Detroit Diesel — Valve Lash and Injector Adjustment
Adjustments · Valve train, fuel injectors, Jake Brake
From a Detroit Diesel service manual — check it applies to your exact model before use.
Before you start
- ELECTRICAL SHOCK: To avoid injury from electrical shock, do not touch battery terminals, alternator terminals, or wiring cables while the engine is operating.
- EYE INJURY: To avoid injury from flying debris when using compressed air, wear adequate eye protection (face shield or safety goggles) and do not exceed 276 kPa (40 psi) air pressure.
- NOTICE: Never set the valves and injector of the same cylinder at the same time. Doing this will result in engine damage.
- NOTICE: To prevent cylinder head from cracking when bolts are torqued, remove the oil from the bolt holes.
- NOTICE: Installing 170 mm cap screws on the exhaust side of the engine can result in serious engine damage.
- Electrical Shock: To avoid injury from electrical shock, use care when connecting battery cables. The magnetic switch studs are at battery voltage.
- Failure to measure valve clearances at the required initial period and make necessary adjustments may result in gradual degrading of engine performance and reduced fuel combustion efficiency.
Procedure
- Disconnect batteries.
- Remove the engine valve rocker cover (refer to section 1.6.2 two-piece or 1.6.3 three-piece).
- If equipped with Jake Brakes, remove the electrical connections at both brake solenoids.
- Loosen retaining bolts (1-6) and nuts (7 and 8) one turn at a time so as not to damage rocker shaft or cylinder head.
- Remove the Jake Brake retaining bolts (1-6 and 9-14) and nuts (7 and 8); remove the Jake Brake and set aside.
- Attach tubing to an air gun nozzle and blow oil out from the rocker shaft bolt holes (max 276 kPa, 40 psi).
- Lubricate each hold-down cap screw with clean engine oil prior to installation.
- Install three 170 mm (6.693 in.) long cap screws on the rocker shaft using the Jake Brake spacers from the exhaust side of the engine.
- Tighten cap screws and spacers equally until rocker shaft is against the cylinder head.
- Torque starting with the middle cap screw on the camshaft, sequence bolts (1-6) and nuts (7 and 8), to 55 N·m (40 lb·ft); final torque all to 102-126 N·m (75-93 lb·ft).
- Insert a 3/4 in. drive breaker bar or ratchet into the square hole in the center of the crankshaft pulley and bar the engine in the direction of rotation.
- Mount a magnetic base dial indicator on the injector cam roller; bar the engine until maximum injector roller lift is obtained.
- Note which cylinder this is and follow the Table 2 sequence to correctly set injector and valves.
- Adjust the injector: loosen the locknut at least two full turns; tighten adjusting screw until plunger bottoms out to 4.51 N·m (40 in·lbs); back off 3/4 of a turn (0.75 mm ± 0.25 mm); torque locknut t
- Adjust the intake valves using a 0.203 mm (0.008 in.) feeler gage and the exhaust valves using a 0.508 mm (0.020 in.) feeler gage; torque locknut to 41-47 N·m and re-check with the feeler gage. Repeat
Tools required
- Feeler gage 0.203 mm (0.008 in.) Amazon
- Feeler gage 0.508 mm (0.020 in.) Amazon
- Magnetic base dial indicator Amazon
- 3/4 in. drive breaker bar or ratchet Amazon
- Torque wrench Amazon
- Air gun with tubing Amazon
- Allen wrench Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Rocker shaft stud torque 126-146 N·m (93-108 lb·ft)
- Initial cap screw/nut torque 55 N·m (40 lb·ft)
- Final cap screw/nut torque 102-126 N·m (75-93 lb·ft)
- Injector adjusting screw torque 4.51 N·m (40 in·lbs)
- Injector adjusting screw back-off 0.75 mm ± 0.25 mm (0.03 in. ± 0.01 in.)
- Injector/valve locknut torque 41-47 N·m (30-35 FridayParts $14.81 KuduParts $233.00 lb·ft)
- Intake valve clearance 0.203 mm (0.008 in.)
- Exhaust valve clearance 0.508 mm (0.020 in.)
- Solenoid screw torque 1 N·m (9 in·lb)
- Compressed air pressure max 276 kPa (40 psi)
Source: Detroit Diesel service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.