How to adjust the valve of V8 diesel engine?
1, find cylinder compression top dead center.
Among the six diesel tractors, except LT665, all other models are looking for a cylinder to compress the top dead center. The method is as follows: GBC pry the crankshaft according to the rotation direction of the engine. Observe the exhaust valves of three cylinders at the same time. When the valve starts to open, the piston of one cylinder is at compression top dead center. GCH, CQ26 1 and SX250 pry the crankshaft according to the rotating direction of the engine, and observe the intake valves and exhaust valves of six cylinders at the same time. When the intake valve and exhaust valve of the cylinder act at the same time and the ends of the two valve rods are flush, the top dead center compresses a cylinder; LT665 pry the crankshaft according to the rotation direction of the engine until the 0-degree marking on the edge of the pulley at the front end of the engine is aligned with the pointer fixed on the engine block, and then 20 degrees from left to right. At the same time, observe the push rods of the intake and exhaust valves of the five cylinders. If they are basically motionless, it means that the piston of the cylinder is at compression top dead center. Otherwise, the crankshaft needs to be rotated once, so that the 0 scribed line is aligned with the pointer, and the five-cylinder piston is at the compression top dead center. Benz2026 turns the crankshaft with a quick wrench according to the running direction of the engine, and observes the valves of six cylinders at the same time. When the intake valve and exhaust valve of a cylinder are opened with the same opening, the piston of one cylinder is at compression top dead center.
2. Identify the intake valve and exhaust valve, and select the clearance value.
There are two ways to arrange the cylinders of diesel engines. In-line cylinders count from front to back. Looking forward from the rear end of the V-engine, the right row is 1, 2, 3, 4, and the left row is 5, 6, 7, 8. See table 1 for the arrangement order of several diesel engine cams. It should be pointed out that the 8 120F engine has two camshafts. See Table 2 for the clearance of intake and exhaust valves of various vehicles in cold state.
Table 1 Cam Arrangement Order of Several Diesel Engines
Arrangement sequence of diesel engine model cams (from front to back)
6 140-B
MC640A, go in, go in, go in, go in.
6 130
M520B, line, line, line.
5 lines 1 into 5 lines 1 lines 6 lines 2 into 6 lines 2 into.
OM402
7 rows, 3 inches, 7 inches, 3 inches, 8 inches, 4 inches, 8 inches and 4 inches.
Look at the left camshaft at the flywheel end. Row in, row in, row in, row in.
8 120F
Right camshaft in and out, in and out, in and out.
3. Determine the expression method of adjustable valve.
Taking a six-cylinder diesel engine with the power sequence of 1-5-3-6-2-4 as an example, the expression for calculating the adjustable valve is shown in Table 3.
Table 2 Valve Clearance of Diesel Engine (mm)
Naming intake and exhaust valves
type
6 140-B
MC640A
M520B 0.25 0.35
OM402
6 130 0.25 0.30
8 120F 0.05 0. 10
Table 3
The rollers are pressed into overlapping rows.
Working state fire contraction and gas opening work.
sign
Cylinder number 1 5 3 6 2 4
Adjustable valve intake, exhaust and exhaust.
The expression reveals the internal relationship between the working cycle of diesel engine and whether the valve can be adjusted: the intake and exhaust valves of ignition cylinder can be adjusted; The intake and exhaust valves of the stack are not adjustable; Exhaust valves of intake and compression cylinders are adjustable; The intake valves of the power and exhaust cylinders can be adjusted. Because of the continuity of the working cycle, as long as any cylinder number is written under the expression symbol "□" and other cylinders are written under the corresponding symbols according to the working order, you can know what state each cylinder is in and which valve is adjustable. Turn the crankshaft once, and the original overlapping cylinder becomes the ignition cylinder. As long as the 6-4-2 in the above expression is moved to 1-5-3, the remaining valve clearance can be adjusted. This method is also suitable for four-cylinder, five-cylinder and eight-cylinder diesel engines. For a five-cylinder diesel engine, it can be assumed that one cylinder works after three cylinders.
4. Adjust with the specified clearance value.
When finding out the compression top dead center of a cylinder (8 120F is five cylinders), insert a thickness gauge between the valve stem end and the valve rocker head according to the expression method, so that the thickness gauge can move back and forth slightly, preferably slightly blocked. If it does not meet the requirements, it needs to be adjusted. The specific adjustment method is as follows: firstly, loosen the lock nut on the rocker arm slightly, then turn the adjustment screw with a screwdriver as needed to make the downward (right) clearance smaller and the upward (left) clearance larger until the rocker arm and the valve contact with the thickness gauge and can still move, then fix the adjustment screw with a screwdriver, tighten the lock nut, then move the thickness gauge and turn the crankshaft for recheck until the valve clearance values are correct.