Cylinder Head R&R

Remove and replace cylinder heads on the AMC 390ci V8 engine, including disassembly of valvetrain components and cleaning of mating surfaces.

Warnings

Tools required

Parts

• Cylinder head gaskets (left and right) × 2 — AMC 390 V8 specific
• Intake manifold gasket set × 1 — Use OEM specification
• Exhaust manifold gaskets × 2 — Use OEM specification
• Valve cover gaskets × 2 — AMC 390 V8
• Cylinder head bolts (if reuse not recommended) × 1 — Use OEM specification
• Intake manifold bolts/hardware × 1 — As needed
• Exhaust manifold hardware × 1 — As needed
• Spark plugs × 8 — Use OEM specification
• Engine coolant × 1 — Ethylene glycol based
• Pushrod guide plates (if applicable) × 1 — AMC 390 V8

Fluids

• Engine coolant (50/50 mix) — 16 qt

Preparation

1. Disconnect negative battery cable
2. Drain cooling system completely by opening radiator petcock and block drain plugs
3. Remove air cleaner assembly and label all vacuum hoses for reinstallation
4. Remove carburetor or throttle linkage to provide clearance
5. Label and photograph spark plug wire routing, then disconnect wires from all spark plugs
6. Place shop towels in valley area to prevent debris from entering engine

Procedure

1. 1

   Remove valve covers and accessories
   Remove both valve covers by unbolting hold-down bolts. Remove any brackets, wiring harnesses, or accessory components attached to cylinder heads including alternator brackets, power steering pump brackets, and air injection components if equipped. Tag all hardware for proper reinstallation.
2. 2

   Disconnect intake and exhaust manifolds
   Remove intake manifold by disconnecting all coolant hoses, fuel lines, and vacuum lines first. Unbolt intake manifold using proper sequence (outside bolts first, working inward). Disconnect exhaust pipes from exhaust manifolds at the flange connections. Remove exhaust manifolds from cylinder heads if necessary for access or if head service is required.
3. 3

   Remove rocker arm assemblies
   On the AMC 390, remove the rocker arm shaft assembly by unbolting the shaft support bolts evenly. Keep rocker arms in order by cylinder position. If equipped with individual rocker arms and studs, loosen rocker arm nuts and pivot rockers away from pushrods. Store all components organized by cylinder number.
4. 4

   Remove pushrods
   Lift out all pushrods and place them in a numbered holder or cardboard template to maintain their original positions. Inspect each pushrod for straightness by rolling on a flat surface. Mark any bent pushrods for replacement. Clean pushrods thoroughly if reusing.
5. 5

   Remove spark plugs
   Remove all eight spark plugs using a spark plug socket. This reduces compression and allows easier cylinder head removal, and prevents damage to spark plugs during head removal.
6. 6

   Remove cylinder head bolts
   Using a breaker bar and appropriate socket, loosen cylinder head bolts in the reverse order of the tightening sequence (outside bolts first, working toward center). AMC typically uses a spiral pattern from the ends toward the center. Loosen bolts in stages, 1/4 turn at a time to prevent head warpage. Remove all head bolts and store them in order if reusing.
7. 7

   Remove cylinder heads
   Carefully lift cylinder heads straight up off the engine block. The heads are heavy (approximately 50-60 lbs each) and may require assistance. If head is stuck, tap gently with a rubber mallet on a reinforced area only. Never pry between head and block surfaces. Remove and discard old head gaskets.
8. 8

   Clean mating surfaces
   Using a plastic or brass gasket scraper, carefully remove all old gasket material from cylinder head and block mating surfaces. Do not gouge or scratch surfaces. Clean surfaces with solvent and wipe dry with lint-free rags. Stuff clean rags into cylinder bores to prevent debris from entering.
9. 9

   Inspect surfaces for warpage
   Place a precision straight edge across the cylinder head mating surface in multiple directions (lengthwise, diagonally, and across). Use feeler gauges to check for warpage. AMC 390 cylinder heads should not exceed 0.007 inch warpage. If beyond specification, heads must be resurfaced by a machine shop. Also inspect for cracks, especially between valve seats and in combustion chambers.
10. 10

    Prepare for reassembly
    If cylinder heads were serviced (valve job, resurfacing), ensure all machining debris is cleaned. Check that all new gaskets match old gaskets exactly for coolant and oil passage alignment. Verify cylinder head bolt threads in block are clean and free of coolant or oil - chase threads with appropriate tap if necessary. Apply light oil to bolt threads unless using thread sealant per specifications.
11. 11

    Install new head gaskets and cylinder heads
    Remove rags from cylinder bores. Position new head gaskets on block, ensuring correct orientation - gaskets are marked for front and for left/right side. Align gasket locating dowels. Carefully lower cylinder heads onto block, ensuring gasket stays in position. Install all head bolts finger-tight.
12. 12

    Torque cylinder head bolts
    Torque cylinder head bolts in three stages using proper sequence (center bolts first, spiraling outward): First pass to 50 ft-lbs, second pass to 75 ft-lbs, final pass to manufacturer specification (typically 100-105 ft-lbs for AMC 390). Consult factory service manual for exact torque value and sequence. Allow engine to sit for 30 minutes, then re-torque to final specification. Note: Some rebuilders recommend re-torquing after initial heat cycle.
13. 13

    Reinstall pushrods and rocker assemblies
    Install pushrods in their original positions, ensuring they are seated properly in lifter cups. Rotate engine by hand to ensure all lifters are on base circle of camshaft. Install rocker arm shaft assembly or individual rocker arms. Adjust valve lash according to factory specifications (typically 0.012-0.014 inch on AMC 390 hydraulic lifters when cold, or zero lash preload method).
14. 14

    Reinstall manifolds and accessories
    Install exhaust manifolds with new gaskets if removed. Install intake manifold with new gaskets using proper torque sequence (center bolts first, working outward in stages). Reinstall all brackets, accessories, and wiring harnesses. Reconnect all coolant hoses, vacuum lines, and fuel lines. Install valve covers with new gaskets.
15. 15

    Final assembly and fill fluids
    Install new spark plugs torqued to specification. Reconnect spark plug wires per original routing. Reinstall carburetor linkage and air cleaner. Fill cooling system with proper coolant mixture. Reconnect battery cable. Before starting, rotate engine by hand two full revolutions to verify no interference and proper valve operation.

Reassembly

1. Double-check all bolts are torqued to specification, especially cylinder head bolts and intake manifold bolts
2. Verify all vacuum lines, coolant hoses, and electrical connections are properly reinstalled
3. Ensure valve covers are properly sealed to prevent oil leaks
4. Check that all accessories and brackets are securely mounted

Verification

• Start engine and listen for unusual noises, ticking, or knocking that might indicate improper valve adjustment or installation
• Allow engine to reach operating temperature and check for coolant, oil, or exhaust leaks around cylinder heads and manifolds
• Monitor coolant level as air purges from system; top off as necessary
• After initial heat cycle (engine fully warmed and cooled), consider re-checking cylinder head bolt torque per manufacturer recommendation
• Test drive vehicle and verify normal operation, power delivery, and absence of misfires
• Recheck all fluid levels and inspect for leaks after 100-mile break-in period

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