Over the valley and through the woods

After purchasing the bus I traveled regularly over the hill from Carson City to Georgetown to begin work on the bus. Our plan was to get the original 6v71 Detroit engine running so we could move the bus around. I am by no means a diesel mechanic so taking a stab at the Detroit was definitely going to be a learning curve. Before working with this engine my belief was that all diesels had glow plugs to ignite the fuel, I was very wrong about that. As it turns out the Detroit engine is a 2-stroke diesel. The engine has no intake valves and creates no cylinder pressure on its own. Instead, a roots type blower sits atop the motor and is gear driven to produce pressure within the engine block. Vents in the side of the cylinder lining take in the crankcase pressure when the piston is down then creates compression. Upon full compression a mechanical fuel injector squirts fuel into the pressurized air and creates ignition. I hope I explained that well enough. For me, knowing my equipment really helps me to understand what I'm doing and become more proficient at working on it. Anyone who is looking into converting a bus that has one of these engines in it can learn to work on one. As far as engines go, this one is as simple as it gets.

The California humidity had taken its toll on the engine's paint. Although it was weathered, it was all there.

My first time messing with a mechanical injector. The fuel flow is controlled by a rack that opens and closes the injector. Fuel delivery is controlled by a rocker arm that pushes down on the poppet valve on the top of the injector. Each injector has a fuel feed and return line.

Time was taken to properly ultra sonic clean each injector and test its spray pattern before re-assembly and rack adjustment. This engine was rebuilt once back in the late 70s by Greyhound. As you can see by the stamping this injector was installed 9/70.

A peak inside of the rocker box of the 6v71. Each cylinder features 4 exhaust valves. Here you can see the rocker arms that control the fuel injectors as well as the fuel feed/return lines, and the "rack" which controls the throttling of each injector.

Greyhound engine rebuild tag. Rebuilt 2/27/1978.

654,712 miles on the engine before it was rebuilt in 1978. That's 50,362 miles a year!

Looking down on the throttle linkage and governor housing on the front of the blower.


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