7020 PS with Cummins 5.9 transplant

captaindana wrote: Dr Allis is the most amazing…..

Was the stock engine unreliable?  Are repair/replacement parts for it now hard to come by or too expensive?  Other than the extra horsepower and the availability of Cummins parts I'm wondering about the motivation to do this swap.  As I said, just wondering.

Back in 1989 when my 731 literally blew up I was forced to make a call whether to fix it or replace it. Those tractors and mainly the engine had a really bad reputation at the time. After doing the repower I sent a writeup to Farmshow magazine and had 12 or 15 calls back about how the repower worked out and if it was worthwhile etc etc. Several callers comments were that they had one or two of these tractors parked in the weeds with 1200 - 1500 hours and a blown engine and they didn't know what to do with them. Not everyone had the time and people that I did to engineer a repower. I recall that parts were crazy expensive like $1200 a hole for sleeves and pistons compared to about that much for a whole set of 6 for a Cummins 855. Considering that I needed a block ($6000) and crank ($6000) and those were hard to come by because that was what failed on most engines, it just was not feasible to go the route of the AC 731. I could buy a new Cat 3306 with a bell housing that bolted right up to the Allis transmission for about $15,000 but it was on the small side of what I needed. A complete rebuilt NTC 350 with access to wrecking yard parts for bell housing, flywheel, clutch parts, motor mounts, fan hub, accessory brackets, air intake pipe and elbows, linkage parts and all the little things that you need for $10,000, made the choice easy.

My understanding of AC history in the industrial line of equipment was that they had the 844 cu in Budda Lanova engine which was a very good well built long life engine when run at 1600 - 2100 rpm like all the other main US brands Cat, Cummins, 60 Detroit, etc. The 844 or 6138 or 25,000 had a bore of 5.25 and stroke of 6.5". The 731 used the same block with a bore of 5.25 and destroked to 5.625". Originally the 844 ran 1400 rpm with max hp of 197 and torque of 740 ft lbs. Later as a purple Mack FS-700 truck engine they made 375 hp and some were juiced to 675 hp. The 731 and 844 were the same block and bore and weighed 5900 lbs according to one report. Way more than modern Cat or Cummins engines. None of the others ever had a version that the high idle speed was 2800 rpm. As Dr Allis suggests the transmission used in the 4WD Allis tractors was just a modified version of the 7000 and 8000 2 wheel drive tractors and was not able to take the torque of a big industrial engine at normal speed of 1800 to 2100 rpm. I learned the hard way that by running the 8550 transmission in 5th gear, low range in the drop box and low range in the power director clutches, you were flowing the power straight through the transmission and it would take the torque fairly well. That was about 5 mph I think. So because of the economic uncertainty of building new a 4WD tractor line at that time in history, just as the great depression of the 80s was about to hit North America, AC chose to "cheap out" and speed up the engine to crazy rpm to reduce the torque down to where the transmission had a chance of not melting down. I had a discussion with 427435 another very smart Allis guy on this forum about that very thing. He referred me to a book that explained what was going on in America at that time that led to the collapse of numerous old successful companies like AC, IHC, Versatile, Steiger, and a long list of companies that had been around since the beginning of the industrial boom in North America. The inflation of the 70s came to a head and Volkers 20% interest rates was needed to stop the runaway train. Companies had gotten used to ever increasing wages, costs, retirement plans, unproductive policies that made them all unviable in the new reality of the mid 80s. I believe I heard that in some of those years there were only 1200 4WD tractors in total of all brands sold in some of those years. I miss 427435 for his knowledge and insight but anyone can read what he spoke of in the book
"The Turnaround Experience" by Frederick M Zimmerman. A worthwhile book to own and take to heart as we enter another inflationary and dysfunctional period of history.



There is another thread from a few years ago that discusses some of this if you are interested "6138 truck engine" topic 74441

So dr,what would be the best engine for replacement for the 8550?
Maybe 300hp 8.3 cummins turning 2400rpm?

After Case bought IH in about 85 they started using 5.9 Cummins instead of IH 466. The IH could handle 2600 rpm in the 1480 combine but at that speed the 5.9 didn’t have good pulling power and often had pistons come apart, skirts coming off. By 1993 Case redesigned the rotor drive up to triple C belts and slowed down the new 8.3 to 2150 or 2200 rpm. Much better setup and allowed the 8.3 to produce 260 hp. I wouldn’t run a Cummins that fast. Are there any CR or KR Steigers around the wreckers? They used a 3306 at about 270 hp or L10 at around 280 hp and had the AC 20 speed power director. Either would be a better match to the tractor. Or I could just sell you my 8550 with the 855 Cummins already installed.

No authority here but my 4000+ hr R62 8.3 is 2400 and change high idle and runs 22-2350 all day in field. I'm 3rd owner but I believe head gasket replacement Last summer and rod and mains is its only maintenance.

The first Cummins equipped axial flow combines ran the engine at 2700-2750 RPM's. They had some engine problems running them this fast, so the later models they slowed the engine down to 2500 RPM's .

2700 is not real fast for an IH 400 series diesel. Had the pump on my 1460, 436 cid, rebuilt this year. Tag says Idle, 1000/2500. Top number must be working speed as it high idles about 2750.

In the 1680 combine the 8.3 ran at 2600 rpm and that was later slowed to 2400 rpm in all the 88 series.  Spent many hours behind the wheel of these machines.  Usually the high rpm motor would blow at around 3500 hrs.   The slower version was much more reliable.  The 8.3 in my MF 8570 is rated at 2300 rpm.