Valve Adjustment

Adjust valve lash on the 8.0L V10 engine to restore proper valve train clearances using mechanical screw adjusters and locking nuts.

Warnings

Tools required

Parts

• Valve cover gaskets (set of 2) × 1 — Use OEM specification
• Valve cover bolt grommets × 1 — Use OEM specification

Preparation

1. Ensure engine is completely cold (preferably overnight cool-down)
2. Park vehicle on level surface and engage parking brake
3. Disconnect negative battery cable
4. Remove engine cover panels if equipped
5. Gather all tools and replacement gaskets before beginning

Procedure

1. 1

   Remove air intake components
   Disconnect air intake tube from throttle body. Remove air filter housing and any intake ductwork that interferes with valve cover access. Disconnect any breather hoses connected to valve covers. Label all vacuum lines and electrical connections before disconnecting.
2. 2

   Disconnect ignition components
   Disconnect spark plug wire boots from all 10 spark plugs. Label wire positions (cylinders 1-10) for correct reinstallation. Remove spark plug wire retaining clips from valve covers. Disconnect any ignition coil connectors if they interfere with valve cover removal.
3. 3

   Remove valve covers
   Remove valve cover bolts from both cylinder banks. There are 10 bolts per valve cover. Carefully lift valve covers off, breaking gasket seal if necessary. Set covers aside on clean work surface. Do not pry against gasket sealing surfaces.
   Torque spec

   Cover Bolts16 Nm (12 lb-ft)
4. 4

   Inspect valve train components
   Visually inspect rocker arms, pushrods, and valve stems for wear or damage. Check for oil sludge buildup. Clean valve train area with shop towels if needed. Verify rocker arm retaining bolts are secure and torqued to specification. These non-adjustable rocker arms require no lash adjustment.
5. 5

   Position cylinder 1 at TDC compression stroke
   Positioning cylinder 1 at TDC compression is only relevant for inspection/service reference. Note that with hydraulic lifters there is no measurable rocker looseness at any crankshaft position. Timing mark on damper should align with TDC mark on timing cover. This is the starting position for valve adjustment sequence.
   ⚠Only rotate engine clockwise. Confirm both valves are closed before proceeding - if one valve is open, rotate crankshaft one additional full revolution.
6. 6

   Adjust valves for cylinders 1, 3, 5, 7, 9 (firing order group 1)
   This engine uses hydraulic lifters with non-adjustable rocker arms. No valve lash adjustment is performed. Rocker arm retaining bolts are torqued to specification only; no feeler-gauge clearance setting is required.nd tighten lock nut. Verify feeler gauge still has slight drag after lock nut is torqued. If clearance changed, loosen lock nut and repeat adjustment.
   ⚠Feeler gauge should slide with light resistance - not loose or excessively tight. Excessive force indicates incorrect adjustment.
   Torque spec

   Valve Lash Adjusting Screw Lock Nut20 Nm (15 lb-ft)
7. 7

   Rotate crankshaft 360 degrees
   Rotate crankshaft clockwise exactly one full revolution (360 degrees). The timing mark should return to TDC position. This positions the remaining cylinders for valve adjustment.
8. 8

   Adjust valves for cylinders 2, 4, 6, 8, 10 (firing order group 2)
   This engine uses hydraulic lifters; there is no second-position valve adjustment. No feeler-gauge clearance setting or lock nut torquing is performed on any cylinder.
   ℹ️Double-check each valve after lock nut is torqued. It is common for clearance to change slightly during lock nut tightening.
   Torque spec

   Valve Lash Adjusting Screw Lock Nut20 Nm (15 lb-ft)
9. 9

   Verify all valve adjustments
   Rotate crankshaft through two complete revolutions by hand. Recheck valve lash on all 20 valves (10 cylinders, 2 valves each) to confirm proper clearance. Readjust any valves that are out of specification. This verification step prevents comeback issues from loose lock nuts or incorrect initial adjustment.
10. 10

    Clean gasket surfaces
    Remove old gasket material from valve covers and cylinder head gasket surfaces using plastic gasket scraper. Do not use metal scrapers that can gouge aluminum surfaces. Clean surfaces with parts cleaner and shop towels. Ensure all oil, debris, and old gasket material are completely removed. Inspect valve cover gasket surfaces for warping or damage.
    ⚠Aluminum surfaces scratch easily. Use only plastic scrapers and avoid abrasive pads on sealing surfaces.
11. 11

    Install new valve cover gaskets
    Install new valve cover gaskets onto valve covers. Ensure gaskets are properly seated in valve cover grooves. Replace valve cover bolt grommets. Do not use excessive RTV sealant - these gaskets seal properly without additional sealant when torqued correctly. If minor seepage has occurred at intake manifold/cylinder head junction, apply small bead of RTV to those corners only.
12. 12

    Install valve covers
    Position valve covers onto cylinder heads, aligning bolt holes. Install valve cover bolts with grommets. Start all bolts by hand before tightening any. Torque valve cover bolts in sequence from center outward, alternating side-to-side in a circular pattern. Final torque to specification.
    ⚠Over-tightening valve cover bolts will distort covers and cause oil leaks. Use torque wrench and follow sequence.
    Torque spec

    Cover Bolts16 Nm (12 lb-ft)
13. 13

    Reinstall ignition components
    Reinstall spark plug wire retaining clips to valve covers. Connect spark plug wires to correct cylinder positions using labels from step 2. Reconnect any ignition coil connectors. Verify all wires are fully seated on spark plugs with positive click.
14. 14

    Reinstall air intake system
    Reconnect all vacuum lines and breather hoses to valve covers. Reinstall air filter housing and intake ductwork. Connect intake tube to throttle body and secure all clamps. Verify all connections are tight and properly routed.
15. 15

    Final inspection and test
    Reconnect negative battery cable. Install engine covers if equipped. Start engine and listen for abnormal valve train noise. Allow engine to idle for 2-3 minutes while checking for oil leaks around valve covers. Normal slight ticking sound from valve train is expected with properly adjusted mechanical lifters. Shut off engine and recheck valve cover bolt torque after engine reaches operating temperature and cools.

Reassembly

1. Valve cover bolt torque should be rechecked after first heat cycle
2. Minor valve train noise is normal with mechanical adjustment - loud ticking or tapping indicates incorrect adjustment
3. Valve lash should be rechecked every 30,000 miles or if valve train noise develops

Verification

• Engine starts normally and idles smoothly without excessive valve train noise
• No oil leaks present around valve cover gaskets after 5-10 minute idle period
• Valve lash on all 20 valves measures 0.012" with feeler gauge after adjustment
• Engine produces normal power and throttle response during test drive

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