426 Limitations/Flaws
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=205874
Printed Date: 16 Mar 2025 at 3:23pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: 426 Limitations/Flaws
Posted By: joe
Subject: 426 Limitations/Flaws
Date Posted: 15 Mar 2025 at 10:06am
| Just got thinking about this recently. By no means flaming the 426, just thinking that compared to engines today (which may not be a fair comparsion), that the 426's output is quite low, and that when they pushed the envelope, it didn't really work out that well. (Consider the 6.7 FPT, that very reliably makes 270 hp. They make more power than that, but are being pushed I think, and don't have much grunt.) What is it about the 426 that really limits it's upper HP? Meaning, what was it about the 7080's and 7580's that really limited their longevity? I've read that the speed they ran them at caused trouble. Why run them at those speeds? Seemingly, it the only way to get more HP. Why? Could they be built to run a reliable 220 HP, say in a 7580? Bigger rods, larger big end fasteners, rod journals(new, redesigned crank)? Girdle? Just musing. Just to clarify, I have a soft spot for Allis stuff, so I am not trying to start a war, just curious if anything could be done, short of replacing the block, to improve them, leaving cost out of it. |
Replies:
Posted By: DougG
Date Posted: 15 Mar 2025 at 10:31am
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OH my my- geesh |
Posted By: DSeries4
Date Posted: 15 Mar 2025 at 10:35am
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Holy crap! This has to be the biggest case of comparing apples to oranges I have seen in a long time. You are trying to compare a diesel engine that was first introduced in 1963 to an engine of today??? Fuel management and it's technological advancement have a lot to do with the increase in power. Mechanical fuel injection versus computer controlled. 12 Valve versus 24 valve. It's ability to breathe. Many different factors. 426 Engine life was reduced when high idle was increased over 2500 rpm (2800 in the 7080) to squeeze more power out of it. It simply was not designed to run that fast. ------------- '49 G, '54 WD45, '55 CA, '56 WD45D, '57 WD45, '58 D14, '59 D14, '60 D14, '61 D15D, '66 D15II, '66 D21II, '67 D17IV, '67 D17IVD, '67 190XTD, '73 620, '76 185, '77 175, '84 8030, '85 6080 |
Posted By: Acguywill
Date Posted: 15 Mar 2025 at 10:47am
| I think Joe's basic questions are what can be done to a 426 to make it last at higher hp? And can it be made to be comparable to a modern engine? I am not an engineer or an engine builder so have no ideas for what could be done. |
Posted By: joe
Date Posted: 15 Mar 2025 at 10:58am
| I would say this is what I'm after. Keeping the block, could the 426 be made to live a long happy life at 220 HP? 200? 180? If a person were to make a 4 valve head with a HPCR fuel system, could you make it breathe better, live longer, have fueling that would be more gentle on the engine (a number of smaller injections per power stroke)? Does it have the strength to run 200 HP at 1800 RPM, if you were to have a crank with larger rod journals? Just hypothetical. If we replace even the block, there's nothing left that really makes it an Allis 426. |
Posted By: DrAllis
Date Posted: 15 Mar 2025 at 11:10am
| The Allis-Chalmers Harvey, Illinois engine division introduced the two "new" mid-range 2000 and 3000 series engines in 1964 (200/265/301) and 1963 (426). I imagine the development for these new power plants began at least two years prior to their release and maybe longer. These were truly brand new designs and not "warmed over" old Buda engines. With the introduction of the new generation 3010 and 4010 John Deere tractors in the Fall of 1960, I imagine it became all-hands-on-deck at the Harvey plant to come up with something that could compete with the new Waterloo built engine line. I doubt very much that any of the engineering teams involved, ever imagined that these new engines would have their original HP release levels nearly doubled over the next 20+ years of production. The original 426 NA in a D-21 tractor would have been 115 flywheel HP @ 2,200 RPM. By the end of their production in 1985 or so, the 426 turbo and intercooled configuration in a 7580 tractor was rated at 222 flywheel HP @ 2550 RPM. These are the facts. Now, for the opinions. All those years and increasing HP ratings never got any serious design changes for durability. What was needed was larger main and rod bearing journal diameters to add strength to the bottom end of the engine. This would have required different castings and forgings, all of which cost money. It also would have separated the commonality and interchangeability of new parts in older engines. The best time to have made this change would have been (in my opinion) the intro of the 7030-7050 tractors in 1973 which was the beginning of the "Mark II" series. One of the reasons for the 2800 RPM Hi idle at 2550 RPM rated speed was to help the life of the tractors transmission input area, along with keeping the crankshaft components in a better torque handling speed range. In the end, the speed and HP increase really seemed to hurt the engines overall life at those higher HP levels. Flywheel HP levels left at 175 @ 2200 or 2300 RPM seems to yield much better longevity for sure. |
Posted By: injpumpEd
Date Posted: 15 Mar 2025 at 11:57am
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I've always felt, the short cylinder head height has always been the 426 biggest hp limiting factor. They should have cast it an inch taller. It also should have been upped to 466 cid. I have a 479 CID AC 426 in my puller, and it makes over 800 flywheel hp on the dyno. It could never be farmed with that way though, it doesn't even have coolant in it anymore lol! I guess it's like a Deutz in that respect, being "air cooled" lmao! ------------- 210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers! |
Posted By: DrAllis
Date Posted: 15 Mar 2025 at 3:08pm
| Agreed on the cylinder head height and/or a four valve design. Agreed on a more modern fuel system. BUT, these things can contribute to even MORE torque and HP output, which only puts more stress and strain on the bottom end, which has all it can stand as it is now. As an example, an old DT-436 Farmall's crankshaft was counterbalanced and had 3.375" mains and 3.00" rod journals with the same 5 inch stroke. It too ran 2800 RPM and didn't suffer the bottom end problems the 426 did. Crank was stronger and main caps were taller for strength. It wasn't ever taken past 175 flywheel HP either. They had a 466 for those applications. |
Posted By: AaronSEIA
Date Posted: 16 Mar 2025 at 7:17am
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As I understand it, the bottom end was the weak point. Serrated caps and better rod bolts would have kept the bottom end together. After that I'm not sure what 1970's era engine design theories would have helped. Easy to try and apply 50+ year newer ideas to that old block. AaronSEIA
|
Posted By: Gary Burnett
Date Posted: 16 Mar 2025 at 8:02am
| Get a Hercules 426 from a 2150 Oliver the engineering has already been done |
Posted By: DrAllis
Date Posted: 16 Mar 2025 at 8:06am
| Every brand, make and model of piston type engines ever made have had occasional instances of a "rod out thru the side of the block". That's just a fact. A-C engines are really no better nor worse in that department. Oliver 310/Waukeshaw engine were KNOWN for that. If you have a worn out conn rod bearing, that could certainly cause a hole in the block. I never re-use rod bolts. Many modern engines require rod bolt replacement once used. I guess I've been ahead of technology on that issue. Serrated rod caps introduce the element of cleanliness when being assembled. Anything left in the joint will eventually loosen and fail. What I was referring to was broken main caps, broken crankshafts and accelerated main/rod bearing wear when the HP and torque levels get up to a certain level. And never forget, an engine that is set at 250 HP and is never subjected to that much of a load hour after hour because of an operator who doesn't tend to work the snot out of that engine, will last longer !!! |
Posted By: NEVER green
Date Posted: 16 Mar 2025 at 8:31am
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I think after the crankshafts were strong enough if Allis did NOT cold roll them, regrinding them brought hazards. How often did the West German ones break?? The latest drilled rods were beefy enough in my book. ------------- 2-8050 1-7080 6080 D-19 modelE & A 7040 R50 |
Posted By: DrAllis
Date Posted: 16 Mar 2025 at 8:39am
| I've never had one, but have heard of N-6's that ventilated the block. I'd always assumed that rod bearings were WORN out from high HP output day after day, oftentimes due to a processor and configuration of the rotor that caused the engine to produce 20+ psi or more of boost all day long to get anything harvested. All my N-series would run a 6-30 CH at a fast ground speed and hover around 15 to 16 psi boost. Which engine will last longer ?? And I can only imagine how long an N-6 rod bearing was hammering before it let go with the engine 20 feet from the cockpit and a full bin of grain in-between to dampen the noise. And then there's the radio........ |
Posted By: NEVER green
Date Posted: 16 Mar 2025 at 8:59am
Thats a very "sound" theory. I run Ford rods in my puller that have 1/2 inch bolts, seem huge in comparison. ------------- 2-8050 1-7080 6080 D-19 modelE & A 7040 R50 |
DrAllis wrote:Posted By: NEVER green
Date Posted: 16 Mar 2025 at 9:04am
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Another weak point is that hole for the distributer and that oil squirter hole to no where, WTH? ------------- 2-8050 1-7080 6080 D-19 modelE & A 7040 R50 |
Posted By: DrAllis
Date Posted: 16 Mar 2025 at 10:47am
| I always assumed they actually made some natural gas/spark plug engines. When designed in 1960/61 that sure was a probability. Minnie Moe sold thousands of 504/585 cube LPgas engines during their years of engine building. |