Valve Seals

Replace valve stem seals on the 390ci V8 engine to eliminate oil consumption and smoking issues without removing the cylinder heads.

Warnings

Tools required

Parts

• Valve stem seal set (16 seals) × 1 — Use OEM specification for 390ci V8
• Valve cover gasket set × 1 — Use OEM specification
• Timing cover gasket × 1 — Use OEM specification
• Crankshaft front seal × 1 — Use OEM specification
• Intake manifold gasket set × 1 — Use OEM specification

Fluids

• Engine oil (10W-30 or 10W-40) — 5 qt
• Engine coolant (ethylene glycol) — 4 qt

Preparation

1. Disconnect negative battery cable
2. Drain engine coolant into suitable container
3. Drain engine oil and remove oil filter
4. Remove air cleaner assembly and label all vacuum lines
5. Remove distributor cap and mark rotor position relative to distributor body and engine block
6. Label and disconnect all spark plug wires, then remove spark plugs
7. Remove radiator upper hose
8. Position number 1 cylinder at TDC on compression stroke by rotating crankshaft clockwise until timing marks align and rotor points to number 1 cylinder
9. Place shop towels in valley area to catch any dropped parts

Procedure

1. 1

   Remove valve covers
   Remove valve cover bolts from both driver and passenger side valve covers. Carefully pry covers loose if stuck, taking care not to damage mating surfaces. Remove valve covers and old gaskets. Clean all gasket material from valve cover and cylinder head mating surfaces using gasket scraper.
2. 2

   Remove intake manifold
   Label and disconnect all vacuum lines, electrical connections, and throttle linkage from carburetor. Remove carburetor mounting nuts and lift carburetor away. Unbolt intake manifold using proper sequence (working from center outward). Carefully lift intake manifold straight up to avoid damaging gaskets. Cover intake ports with clean shop rags to prevent debris entry.
3. 3

   Remove timing cover
   Remove fan shroud if equipped, then remove fan blades and water pump pulley. Remove drive belts. Using harmonic balancer puller, remove harmonic balancer from crankshaft. Remove timing cover bolts and carefully pry timing cover away from engine block. Note position of timing marks on crankshaft and camshaft sprockets before proceeding.
4. 4

   Identify valve train layout
   With timing marks aligned at TDC on number 1 cylinder, identify which valves are closed (springs under tension). On the 390ci V8, valves are arranged in pairs along each head. Make notes or take photos of rocker arm positions for reference.
5. 5

   Remove rocker arms for first cylinder pair
   Starting with cylinder number 1, loosen rocker arm pivot bolts and remove rocker arms from both intake and exhaust valves. Keep rocker arms organized by position for reinstallation. Remove pushrods and store vertically in order.
6. 6

   Install air pressure adapter and pressurize cylinder
   Thread air pressure adapter into number 1 spark plug hole. Connect air compressor line and apply 90-100 PSI of air pressure to hold valves in closed position. Listen for air leaking from other cylinders or exhaust, which would indicate piston not at proper TDC position.
7. 7

   Compress valve springs and remove keepers
   Position valve spring compressor tool on first valve assembly. Compress spring just enough to relieve pressure on valve keepers. Using needle nose pliers or magnetic tool, carefully remove both valve keepers. Slowly release spring compressor and remove retainer and spring. Repeat for second valve on this cylinder.
8. 8

   Remove old valve seals
   Using pliers, carefully pull old valve stem seal off valve guide. Inspect valve stem for grooves or damage. Clean valve stem and guide area thoroughly with shop rag. Repeat for all valves on this cylinder.
9. 9

   Install new valve seals
   Lightly oil new valve stem seal inside diameter. Carefully slide new seal down valve stem and press firmly onto valve guide until fully seated. Use socket or seal installation tool to ensure seal is properly seated without cocking. Verify seal is secure and sits flush on guide.
10. 10

    Reinstall valve springs and keepers
    Place valve spring and retainer back over valve stem. Using valve spring compressor, compress spring enough to install valve keepers. Carefully position both keepers in valve stem groove, ensuring they seat properly. Slowly release compressor while watching that keepers remain engaged. Tap valve stem tip lightly with plastic hammer to ensure keepers are fully seated.
11. 11

    Repeat for remaining cylinders
    Release air pressure and move to next cylinder pair. Rotate crankshaft clockwise to bring next cylinder to TDC on compression stroke (90 degrees of rotation for V8). Verify valve positions before removing rocker arms. Repeat steps 5-10 for all remaining cylinders, working through firing order: 1-8-4-3-6-5-7-2.
12. 12

    Reinstall rocker arms and adjust valves
    Reinstall pushrods in original positions. Install rocker arms and pivot bolts. With cylinder at TDC compression stroke, adjust valve lash according to AMC specifications (typically zero lash plus 1/2 to 1 full turn for hydraulic lifters). Rotate engine and adjust remaining valves following proper sequence.
13. 13

    Reinstall timing cover
    Install new crankshaft front seal in timing cover. Apply thin bead of RTV sealant to timing cover gasket mating surfaces. Position new gasket and install timing cover, ensuring oil slinger is in place. Install and tighten timing cover bolts in crisscross pattern. Reinstall harmonic balancer, water pump pulley, and drive belts.
14. 14

    Reinstall intake manifold
    Remove shop rags from intake ports. Install new intake manifold gaskets with proper orientation. Apply thin bead of RTV at front and rear block corners where gaskets meet. Carefully lower intake manifold into position. Install bolts and tighten in proper sequence from center outward in three stages to ensure even gasket compression.
15. 15

    Reinstall valve covers and final components
    Install new valve cover gaskets and reinstall valve covers with even torque on all bolts. Reinstall carburetor with new gasket. Reconnect all vacuum lines, electrical connections, and throttle linkage per original markings. Install spark plugs and reconnect wires according to firing order markings. Reinstall distributor cap and air cleaner assembly.

Reassembly

1. Refill engine with fresh engine oil and new oil filter
2. Refill cooling system with proper coolant mixture
3. Reconnect negative battery cable
4. Double-check all electrical connections, vacuum lines, and hose clamps
5. Verify all bolts are properly torqued and no tools remain in engine bay

Verification

• Start engine and check for oil leaks around valve covers and intake manifold
• Check for coolant leaks around timing cover and water pump
• Listen for unusual valve train noise indicating improper valve adjustment
• Allow engine to reach operating temperature and verify no oil smoke from exhaust during acceleration
• Check oil level after initial run and top off if necessary
• Monitor oil consumption over next 500 miles to verify seal replacement success
• Verify timing marks are still properly aligned if timing cover was disturbed
• Check ignition timing with timing light and adjust distributor if necessary

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