Farmall 400 2-71 Repower Project (Step by Step with Pictures)
Update Nov 5, 2018: I’ve made recent upgrades to the engine and have updated this “Step by Step Story” to reflect changes made since my original posting. Basically I ended up with coolant in the oil and head gasket compression seal leakage into the coolant. Modifications were needed. A Discussion of this now appears as a sub bullet article in the menu, 2-71 Head Gasket Issues Experienced and Background Information (https://wordpress.com/page/dieselbobllc.com/827).
Picture Story of the rebuild:
I primed the fuel system until fuel filters were full and fuel was coming out the return line. The engine fired right up with only a few turns of the crank. The above video is a typical start. I found the used old water pump and fuel transfer pump were both leaking so I have some work to do. A replacement water pump was $782 exchange so have decided to rebuild it myself for about $132 of parts. New fuel pump seals will be about $6.00.
I needed to connect connect the engine throttle lever to the tractor’s driver control lever. To achieve this I constructed a cable system where a 1/8 inch stainless cable runs from the engine’s lever to the lever on the control shaft on the opposite side of the engine through a piece of heavy wall fuel injection tubing The direction on the operator control shaft is reversed,, with up being maximum speed/power.
I plumbed the hydraulic system but had problems with the hydraulic system overheating if I increased the RPM. I added a a pressure gauge and found that at about 800 rpm the pressure regulating system jumped the pressure to around 500 psi and the regulator would not release when RPM was dropped unless I moved a control valve. I concluded this was a problem related to the very large hydraulic pump I had used from the original Allis Chalmers HD5 dozer engine. It took some research to understand the Farmall hydraulic system to decide a course of action.
The Farmall hydraulic system uses closed center hydraulic valves and uses a separate pressure regulating system that is engaged via a 3rd hydraulic control passage to the control valves. When a valve is moved, the low background pressure in the control passage is dropped and the pressure regulator raises the pressure. When the valve is returned to it’s center position the pressure is reestablished and the pressure regulator reduces the working pressure to a low level. With the very high flow rate, of the HD5 pump, the pressure drops across the pump was causing the regulator valve to raise the pressure. I briefly explored the possibility of increasing the size of a control orifice in the regulator block to try to keep the regulating system from malfunctioning, but ultimately decided to find a hydraulic pump closer to the original Farmall pumps size.
The pump I chose is a model GP-F20-25-S9-A from Dynamic Fluid Components Inc. rated at 2900 psi. The Farmall hydraulic system is regulated in the 1200-1300 psi range so the pump provides good factor of safety. I purchased it for $110 from Wholesale Hydraulic Warehouse. The pump has a displacement per revolution of 1.52 cubic inches which I estimate is smaller than the original Farmall pump that appears to be rated at 12 gpm at 1450 rpm (1.9 cubic inch per revolution). This smaller pump would have a flow rate of about 12 gpm at 1800 rpm, where I could run the 2-71 for maximum power, and avoid any chance of the system malfunctioning and overheating.
Installation of the pump required the fabrication of an adapter bracket, the modification of the drive coupling and a resizing to the attachment fittings. The revisions are shown in the following photos.
Latest pictures showing present state of the project follow, sheet metal work to be completed in the spring:
The fast hitch assembly was also in dismal shape and required extensive repair. Besides the normal rust and wear and tear on mounting bracket was broken in two and had to be welded and the one on the opposite side had been previously broken in half and re-welded withe the two halves improperly aligned. Two of the mounting holes had been torched to an oversize to allow assembly without proper support of the bolts. The following slides show how this was repaired by mounting the part, inserting a carbon stick I had threaded with a die into each hole and then welding around the carbon stick to locate the carbon stick. The bracket was removed and the carbon stick reinserted and the balance of the oversized hole was welded shut from both sides, the carbon stick removed, the surfaces ground flat and the hole lightly cleaned up with a die grinder.
In addition to the bracket repair the hydraulic cylinder was rebuilt with new seals and the drawbar, which had been broken in the middle and welded by a previous owner, was reinforced by adding a home built extension plate. This also located the hitch point to the industry standard 14.5 inches beyond the power take-off shaft.
After several months of running I found coolant in the oil and air bubbles in the radiator. Suspecting either a head gasket issue or a cracked head, the head was removed for inspection. Deterioration of the JB Weld Fix of the erosion around several of the water transfer holes had failed, as shown in the above picture. Compression gasket leakage was also observed.
Engine block deck with machined inserts set in place. Each was surface ground for flush mounting. Anaerobic sealant was used under each insert just prior to assembling with a new head gasket. Note, liners and pistons were removed for the modification.