426 Limitations/Flaws

OH my my- geesh

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.

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.

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.

Get a Hercules 426 from a 2150 Oliver the engineering has already been done

DrAllis wrote: 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........

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.