has the Nebraska test results. Their info on the 641 says engine hp is 48, which is likely what Ford advertised it as, because the Nebraska tests don't test at the flywheel, and engine hp is not mentioned in the Nebraska test results page, only on the main tractor data page.

On the test page they do show that the PTO was tested at various engine rpm's, including rated engine speed and rated PTO speed. At rated engine speed that 48 advertised engine hp dropped to only 31 hp at the PTO, and at rated PTO speed it dropped to 25 hp.

So if the advertised 48 engine hp was supposedly produced at the same engine speed as the PTO test that was done at rated engine speed, that's a loss of 35%, and at rated PTO speed it's closer to 48% loss, so either they designed a very inefficient tractor or the engine wasn't really producing the hp that they were advertising.
 
(quoted from post at 11:16:36 10/03/14)
(quoted from post at 10:12:28 10/03/14) Where I believe our collective minds missed the boat:

PTO HP would be measured at PTO rpm (540, or 1485 engine rpm) and if looking for engine hp, it should be measured at maximum governed engine speed ~2200rpm.
Therefore, I submit that 40+ hp for engine is a fully compatible number for 30+ hp for PTO. As for drawbar & belt pulley HP numbers, one would need to know the conditions specified for such measurements. Very likely some feet per minute belt speed, meaning not full governed engine speed and for drawbar, possibly a specified ground speed, thus setting a transmission gear & nearest engine speed to achieve, again, probably not full governed engine speed. Looking at a Nebraska tractor test will show such is the case.

Tractordata has the Nebraska test results. Their info on the 641 says engine hp is 48, which is likely what Ford advertised it as, because the Nebraska tests don't test at the flywheel, and engine hp is not mentioned in the Nebraska test results page, only on the main tractor data page.

On the test page they do show that the PTO was tested at various engine rpm's, including rated engine speed and rated PTO speed. At rated engine speed that 48 advertised engine hp dropped to only 31 hp at the PTO, and at rated PTO speed it dropped to 25 hp.

So if the advertised 48 engine hp was supposedly produced at the same engine speed as the PTO test that was done at rated engine speed, that's a loss of 35%, and at rated PTO speed it's closer to 48% loss, so either they designed a very inefficient tractor or the engine wasn't really producing the hp that they were advertising.
Yes, there is 'something' floating in the punch bowl somewhere, because no one will ever convince me of a 35 or 48% loss in a single set of 2.75:1 gear set!
Not the same engine, but it does shed some light on how such number can wind up out here in circulation. The 9N Nebraska test shows 23 belt hp @ 2000rpm and 16 draw bar hp @ 1400 rpm. Compare that to the engine graph.
 
It gets even curioser. I see down in the information below that graph it says:

"A.M.A. H.P..................................16.25

So what is A.M.A. H.P.? Googling it finds a bunch of links that says that the AMA HP rating was determined purely by a calculation using the bore, stroke and number of cylinders, and was used for tax purposes. So you could claim on your taxes that your tractor that produced 23 belt hp was a 16.25 hp tractor?
 
(quoted from post at 12:36:03 10/03/14) It gets even curioser. I see down in the information below that graph it says:

"A.M.A. H.P..................................16.25

So what is A.M.A. H.P.? Googling it finds a bunch of links that says that the AMA HP rating was determined purely by a calculation using the bore, stroke and number of cylinders, and was used for tax purposes. So you could claim on your taxes that your tractor that produced 23 belt hp was a 16.25 hp tractor?
hat ama HP is a strange beast, at one early point, in England, apparently didn't even consider stroke, simply piston area!!?
 

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