8550/4w305 Dyno test

Hi a’ll!!
So I’m just curious on how many hps that engine cranks out on a dyno. I know the book says 305 hps but I read somewhere that a original one dynoed at 425hp whether that’s true or not…

The 450 HP version. Might that have been the 844 designated as the model 25000?

NO. Only the 731 was used in the 8550/4W305.

Edited by DrAllis - 27 Sep 2023 at 9:16pm

55allis wrote: Hmm, would the 844 bolt right in a 8550/4w305? Not that I have one but I’m just naming off ideas…

Was the transmission for the 8550/4W305 specifically made for this tractor, or was it reworked from the 7000 series? If the transmission was specific to the 8550/4W305, why not make it heavy enough to start with?

Thanks Doc for your input!!!
If I ever got one with a shot engine (or needs rebuilt) I’ll know what to do…
I hope this encourages others to go Allis instead of some other brand.
I’d love to have one with twin stacks!!!
But money speaks first….

Thanks for the info. I supposed they didn't sell enough, to justify a whole new transmission.

Sorry Doc, I guess I misunderstood what you meant. That makes sense.

I don't know what torque numbers or HP numbers and any changes that may have been made to the transmission for that particular Steiger application. Obviously Allis didn't want their rated speed that low and it may have only been for the hydraulic pumps they chose to use. Can't tell you.

DrAllis wrote: For those who aren't aware of the early troubles with the 8550 engine, the 2700 RPM high idle was the cause of the early and somewhat lingering engine problems. The first engine campaign involved replacing all the pistons, because they couldn't stand the RPM's.  Replacement pistons were beefed up in the pin boss area. Then, they found out the valve rotators were flying apart, which vomited little tiny valve springs into the oil pan, which would get sucked up by the oil pump. Both problems because the tractor engineers needed the engine to rev pretty fast so their transmission could hold up. This 731/844 engine was made for 2100-2200 RPM top speeds and the tractor division didn't want things that slow. So, for those thinking an 844 in an 8550 will work fine, just remember the transmission was made for 300 engine HP @ 2500 RPM and that's all. If the driveline would have held up to 400 HP, Allis would have made one at that HP rating, which they DIDN"T.

About where is your location DrAllis? I was working in Audubon, IA during the updates. We had Joe Dullard as a factory rep.

I owned and farmed with a 8550 for 20 some years. The 305 is the gross engine horsepower. AC marketed them as having 253 pto horsepower, which mine easily achieved the couple times I had it on the dyno. I updated the valve rotators to a CAT part number which are superior in design. AC should of used the proven and much more reliable 844 cubic engine, but from a cost standpoint I understand why they did what they did. I also tuned the injection pump to the specs. of the 4W305, which helped wiith upper driveshaft vibration and my peace of mind. I also have a 7080 and I could tolerate the 426 spinning that fast, but running the 731 @ 2700 hi idle , never seemed right to me. Just some of my many experiences, Mike     

I purchased a set of used piston's from Paul Gain. Still have his add that I cut out of farmers hotline. I got over 2000 hours out of them. He also came up the CAT valve rotator, replacing the inferior oem's from AC.

Just for reference here, this engine family was bought by AC in 53 from BUDA.  When the crawler line got the engine in 1955 replacing the 6-71 and 6-110 detroits,  these engines were turning 1700 rpm in the direct drive machines and 1800 in the converter crawlers.  HD16 and HD21    

Edited by CAL(KS) - 05 Oct 2023 at 7:41am

We got a call one Janurary at the dealership from Dave Arps from Memphis region. He ask us to pick up the 8550 at the Loretta Lynn Farm and do what was necessary to pull it in the new 4wd class at the National Farm Machinery Show at Louisville. Kind of stunned and knowing a tad about pulling I ask him why - it wasn't going to be pretty. He said he had some information that we would not be embarrassed - gave me the # to Terry Wood at the engine plant .  Later I found out the information came from Jerry Baird who worked for AC and was on the pull board - he was instrumental in making the pull as famous as it was and safe as well. So we did, and had an interesting time on the dyno - the larger M&W -which would not hold the unit as it tried to flip the dyno as it maxxed out. Terry advised us to loosen the set screw on the top of the pump and run the screw to allow the rack to travel until the engine went 'sour' which meant it had gone into cranking reetard.  We did but I did not lock the plate one time trying to find the max setting - the 8550 almost died - black smoke came out and it sounded like the engine was blown .  We were relieved to find the stop plate had vibrated all the way back- a little more playing and we had it set. We had to remove all the weight we could from the rear and add to the front but we could not get to he % we wanted w/o major surgery.  We added two exhausts and frame to hold them,  fabbed a hitch to specs and off we went - along with another 8550 we set up which belonged to Mac Bagget from around Springfield Tn.  I don't remember what gear we ran but we didn't phase the engine RPM which never reached 2600. I was told not to shift but with the sleds of the day which did not drop the pan we hit high range button and still spun out.  Could have gone up 2 more gears. We just didn't know as we were rookies.  We placed 5th behind 2 Versatiles with the 903 Cummins and an 8550 that was really hot and all were veteran pullers.   Mac's 8550 was 7th I think.  Hey - we got a check ! ( a fraction of the investment )  My plaque burnt up in the fire.  That was one in the 'bucket' .