Setting Valves On A Diesel Engine Without A Manual

Mechanics Hub - June 13, 2014
Inline Six Diesel Engine Valve Adjustment

There is a way without having a manual to adjust the engine valves on any inline diesel engine because of the universal design that makes it easy to carry out this procedure. This procedure is called the rocker method that uses the intake and exhaust valve position as a reference while turning over the engine by hand. The position of the engine will be at top dead center (TDC) and it depends on valve position that determines which cylinder is ready for adjustment.


Engine Configuration

With an inline 6 diesel engine piston #1 and #6 rise and fall together in their respective cylinders as does pistons #2 and #5 and #3 and #4 pistons. You could call these pairs sister cylinders....1 and 6 cylinder for example will have both pistons at TDC but one will be on the exhaust stroke while the other will be on the compression stroke.

The Rocker Method

So using the rocker method I usually start at #1 valve adjustment since the firing order on all inline 6 engines is 1 5 3 6 2 4. To get to the #1 cylinder valve adjustment bar the engine over and watch the valves at cylinder #6. You will see the exhaust valve closing...... just when it's totally closed the intake valve will JUST start to open (commonly known as valve overlap). This indicates that both #1 and #6 pistons are at TDC but #1 cylinder intake and exhaust valves are on the compression stroke and ready for adjustment while #6 cylinder is on the exhaust stroke.

Following The Firing Order

The next cylinder in the firing order is #5. Turn the engine over until cylinder #2 exhaust valve closes and intake valve JUST starts to open. Just as #1 and #6 pistons were at TDC together #2 and #5 pistons are now at TDC. It will take 2 rotations of the engine to adjust all of the valves. Every 120 degrees of crankshaft rotation will position the engine properly for each adjustment.

Why Use The Rocker Method?

Of course there is the factory method where in the case of the DT466E engine pictured you line up the reference mark on the timing cover and vibration dampner which is TDC. In this position you can adjust half of the valves. Rotating the engine 360 degrees will set the engine up for the remaining valve s for adjustment. The main reason for the rocker method is when you don't have the manual handy and know the valve clearances. I would like to see your comments below if you have any experience using this method or just have feedback or a question.
Diesel Engines