Valve Job - Complete

Complete valve job including cylinder head removal, valve grinding, seat reconditioning, guide service, spring replacement, and reassembly for the 390ci V8 engine.

Warnings

Tools required

Parts

• Cylinder 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
• Valve stem seals × 1 — AMC 390 V8 valve seals, set of 16
• Valve springs (if worn) × 1 — AMC 390 V8 valve spring set
• Valve spring retainers × 1 — AMC 390 V8 retainer set
• Valve keepers × 1 — AMC 390 V8 keeper set
• Pushrod cover gaskets × 2 — AMC 390 V8 pushrod cover gaskets
• Valve cover gaskets × 2 — AMC 390 V8 valve cover gaskets
• Rocker arm shaft hardware × 1 — Use OEM specification
• Anti-seize compound × 1 — High temperature thread compound

Fluids

• Engine oil (refill after completion) — 5 qt
• Engine coolant — 4 qt

Preparation

1. Disconnect negative battery cable
2. Drain engine coolant completely from radiator and block drain plugs
3. Drain engine oil and remove oil filter
4. Remove air cleaner assembly and carburetor
5. Remove alternator, power steering pump, and air conditioning compressor (if equipped) without disconnecting hoses
6. Disconnect all vacuum lines, fuel lines, and electrical connections from cylinder heads, labeling each for reinstallation
7. Remove distributor and mark position relative to engine block
8. Remove intake manifold completely
9. Remove both exhaust manifolds
10. Remove valve covers and pushrod covers
11. Support engine from below with jack stands under oil pan using wood blocks for protection
12. Label or photograph rocker arm assembly orientation before removal

Procedure

1. 1

   Remove rocker arm assemblies and pushrods
   Remove rocker arm shaft retaining bolts in reverse order from tightening sequence (from ends toward center). Lift off rocker arm shaft assemblies as complete units. Remove all 16 pushrods, keeping them in order by cylinder number and intake/exhaust position. Store pushrods upright in a numbered holder or cardboard template to maintain original positions.
2. 2

   Remove cylinder heads
   Remove cylinder head bolts in reverse order from tightening pattern (work from outer bolts toward center). Use breaker bar if necessary. Carefully break head seal by tapping gently with rubber mallet if stuck. Lift heads straight up using engine hoist or with assistance. Place heads on padded surface or head stand. Remove and discard old head gaskets. Clean all gasket material from engine block deck surface using gasket scraper, being careful not to gouge aluminum or cast iron surfaces.
3. 3

   Disassemble valve train components
   Mount cylinder head securely on head stand or workbench. Using valve spring compressor, compress each valve spring and remove valve keepers using magnetic tool. Slowly release spring tension and remove retainer, springs, and valve stem seals. Remove each valve from combustion chamber side, keeping all components organized by cylinder and valve position. Store valves in numbered rack maintaining intake/exhaust identification for each cylinder.
4. 4

   Clean and inspect cylinder heads
   Thoroughly clean cylinder heads in solvent tank, removing all carbon deposits from combustion chambers and valve seats. Clean valve guide bores and oil return passages with rifle brush. Dry completely with compressed air. Inspect heads for cracks using dye penetrant or magnaflux, paying special attention to valve seat areas and between valve seats. Check cylinder head deck surface for warpage using straightedge and feeler gauge across length, width, and diagonally. Maximum allowable warpage is 0.007 inches. If warped beyond specification, heads must be milled flat.
5. 5

   Measure and service valve guides
   Using telescoping gauge and micrometer, measure inside diameter of each valve guide. Measure valve stem diameter with micrometer. Calculate valve-to-guide clearance. Standard intake clearance is 0.001-0.003 inches, exhaust is 0.002-0.004 inches. If clearance exceeds 0.005 inches intake or 0.006 inches exhaust, guides must be knurled, reamed oversize for oversize stem valves, or replaced with guide liners. This typically requires machine shop services.
6. 6

   Inspect and reface valves
   Clean all carbon from valve faces and stems using wire wheel. Inspect each valve for burning, pitting, warping, or cracking. Measure valve stem wear using micrometer at multiple points. Check valve face runout by rotating valve in V-block with dial indicator on face. Maximum runout is 0.002 inches. Reface valves on valve grinding machine to 45-degree angle for both intake and exhaust. Remove only enough material to clean up pits and restore smooth surface. Ensure valve margin remains at least 1/32 inch thick after grinding.
7. 7

   Recondition valve seats
   Using valve seat cutting tools or grinding stones, cut intake seats to 45 degrees and exhaust seats to 45 degrees (AMC 390 uses 45-degree seats for both). Cut or grind seats to achieve proper seat width of 0.060-0.080 inches for intake and 0.070-0.090 inches for exhaust. Use 30-degree top cut and 60-degree throat cut to narrow and position seat contact area. Seat should contact valve face at center or slightly toward valve tulip. Apply Prussian blue to valve face, insert valve with light spring pressure, rotate valve, and check contact pattern. Adjust seat cuts until achieving continuous contact band at proper width and position.
8. 8

   Lap valves to seats
   Apply thin layer of fine valve lapping compound to valve face. Insert valve into guide and attach lapping tool to valve head. Rotate valve back and forth while applying light downward pressure, lifting valve occasionally to redistribute compound. Continue until achieving continuous matte grey contact pattern around entire valve face and seat. Clean all lapping compound thoroughly from valves and seats using solvent and compressed air. Test seal by pouring solvent into intake and exhaust ports from combustion chamber side; valve should hold liquid without leakage.
9. 9

   Measure and test valve springs
   Measure free height of each valve spring using vernier caliper. Standard free height is approximately 2.0 inches (verify against AMC specification manual). Measure installed height requirement. Test spring pressure using spring tester at specified compressed height. Replace springs that are more than 1/16 inch shorter than specification or show more than 10% pressure loss. Check springs for squareness by standing on flat surface and measuring with square; replace if out of square exceeds 5/64 inch. Replace all springs as set if more than 25% are out of specification.
10. 10

    Reassemble valves into cylinder heads
    Lubricate valve stems with assembly lube or engine oil. Install new valve stem seals on guides using appropriate driver or socket to avoid damaging seal lips. Insert each valve into its original guide position (or follow new valve positioning if valves were replaced). Install valve springs with closely wound coils toward cylinder head. Install spring retainers. Compress springs with valve spring compressor and install keepers in valve stem grooves, ensuring keepers are fully seated in grooves. Slowly release compressor and verify keepers are locked in place. Tap valve stem tip lightly with plastic hammer to confirm keeper engagement. Repeat for all 16 valves.
11. 11

    Prepare engine block deck surface
    Clean engine block deck surfaces thoroughly, removing all old gasket material without gouging surface. Clean oil and coolant passages in block deck. Use compressed air to blow out head bolt holes; any liquid in bolt holes will cause hydraulic lock and prevent proper torque. Chase head bolt threads in block using appropriate tap to ensure clean threads. Install new head bolts if old bolts show thread damage or stretching. Verify block deck surface is clean, dry, and free of debris.
12. 12

    Install cylinder heads
    Position new head gaskets on block deck, ensuring correct orientation with all coolant and oil passage holes aligned. Gaskets typically have front orientation markings and specific top side. Do not use sealant on head gaskets unless specifically required by gasket manufacturer. Carefully lower cylinder heads onto block, aligning with dowel pins if equipped. Install all head bolts finger-tight. Following AMC 390 tightening sequence (consult service manual for specific pattern, typically starting at center and working outward in spiral pattern), torque head bolts in three stages: first to 40 ft-lbs, second to 65 ft-lbs, and final to manufacturer specification (typically 95-100 ft-lbs for AMC 390). Allow engine to sit for 30 minutes, then re-torque all bolts to final specification in sequence.
13. 13

    Install pushrods and adjust valves
    Lubricate pushrod ends and rocker arm contact points with engine assembly lube. Install each pushrod in its original position, ensuring lower end properly seats in lifter cup. Position rocker arm shaft assemblies on cylinder heads, aligning oil supply holes. Install rocker shaft retaining bolts and tighten gradually from center outward to prevent binding. Torque rocker shaft bolts to specification (typically 19-25 ft-lbs for AMC 390). Rotate engine by hand using socket on crankshaft bolt. Adjust valve lash according to AMC specification: typical specification is zero lash (tighten rocker adjustment until zero clearance, then tighten additional 1/2 turn). Adjust intake and exhaust valves for each cylinder with that cylinder at TDC compression stroke.
14. 14

    Complete reassembly
    Install valve covers with new gaskets, tightening bolts evenly to prevent gasket distortion. Install pushrod covers with new gaskets. Install intake manifold with new gaskets, torquing bolts in proper sequence from center outward. Install exhaust manifolds with new gaskets. Reinstall distributor in original position. Reconnect all vacuum lines, fuel lines, and electrical connections according to labels. Reinstall alternator, power steering pump, and air conditioning compressor. Install carburetor with new gaskets and reconnect linkage and fuel line. Install air cleaner assembly.
15. 15

    Fill fluids and initial startup
    Install new oil filter and fill engine with recommended quantity and grade of engine oil. Fill cooling system with proper coolant mixture. Reconnect battery. Prime oil system by cranking engine with ignition disabled until oil pressure registers on gauge. Enable ignition and start engine. Check immediately for oil leaks, coolant leaks, and unusual noises. Allow engine to reach operating temperature while monitoring for leaks. Check and adjust idle speed and timing to specification. After initial 20-minute run period, recheck all head bolts and retorque if necessary when engine is cold. Recheck valve adjustment after 500 miles of operation.

Reassembly

1. Double-check all head bolt torque values after engine cools following first startup
2. Verify valve cover and intake manifold bolts are properly torqued to prevent oil and vacuum leaks
3. Ensure all electrical connections and vacuum lines are reconnected according to original positions
4. Recheck valve adjustment after initial break-in period of 500 miles

Verification

• Engine should start readily and idle smoothly without unusual valve train noise or ticking
• Confirm oil pressure reaches normal specification within seconds of startup
• Verify no oil leaks from valve covers, pushrod covers, or cylinder head gasket areas
• Check for no coolant leaks from head gasket areas after reaching operating temperature
• Perform cylinder compression test showing even compression across all cylinders (typically 140-160 psi for AMC 390)
• Verify no excessive blowby from crankcase breather indicating valve sealing issues
• Monitor engine temperature to confirm proper coolant circulation through cylinder heads
• Road test vehicle and confirm normal power delivery and no misfires under load

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