Piston Rings - All

Complete removal and replacement of piston rings on all eight cylinders of the 390ci V8 engine, requiring removal of the engine, cylinder heads, pistons, and inspection of cylinder walls.

Warnings

Tools required

Parts

• Piston ring set (standard or oversize as needed) × 1 — AMC 390 V8 piston ring set - verify size
• Head gasket set × 1 — AMC 390 V8 head gasket set
• Intake manifold gasket set × 1 — AMC 390 V8 intake gasket set
• Exhaust manifold gaskets × 2 — AMC 390 V8 exhaust gaskets
• Oil pan gasket × 1 — AMC 390 V8 oil pan gasket
• Rear main seal × 1 — AMC 390 V8 rear main seal
• Rod bearing set (if replacement needed) × 1 — AMC 390 V8 connecting rod bearings
• Valve cover gaskets × 2 — AMC 390 V8 valve cover gaskets
• Engine oil and filter × 1 — 5W-30 or 10W-30 engine oil
• Anti-seize compound × 1 — Use OEM specification
• Engine assembly lube × 1 — Use OEM specification

Fluids

• Engine oil — 5 qt
• Engine coolant — 16 qt

Preparation

1. Park vehicle on level surface and disconnect negative battery cable
2. Drain engine oil and coolant into appropriate containers
3. Remove hood and label all hinge bolt positions for reinstallation
4. Remove air cleaner assembly and carburetor linkage
5. Disconnect all electrical connections from engine (alternator, starter, temperature sender, oil pressure sender, distributor)
6. Label and disconnect all vacuum lines from engine
7. Remove radiator, fan, fan shroud, and all cooling system hoses
8. Disconnect fuel lines from fuel pump and carburetor
9. Remove exhaust manifolds or disconnect exhaust pipes at manifold flanges
10. Remove transmission bellhousing bolts (if removing engine separately from transmission)
11. Support transmission with jack if separating from engine
12. Remove motor mount bolts from frame brackets
13. Gather clean workspace and parts storage containers for keeping components organized by cylinder number

Procedure

1. 1

   Remove engine from vehicle
   Attach engine hoist to intake manifold using appropriate lifting brackets or chains. Ensure lifting points are balanced. Carefully lift engine while guiding it clear of engine bay. Monitor clearance around firewall, fender wells, and steering components. Once clear, transfer engine to engine stand and secure using bellhousing bolt holes.
2. 2

   Remove external engine components
   With engine on stand, remove intake manifold, carburetor (if not already removed), valve covers, distributor, fuel pump, water pump, timing chain cover, and oil pan. Remove oil pickup tube. Mark distributor position before removal for reinstallation reference. Keep all fasteners organized by component.
3. 3

   Remove cylinder heads
   Remove rocker arm assemblies, pushrods, and cylinder head bolts following proper sequence (work from outer bolts toward center). Lift cylinder heads off engine block. Store pushrods in order so they can be reinstalled in original positions. Keep head bolts with corresponding head.
   ⚠Cylinder heads are heavy (approximately 50 lbs each). Use proper lifting technique or get assistance.
4. 4

   Remove cylinder ridge and prepare for piston removal
   Rotate crankshaft to bring piston to bottom dead center. Use ridge reamer to carefully remove ridge at top of each cylinder bore. The ridge must be completely removed to prevent ring land breakage during piston removal. Clean away all cutting debris with shop towels. Repeat for all eight cylinders.
   ⚠Ridge reamer can damage cylinder wall if used improperly. Follow tool manufacturer instructions and do not cut below the ridge into the main cylinder bore.
5. 5

   Mark and remove connecting rod caps
   Identify and mark each connecting rod and cap with corresponding cylinder number (1-8) using number stamps or permanent marker. Verify rod and cap match marks align. Remove rod cap nuts and carefully remove caps, keeping them with their respective rods. Install rod cap bolts back into rods finger-tight to prevent thread damage.
6. 6

   Remove pistons from cylinders
   Push each piston and rod assembly up and out through top of cylinder bore using wooden dowel or hammer handle on rod bolt heads. Avoid scratching cylinder walls or crankshaft journals. Immediately reinstall correct rod cap on each rod. Store piston assemblies in order in parts organizer labeled 1-8.
7. 7

   Measure cylinder bore condition
   Using dial bore gauge or inside micrometer, measure each cylinder bore at top, middle, and bottom positions in both parallel and perpendicular orientations to crankshaft. Calculate taper (difference between top and bottom readings) and out-of-round (difference between parallel and perpendicular readings). Record all measurements. Maximum acceptable taper is 0.006 inch, maximum out-of-round is 0.003 inch. Cylinders exceeding these specifications require boring and oversize pistons.
   ℹ️If any cylinder exceeds wear limits, this procedure cannot continue without machine shop services for boring and honing to next oversize.
8. 8

   Remove old piston rings
   Using piston ring expander tool, carefully expand and remove each ring from piston. Remove top compression ring first, then second compression ring, then oil control ring assembly. Inspect ring grooves for cracks, excessive wear, or damage. Clean ring grooves thoroughly using piston ring groove cleaner or broken ring piece, removing all carbon deposits.
9. 9

   Inspect pistons and connecting rods
   Examine each piston for cracks, scoring, or damaged ring lands. Measure piston diameter at skirt area perpendicular to wrist pin using micrometer. Check connecting rod bearings for wear, scoring, or damage. If bearings show wear, measure crankshaft rod journals and replace bearings as necessary. Inspect rod bolts for stretching or damage.
10. 10

    Deglaze cylinder walls
    Using cylinder hone with 280-320 grit stones, deglaze each cylinder bore with up-and-down motion while rotating hone. Maintain 30-degree crosshatch pattern. Hone just enough to break the glaze and create proper surface for ring seating (approximately 30-60 seconds per cylinder). Thoroughly clean cylinders with hot soapy water, then wipe with clean white cloth until no residue appears. Dry immediately and coat with clean engine oil to prevent rust.
    ⚠Over-honing will remove excessive material and increase cylinder bore size. Hone only until glaze is removed and proper crosshatch pattern appears.
11. 11

    Check new piston ring end gap
    For each cylinder, place new top compression ring into cylinder bore and use inverted piston to push ring down approximately 1 inch to square it in bore. Measure end gap with feeler gauge. Specification for AMC 390 is typically 0.010-0.020 inch for compression rings, 0.015-0.055 inch for oil rings. Repeat for all rings in all cylinders. If gap is too tight, carefully file ring ends. Record measurements to ensure proper ring-to-cylinder match during installation.
12. 12

    Install new piston rings
    Using piston ring expander tool, install rings on each piston in order: oil control ring expander first, then oil control rails, then lower compression ring (marked side up), then upper compression ring (marked side up). Verify all rings rotate freely in their grooves. Stagger ring end gaps 120 degrees apart, ensuring no gaps align with wrist pin direction. Oil control ring rail gaps should be opposite each other.
    ⚠Rings are brittle and will break if over-expanded. Use proper ring expander tool and expand only enough to clear piston diameter.
13. 13

    Install pistons into cylinders
    Generously coat cylinder walls, piston skirts, and rings with engine assembly lube. Ensure rod bearings are in place and properly lubricated. Rotate crankshaft to position rod journal at bottom dead center for cylinder being worked. Using piston ring compressor, compress rings on piston and orient piston with directional marking (usually notch or arrow) toward front of engine. Gently tap piston into cylinder bore with wooden hammer handle while guiding connecting rod over journal. Ensure rings enter bore squarely to prevent breakage. Install rod cap in correct orientation and install nuts finger-tight. Repeat for all eight pistons in numerical order.
14. 14

    Torque connecting rod caps and verify bearing clearance
    Before final torquing, install Plastigage on each rod journal to verify bearing clearance. Torque rod cap nuts to specification (typically 45-50 ft-lbs for AMC 390, but verify with service manual as torque specs not provided). Remove cap and measure Plastigage width. Proper clearance is 0.0008-0.0028 inch. If clearance is correct, apply engine assembly lube to bearings, reinstall caps, and torque to specification in smooth motion. Verify crankshaft rotates freely after each rod is torqued.
    ⚠Do not rotate crankshaft with Plastigage installed as this will give false readings. Remove cap immediately after torquing to check clearance.
15. 15

    Reassemble engine and reinstall in vehicle
    Reinstall cylinder heads with new gaskets, torquing head bolts in proper sequence from center outward in three stages (typically final torque 95-105 ft-lbs for AMC 390). Install pushrods in original positions, rocker arms, and adjust valves to specification. Install timing chain cover with new gasket, oil pan with new gasket, intake manifold with new gaskets, and all external components. Reinstall engine in vehicle reversing removal procedure. Connect all hoses, wiring, linkages, and fuel lines. Install new oil filter and fill with proper grade engine oil. Fill cooling system with proper coolant mixture.

Reassembly

1. Torque all cylinder head bolts following factory sequence pattern working from center outward
2. Adjust valve lash to AMC 390 specifications after initial assembly
3. Prime oil system by rotating oil pump with drill motor before starting engine
4. Double-check all electrical connections, vacuum lines, and fluid levels before starting
5. Verify all motor mount bolts are tightened to specification
6. Reinstall hood and align using original marked positions

Verification

• Start engine and immediately verify oil pressure registers on gauge
• Listen for unusual noises such as knocking, tapping, or excessive valve train noise
• Allow engine to reach operating temperature while monitoring for leaks (oil, coolant, fuel)
• Perform initial break-in period: avoid high RPM or heavy loads for first 500 miles, varying engine speed to allow rings to properly seat
• After 50-100 miles, retorque cylinder head bolts and readjust valves
• Change oil and filter after 500 miles of break-in operation
• Monitor oil consumption during first 1000 miles - consumption should decrease as rings seat properly
• Perform compression test after break-in period to verify all cylinders show even compression within 10% of each other

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