Complete removal and replacement of both cylinder head gaskets on a 1966 Corvette 327ci V8, including disassembly of intake/exhaust manifolds, valve train components, and cylinder heads.

Warnings

Tools required

Parts

• Cylinder head gasket (left) × 1 — Fel-Pro 1003 or equivalent
• Cylinder head gasket (right) × 1 — Fel-Pro 1003 or equivalent
• Intake manifold gasket set × 1 — Fel-Pro MS90042 or equivalent
• Exhaust manifold gaskets × 2 — Fel-Pro 1404 or equivalent
• Valve cover gaskets × 2 — Cork or rubber composite OEM-style
• Cylinder head bolt set (if reusing, inspect for stretch) × 1 — Use OEM specification
• Intake manifold bolt kit × 1 — Use OEM specification
• Exhaust manifold stud/bolt kit × 1 — Use OEM specification
• Valve cover bolt grommets × 1 — Use OEM specification
• Thermostat housing gasket × 1 — Use OEM specification
• Water pump gasket (if disturbed) × 1 — Use OEM specification
• Carburetor base gasket × 1 — Use OEM specification
• Pushrods (if worn or bent) × 16 — Use OEM specification
• Rocker arm studs (if damaged) × 16 — Use OEM specification
• RTV silicone sealant (high-temp) × 1 — Permatex Ultra Black or equivalent

Fluids

• 5W-30 Conventional Engine Oil — 5 qt
• DEX-COOL Extended Life Coolant (Orange) — 10 qt

Preparation

1. Park vehicle on level surface and allow engine to cool completely (minimum 4 hours).
2. Disconnect battery negative terminal and secure cable away from post.
3. Drain engine coolant completely into appropriate container by opening radiator petcock and removing radiator cap.
4. Drain engine oil and remove oil filter.
5. Remove air cleaner assembly and label all vacuum lines before disconnecting.
6. Label and photograph all electrical connections, fuel lines, and linkages for reference during reassembly.
7. Prepare clean workspace for storing removed components in order.
8. Have fire extinguisher readily available when working around fuel system.

Procedure

1. 1

   Remove upper engine accessories and components
   Remove distributor cap and mark distributor rotor position relative to housing with paint pen, then mark housing position relative to block. Remove distributor hold-down clamp and lift distributor out carefully. Remove spark plug wires from plugs and label each wire's cylinder number. Remove all 8 spark plugs. Disconnect throttle linkage, choke cable, and fuel line from carburetor (use two wrenches to prevent twisting fuel line). Remove PCV valve and breather from valve covers. Disconnect temperature sender wire and upper radiator hose from thermostat housing.
2. 2

   Remove valve covers
   Remove the 4 valve cover bolts from each valve cover (8 total). Gently tap valve covers with rubber mallet if stuck, then lift off. Remove and discard old gaskets. Inspect pushrod guide plates and rocker arm assembly for obvious damage.
3. 3

   Remove rocker arm assemblies and pushrods
   Loosen each rocker arm stud nut evenly while noting valve adjustment positions if adjustable rockers are present. Remove the rocker arm studs and rocker arms, placing them in marked containers by cylinder number and position (intake/exhaust). Remove all 16 pushrods and store vertically in labeled holder or cardboard template maintaining exact original position - pushrods MUST return to original locations. Inspect pushrod ends for wear or damage and measure for straightness by rolling on flat surface.
4. 4

   Remove intake manifold
   Remove the 12 intake manifold bolts working from outside to inside in reverse of tightening sequence. Carefully lift intake manifold straight up - it may require gentle prying at designated pry points (not between sealing surfaces). Remove and inspect intake manifold gaskets and end seals. Stuff clean shop rags into intake ports on cylinder heads to prevent debris from entering engine.
5. 5

   Remove exhaust manifolds
   Working from underneath vehicle if necessary, disconnect exhaust pipes from exhaust manifolds at flange connections. Remove the 5 exhaust manifold bolts from each manifold (10 total). Note that corner bolts may be studs with nuts. Remove both exhaust manifolds and set aside. Inspect manifolds for cracks, particularly around ports.
6. 6

   Remove cylinder head bolts and heads
   Remove all 17 cylinder head bolts from each cylinder head (34 total) working from outside to inside pattern. Some bolts may be different lengths - note their positions. Carefully break cylinder heads loose from block using appropriate pry points (never pry between sealing surfaces). Lift each cylinder head straight up and off dowel pins. Place heads on clean padded surface, combustion chamber side up.
7. 7

   Inspect cylinder heads and block surfaces
   Remove and discard old head gaskets. Thoroughly clean all gasket material from cylinder head and block deck surfaces using plastic scraper - NEVER use metal scrapers that could gouge surfaces. Clean with solvent and compressed air. Place precision straight edge across deck surfaces in multiple directions and check for warpage using feeler gauge. Maximum allowable warpage is 0.003 inch in any 6-inch span, 0.006 inch overall. If beyond specification, heads must be professionally resurfaced. Inspect head bolt holes in block for thread damage and chase with thread chaser if needed. Blow out all bolt holes with compressed air to remove oil/coolant.
8. 8

   Inspect and prepare cylinder bores
   With heads removed, inspect cylinder bores for scoring, excessive ridge at top, or glazing. Measure bore for out-of-round if wear is suspected. Clean top of pistons carefully with solvent-soaked rag (rotate crankshaft to access each piston at top of stroke). Verify all pistons move freely and none show damage. Stuff clean rags around exposed cylinders to prevent debris entry during head installation preparation.
9. 9

   Install new head gaskets and position cylinder heads
   Verify block deck and head surfaces are completely clean and dry. Position new head gaskets over block dowel pins with 'TOP' or 'FRONT' markings facing up and toward front of engine. Do NOT use sealant on head gaskets unless specifically called for by gasket manufacturer. Carefully lower each cylinder head onto dowel pins, aligning with gasket. Ensure heads are fully seated before installing bolts.
10. 10

    Install and torque cylinder head bolts
    Lightly oil cylinder head bolt threads and underside of bolt heads with engine oil. Install all head bolts finger-tight, ensuring correct bolt lengths in proper positions. Torque cylinder head bolts in three steps following proper sequence (center bolts first, then working outward in spiral pattern): First pass to 25 ft-lbs, second pass to 50 ft-lbs, final pass to 65 ft-lbs. Allow 30 minutes for gaskets to compress, then perform final re-torque to 65 ft-lbs in same sequence.
11. 11

    Install pushrods and rocker arm assemblies
    Apply engine assembly lube or heavy engine oil to both ends of each pushrod. Install all 16 pushrods into their ORIGINAL locations, ensuring each seats fully in lifter cup (rotate pushrod while pushing down to verify seating). Install rocker arms onto studs in original positions. Thread rocker arm nuts down until they just contact rocker arms - do NOT tighten yet.
12. 12

    Adjust valves to initial setting
    Rotate crankshaft until #1 piston is at top dead center (TDC) on compression stroke (both valves closed, timing mark aligned). Adjust rocker arm nuts on #1 cylinder to zero lash (point where pushrod just stops spinning freely), then tighten 1 additional turn. Following firing order (1-8-4-3-6-5-7-2), rotate engine 90 degrees at a time and adjust each cylinder's valves when that cylinder reaches TDC compression. This provides initial adjustment; final adjustment after warm-up is recommended.
13. 13

    Install exhaust manifolds
    Position new exhaust gaskets on cylinder heads. Install exhaust manifolds and start all bolts/studs finger-tight. Torque exhaust manifold fasteners to 25 ft-lbs working from center outward. Reconnect exhaust pipes to manifold flanges with new gaskets, torquing flange nuts to 35 ft-lbs.
14. 14

    Install intake manifold
    Remove shop rags from intake ports. Apply thin bead of RTV silicone to front and rear block valley corners where end seals meet side gaskets. Position intake manifold end seals, then position intake gaskets on heads (ensure port alignment is correct). Apply small dab of RTV at four corners where gaskets meet end seals. Carefully lower intake manifold into position, ensuring all gaskets stay in place. Install all 12 intake manifold bolts finger-tight. Torque intake manifold bolts in sequence from center outward: first pass 15 ft-lbs, second pass 25 ft-lbs, final pass 30 ft-lbs. Allow 20 minutes for RTV to set before adding coolant.
15. 15

    Install valve covers and accessories
    Position new valve cover gaskets on heads (use small dabs of RTV to hold in place if needed). Install valve covers and torque bolts to 5 ft-lbs with new grommets. Reconnect thermostat housing and upper radiator hose. Install all 8 spark plugs and torque to 25 ft-lbs. Reconnect spark plug wires to correct cylinders. Install distributor with rotor aligned to original marked position and housing aligned to block marks, then install hold-down clamp finger-tight. Reconnect all vacuum lines, fuel line, throttle linkage, choke cable, temperature sender, PCV valve, and breather per original photos/labels.
16. 16

    Refill fluids and prepare for startup
    Install new oil filter and refill engine with 5 quarts of 5W-30 conventional oil. Close radiator petcock and refill cooling system with 10 quarts of DEX-COOL coolant mixed 50/50 with distilled water. Reconnect battery negative terminal. Reinstall carburetor air cleaner assembly. Double-check all connections, bolts, and hoses are properly secured.

Reassembly

1. Verify all fasteners are torqued to specification and no tools or rags remain in engine bay.
2. Confirm all electrical connections, vacuum lines, and fuel lines are reconnected per original configuration.
3. Check that valve covers, intake manifold, and exhaust manifolds show no signs of fluid leakage before starting.
4. Ensure coolant level is correct and cooling system is properly bled of air.

Verification

• Prime oil system by cranking engine for 10-15 seconds with distributor disabled (disconnect coil wire) until oil pressure gauge shows pressure.
• Start engine and immediately verify oil pressure registers. If no pressure within 10 seconds, shut down immediately.
• Check for coolant, oil, or exhaust leaks while engine warms to operating temperature. Address any leaks immediately.
• Verify engine reaches normal operating temperature (160-180°F) and thermostat opens properly.
• After engine reaches full temperature, shut down and allow to cool for 30 minutes, then re-torque cylinder head bolts to 65 ft-lbs following same sequence.
• Perform hot valve lash adjustment after engine is fully warmed: with engine running, adjust each rocker to zero lash plus 1/2 turn (traditional method for hydraulic lifters).
• Test drive vehicle and monitor for overheating, unusual noises, oil pressure, and performance issues.
• After 500 miles, check valve cover and intake manifold for any signs of seepage and re-torque if needed.
• Change oil and filter after initial 500-mile break-in period to remove any assembly residue.

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