Head Gaskets - Both

Complete removal and replacement of both cylinder head gaskets on the AMC 390ci V8 engine, including disassembly of intake/exhaust manifolds, valve train components, and cylinder heads.

Warnings

Tools required

Parts

• Cylinder head gasket set × 1 — Use OEM specification or Fel-Pro HS7733PT
• Intake manifold gasket set × 1 — Use OEM specification
• Exhaust manifold gaskets × 2 — Use OEM specification
• Valve cover gaskets × 2 — Use OEM specification
• Cylinder head bolts × 1 — Use OEM specification, recommend replacement
• Intake manifold bolts/hardware × 1 — As needed
• Exhaust manifold hardware × 1 — As needed
• Valve stem seals × 16 — Use OEM specification
• Water pump gasket × 1 — Use OEM specification
• Thermostat housing gasket × 1 — Use OEM specification
• RTV silicone sealant × 1 — High-temperature rated

Fluids

• Engine coolant (50/50 mix) — 16 qt
• Engine oil — 5 qt
• Penetrating oil — 1 qt

Preparation

1. Park vehicle on level surface and allow engine to cool completely (minimum 4 hours)
2. Disconnect negative battery cable
3. Drain engine coolant by removing radiator petcock and lower radiator hose
4. Drain engine oil and remove oil filter
5. Remove air cleaner assembly and breather
6. Label and disconnect all vacuum lines from intake manifold and carburetor
7. Tag and remove spark plug wires, then remove all spark plugs
8. Remove distributor cap and mark distributor position relative to block before removal
9. Disconnect fuel line at fuel pump (be prepared for residual fuel spillage)
10. Disconnect throttle linkage and transmission kickdown linkage from carburetor
11. Remove alternator, power steering pump (if equipped), and A/C compressor (if equipped) - set aside without disconnecting hoses
12. Remove radiator upper hose and heater hoses from intake manifold

Procedure

1. 1

   Remove valve covers
   Remove valve cover bolts from both sides. Tap valve covers gently with rubber mallet if stuck. Remove valve covers and set aside with gaskets. Clean any oil residue from valve train area with shop towels.
2. 2

   Remove intake manifold
   Remove carburetor from intake manifold. Unbolt intake manifold using proper sequence (work from center outward). Carefully lift intake manifold straight up to avoid damaging gasket surfaces. Remove and discard intake manifold gaskets. Stuff clean shop rags into intake ports on cylinder heads to prevent debris entry.
3. 3

   Remove exhaust manifolds
   Apply penetrating oil to all exhaust manifold bolts and studs and allow to soak for at least 30 minutes. Disconnect exhaust pipes from manifolds at flange connections. Remove exhaust manifold bolts working from outside toward center. Carefully remove both exhaust manifolds. Inspect studs for damage - replace any damaged or seized studs.
4. 4

   Remove rocker arm assemblies
   Loosen rocker arm shaft bolts evenly in multiple passes to avoid bending shafts. Remove rocker arm shaft assemblies as complete units. Keep assemblies separated by side (left/right). Remove pushrods and place in order in numbered holder or cardboard template. Each pushrod must return to its original location.
5. 5

   Remove cylinder head bolts
   Remove cylinder head bolts in reverse order of tightening sequence (work from outside toward center). AMC 390 uses 10 head bolts per side. Keep bolts organized by position. Note any bolts that are different lengths - they must return to their original positions.
6. 6

   Remove cylinder heads
   Break cylinder heads loose by gently prying at designated pry points (near front corners). Never pry between head and block gasket surfaces. Lift cylinder heads straight up with assistance - they weigh approximately 50 pounds each. Place heads on wood blocks with combustion chambers facing up.
7. 7

   Clean and inspect surfaces
   Remove old head gaskets from block deck. Use gasket scraper to clean all gasket material from cylinder head and block deck surfaces. Be careful not to gouge aluminum or cast iron surfaces. Clean intake and exhaust manifold mating surfaces. Use solvent and wire brush to clean all bolt holes in block. Blow out bolt holes with compressed air to remove any coolant or oil. Inspect for cracks in combustion chambers, between valve seats, and around water passages.
8. 8

   Check deck surface flatness
   Using straight edge and feeler gauges, check cylinder head and block deck surfaces for warpage. Place straight edge across multiple positions (front-to-back, side-to-side, and diagonally). Maximum allowable warpage is 0.003 inches in any 6-inch span, 0.006 inches overall. If beyond specification, heads must be professionally resurfaced. Check block deck similarly.
9. 9

   Prepare cylinder heads for installation
   Have cylinder heads professionally cleaned, inspected, and resurfaced if necessary. Replace valve stem seals while heads are off. Check valve springs for proper tension. Perform valve lapping if needed. Verify all coolant and oil passages are clear. Do not install heads until you are certain they are within specification and ready for service.
10. 10

    Install new head gaskets and cylinder heads
    Ensure block deck and head surfaces are perfectly clean and dry. Install new head gaskets on block with all holes properly aligned. Do not use any sealer on head gaskets. Note orientation markings (TOP or FRONT) on gaskets. Carefully position cylinder heads onto block, aligning dowel pins. Install new cylinder head bolts with light coating of engine oil on threads and under bolt heads. Hand-tighten all bolts first.
11. 11

    Torque cylinder head bolts
    Torque cylinder head bolts in proper sequence (start at center, work outward in spiral pattern) in three stages: First pass to 50 ft-lbs, second pass to 75 ft-lbs, final pass to 95-100 ft-lbs. Follow factory torque sequence diagram. After engine reaches operating temperature for first time, allow to cool and re-torque heads to final specification (cold retorque recommended by AMC).
    ⚠Without factory torque specifications verified, use 95-100 ft-lbs as final torque for AMC 390 head bolts. Consult AMC service manual for exact specifications and sequence.
12. 12

    Install pushrods and rocker assemblies
    Install pushrods in their original positions, ensuring each seats properly in lifter socket. Apply assembly lube to pushrod tips and rocker arm contact points. Install rocker arm shaft assemblies. Tighten rocker shaft bolts evenly in multiple passes to 20-25 ft-lbs. Rotate engine two full revolutions by hand to verify no valve-to-piston contact.
13. 13

    Install exhaust manifolds
    Install new exhaust manifold gaskets. Position exhaust manifolds and install bolts with anti-seize compound on threads. Tighten manifold bolts evenly working from center outward to 25-30 ft-lbs. Reconnect exhaust pipes to manifold flanges with new gaskets.
14. 14

    Install intake manifold
    Remove shop rags from intake ports. Apply thin bead of RTV silicone to block where intake manifold contacts at front and rear (china wall areas). Position new intake manifold gaskets. Carefully lower intake manifold into position, ensuring gaskets stay aligned. Install intake bolts and tighten from center outward in crisscross pattern to 35-40 ft-lbs. Install carburetor with new gasket.
15. 15

    Final reassembly
    Install valve covers with new gaskets, tighten bolts to 5-7 ft-lbs. Install distributor in original marked position. Reconnect all vacuum lines, fuel line, throttle linkage, and electrical connections. Install spark plugs and tighten to 25-30 ft-lbs. Reinstall spark plug wires in proper firing order (1-8-4-3-6-5-7-2). Reinstall alternator, power steering pump, and A/C compressor. Connect all drive belts and adjust tension. Install air cleaner assembly.

Reassembly

1. Fill cooling system with fresh 50/50 coolant mix, burp system of air pockets
2. Fill engine with fresh oil and new filter
3. Double-check all fasteners for proper torque
4. Verify all electrical connections, vacuum lines, and fuel lines are properly reconnected
5. Check drive belt tensions
6. Reconnect negative battery cable

Verification

• Start engine and check immediately for coolant, oil, or exhaust leaks
• Allow engine to reach operating temperature while monitoring for leaks and unusual noises
• Check for proper oil pressure on gauge
• Verify cooling system is maintaining proper temperature
• Listen for valve train noise - should be minimal with proper adjustment
• After initial warm-up and cool-down cycle, perform cold retorque of cylinder head bolts to specification
• Recheck all fluid levels after test drive
• Monitor for any coolant consumption or oil contamination over first 100 miles

More procedures for this vehicle