Head Gasket - Single

Replace the cylinder head gasket on one bank of the 390ci V8 engine, including removal and reinstallation of the cylinder head, valvetrain components, and associated hardware.

Warnings

Tools required

Parts

• Cylinder head gasket (single) × 1 — Use OEM specification for AMC 390
• Intake manifold gasket set × 1 — AMC 390 intake gasket set
• Exhaust manifold gaskets × 1 — AMC 390 exhaust gaskets
• Valve cover gasket × 1 — AMC 390 valve cover
• Cylinder head bolt set × 1 — Recommend replacement on high-mileage engines
• Pushrod guide plate × 1 — If equipped and damaged
• Engine coolant × 1 — Ethylene glycol antifreeze

Fluids

• Engine coolant (50/50 mix) — 6 qt
• Engine oil — 5 qt

Preparation

1. Disconnect negative battery cable
2. Drain engine coolant completely into appropriate container
3. Remove air cleaner assembly and label all vacuum hoses for reinstallation
4. Label and photograph all electrical connections, fuel lines, and linkages before disconnection
5. Allow engine to reach ambient temperature before beginning disassembly

Procedure

1. 1

   Remove valve cover and accessories
   Remove the valve cover from the affected cylinder bank. Remove any accessory brackets, alternator mounts, or air conditioning components that interfere with head removal. On the driver side, power steering pump may need to be unbolted and moved aside without disconnecting hoses.
2. 2

   Disconnect intake manifold
   Remove carburetor linkage and fuel line. Unbolt intake manifold from the cylinder head being serviced. The intake manifold spans both heads, so you may need to loosen bolts on both sides and lift it enough to access head bolts, or remove it completely. Label all vacuum ports and electrical connections.
   ⚠Fuel may spill from carburetor and lines. Have rags ready and ensure adequate ventilation.
3. 3

   Remove exhaust manifold
   Disconnect exhaust pipe from manifold at the flange. Remove all exhaust manifold bolts and remove the manifold from the cylinder head. Apply penetrating oil to studs if they are rusted. The Machine uses dual exhaust, so identify which side you are working on.
   ⚠Exhaust manifold studs may be seized or brittle. Use penetrating oil and allow time to soak before attempting removal to prevent breakage.
4. 4

   Remove rocker arm assembly
   Loosen rocker arm shaft bolts evenly in reverse order of tightening sequence. Remove the rocker arm shaft assembly as a complete unit. The AMC 390 uses a shaft-mounted rocker system. Keep the assembly together if not rebuilding, or mark each rocker and shaft position if disassembling.
5. 5

   Remove pushrods
   Lift out all pushrods and store them in order. Use a numbered holder or mark them 1-8 corresponding to their cylinder positions. Inspect each pushrod by rolling on a flat surface to check for bending. Check ends for wear patterns.
   ⚠Pushrods must be reinstalled in their original positions to maintain wear patterns. Mixing positions can cause valvetrain noise and premature wear.
6. 6

   Remove cylinder head bolts
   Remove all cylinder head bolts in reverse of the tightening sequence, working from the outer bolts toward the center. There are typically 10 head bolts on each head of the AMC 390. Use a breaker bar if necessary, then switch to a ratchet. Keep bolts in order if reusing.
7. 7

   Remove cylinder head
   Carefully lift the cylinder head straight up off the engine block. The head is heavy (approximately 50-60 lbs), so use proper lifting technique or get assistance. If the head is stuck, gently tap with a rubber mallet on a corner casting - never pry between the gasket surfaces.
   ⚠Cylinder head weighs approximately 50-60 pounds. Use proper lifting technique and get assistance to avoid injury or dropping the head.
8. 8

   Clean gasket surfaces
   Remove all old gasket material from both the cylinder head and engine block deck surfaces using a gasket scraper. Be extremely careful not to gouge the aluminum or cast iron surfaces. Follow with a wire brush and solvent. Stuff clean rags into cylinder bores to prevent debris from entering. Vacuum all debris thoroughly.
   ⚠Do not allow gasket material or debris to fall into cylinder bores, oil passages, or coolant passages. This can cause severe engine damage upon startup.
9. 9

   Inspect cylinder head and block surfaces
   Use a precision straight edge and feeler gauge to check the cylinder head deck surface for warping. Check lengthwise, widthwise, and diagonally. Maximum allowable warpage is typically 0.003" for the AMC 390. Also check the block deck surface. If warpage exceeds specification, the head must be resurfaced at a machine shop.
10. 10

    Install new head gasket
    Position the new head gasket on the engine block, ensuring proper orientation. Most gaskets have "FRONT" or "TOP" markings. Align all bolt holes and coolant passages. Do not use sealant on modern composite head gaskets unless specifically required by gasket manufacturer.
11. 11

    Install cylinder head
    Carefully lower the cylinder head onto the block, aligning it with the dowel pins and head gasket. Ensure the gasket does not shift during installation. Guide the head straight down without sliding it on the gasket surface.
12. 12

    Install and torque head bolts
    Install all cylinder head bolts finger-tight. Using a torque wrench, tighten bolts in the proper sequence (center outward pattern) in three stages: first to 1/3 final torque, then 2/3, then final torque. AMC 390 head bolts typically require 100-105 ft-lbs final torque, but verify with factory specifications. Some rebuilds may use newer bolts with different specs.
    ℹ️Without factory torque specifications provided, consult an AMC service manual or reputable source for exact torque values and tightening sequence. Typical specification is 100-105 ft-lbs in proper sequence.
13. 13

    Reinstall pushrods and rocker assembly
    Install each pushrod in its original position, ensuring the lower end seats properly in the lifter cup. Install the rocker arm shaft assembly, ensuring rocker arms align with pushrods and valve stems. Tighten rocker shaft bolts evenly in correct sequence to specification (typically 19-25 ft-lbs for AMC rocker shafts).
14. 14

    Reinstall exhaust and intake manifolds
    Install new exhaust manifold gaskets and bolt the exhaust manifold to the head. Reconnect exhaust pipe. Install new intake manifold gaskets (both sides if manifold was fully removed) and install intake manifold, torquing bolts in proper sequence from center outward. Typical intake manifold torque is 25-30 ft-lbs for AMC 390.
15. 15

    Complete reassembly
    Install new valve cover gasket and reinstall valve cover. Reinstall all accessories, brackets, alternator, power steering pump, and air conditioning components. Reconnect all vacuum lines, electrical connections, and fuel lines per your labels and photos. Install air cleaner assembly.

Reassembly

1. Refill cooling system with fresh 50/50 coolant mix, burping system to remove air pockets
2. Check engine oil level and top off or change oil if contaminated with coolant
3. Reconnect negative battery cable
4. Double-check all fasteners, connections, and hose clamps before starting engine

Verification

• Start engine and listen for unusual noises, particularly valvetrain noise indicating improper pushrod or rocker installation
• Check for coolant leaks around head gasket, intake manifold, and hose connections
• Check for exhaust leaks at manifold and pipe connection
• Monitor engine temperature to ensure proper cooling system function
• Allow engine to reach operating temperature, shut off, allow to cool, then recheck head bolt torque after first heat cycle (recommended)
• Check for oil leaks at valve cover after test drive
• Verify smooth idle and proper engine performance under load

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