Well my friend Clifford has offered me his help for the last several years to help me cure the black smoke the bus has been belching, so I headed to Mohave Valley, Az. in March 2013 to tackle the job. The result has been a complete training class on 2 stoke diesel basics and a total rebuild of the engine.

Get ready for more than you ever wanted to know about the Detroit Diesel 8V71!

The Series 71 engine was developed by Detroit Diesel in 1938. Well prior to electronic controls, it has lasted 75 years in service around the world. Clifford has been working on them for most of his life, and he remembers when the overhaul kits were sold in local drug and grocery stores. If you had a 6 cylinder engine, you bought 6 kits. Eight if you had a 8V71.

It is still under contract to be used by the U.S. Army in self-propelled guns until 2025. They don't care about EPA or pollution... they want the most dependable equipment around.

It requires only 2 key elements to run; air and fuel. Keep it cool and lubricated and it will run almost forever. These are million mile engines, you know. So with that in mind, I assumed that in a normal healthy engine, black smoke is the result of unburned fuel. You see that when a big truck goes uphill and "pours the coal" to it. That's excess fuel going out the exhaust.

So for the last 5 years, I've tinkered with adjusting the amount of fuel by downsizing the injectors and having various folks tune and detune the engine. After all, the previous owner had done a complete overhaul less than 50,000 miles ago. I'd finally come to the conclusion that the problem was insufficient air volume and the only person I know that could check it out right is Clifford. He's in Mohave Valley, Az. just across the Colorado River from Needles, Ca. and about 100 miles south of Las Vegas.

It was mid-March 2013 when I got to his shop. He'd been helping another BusNut, as we'er known, who'd blown his engine in a 4106 GMC. Red Rider as he's known is from Utah. Mike and his friend Dan were wrapping up their rebuild so Coffee and pitched in to help a little while I took our place in the que. Mike and Dan had to come down on weekends so while we waited Clifford got the valves adjusted and the rack run. This was my first real hands on experience with a "tune-up." Within short order, Clifford was helping me once more. You may remember my breakdown in ShowLow and my last visit to Mohave for maintenance and repairs.

He agreed that it was probably an air problem so we pulled up the bed and dove into the engine from the top from inside the bus. It was off with the blower for a rebuild. Pretty straight forward, for HIM, just take it apart, replace the seals, clean it up and off to the races. And before you knew it, off with the Jake brakes, rockers, bridges and injectors. The first signs of real trouble were that there was an awful lot of sludge and grime in the air box, but having never seen the inside of a Detroit which are notoriously nasty, it seemed normal to me. There were some troubling signs of over tightened bridges and valves. (More on bridge adjustment later.) And most puzzling was uneven wear marks on the relatively new injector heads. Somewhere along the way someone had ground the rockers by hand and only the edge of the rocker was catching the injector plunger. Clifford went to the first of his parts stashes and replaced the rockers.



The Blower Project is Next...

 

For all our major stops see our Travel's Page.
More in days to come about the total rebuild.