Replace the front main crankshaft seal on a 1966 Chevrolet Corvette 327ci V8 by removing the radiator, harmonic balancer, and timing cover to access the seal behind the crankshaft pulley.

Warnings

Tools required

Parts

• Front main crankshaft seal × 1 — Use OEM specification
• Timing cover gasket × 1 — Use OEM specification
• Oil pan gasket × 1 — Use OEM specification
• Gasket sealer (non-hardening) × 1 — Permatex Ultra Blue or equivalent

Fluids

• 5W-30 Conventional engine oil — 5 qt
• DEX-COOL Extended Life coolant — 10 qt

Preparation

1. Allow engine to cool completely for at least 2 hours
2. Disconnect negative battery cable
3. Raise and securely support vehicle on jack stands
4. Place drain pan under radiator and drain coolant completely
5. Place drain pan under engine and drain engine oil completely
6. Remove upper radiator hose and lower radiator hose
7. Remove fan shroud if equipped
8. Remove engine cooling fan (4 bolts attaching to water pump)

Procedure

1. 1

   Remove radiator assembly
   Remove the 2 bolts securing the radiator core support to the frame. Disconnect transmission cooler lines if equipped with automatic transmission. Carefully lift radiator straight up and out of engine compartment. Cap or plug transmission cooler lines to prevent fluid loss.
2. 2

   Remove drive belts and accessories
   Loosen and remove all engine drive belts (alternator, power steering, air conditioning if equipped). Remove the crankshaft pulley bolts (typically 4 bolts) securing the outer pulley to the harmonic balancer hub. Remove the outer crankshaft pulley.
3. 3

   Remove harmonic balancer
   Remove the single center bolt securing the harmonic balancer to the crankshaft. This bolt is torqued very tight and requires a breaker bar. Use a harmonic balancer puller tool threaded into the balancer hub. Tighten the puller center bolt gradually to press the balancer off the crankshaft snout. Do not strike or pry behind the balancer as this will damage it.
4. 4

   Remove timing cover fasteners
   Locate and remove all 10 bolts securing the timing cover to the engine block. These include bolts around the perimeter of the timing cover and typically 2 bolts attaching through the oil pan rail. Note the different bolt lengths for reinstallation.
5. 5

   Lower oil pan front section
   Remove the front 6 oil pan bolts to allow the front of the oil pan to drop slightly. You may need to raise the engine 1-2 inches using a floor jack under the oil pan with a block of wood for clearance. This provides access to separate the timing cover from the oil pan gasket junction.
6. 6

   Remove timing cover
   Carefully pry the timing cover away from the engine block using a pry bar at the designated pry points (usually cast bosses on the cover). Work around the perimeter gradually to break the gasket seal. Remove the timing cover, being careful not to damage the gasket mating surfaces on the block or oil pan.
7. 7

   Remove old front main seal
   The front main seal is pressed into the timing cover. Using a seal puller or pick tool, carefully pry the old seal out of the timing cover bore. Work around the seal circumference to avoid damaging the cover bore. Clean the seal bore thoroughly with a clean rag and inspect for any damage or scoring.
8. 8

   Clean all mating surfaces
   Thoroughly clean the timing cover gasket surface on the engine block using a scraper and wire brush. Remove all old gasket material without gouging the aluminum or cast iron surfaces. Clean the oil pan rail where it meets the timing cover. Clean the crankshaft seal surface (snout) with a clean rag, inspecting for any scoring or damage that could cause the new seal to leak.
9. 9

   Install new front main seal
   Lightly coat the outer diameter of the new seal with gasket sealer. Position the seal in the timing cover bore with the lip facing toward the engine (spring side toward the engine). Using a seal driver or appropriately sized socket that contacts only the outer edge of the seal, tap the seal squarely into the bore until it is fully seated and flush with the timing cover surface.
10. 10

    Install timing cover gasket and prepare surfaces
    Apply a thin bead of non-hardening gasket sealer to both sides of the new timing cover gasket. Position the gasket on the engine block, ensuring all bolt holes align. Apply gasket sealer at the junction points where the timing cover meets the oil pan rail (both corners). This is a critical leak point.
11. 11

    Install timing cover
    Lightly coat the crankshaft snout and seal lip with clean engine oil. Carefully position the timing cover onto the engine block, guiding the crankshaft through the new seal. Install all 10 timing cover bolts finger-tight, then torque in a crisscross pattern working from center outward. Without specific torque specs, tighten the small timing cover bolts gently (approximately 75-100 in-lbs / 6-8 ft-lbs) to avoid distorting the stamped-steel cover; verify against factory manual.
12. 12

    Reinstall oil pan front section
    Raise the front of the oil pan back into position against the timing cover and engine block. Apply fresh gasket sealer at the timing cover junction if needed. Install the front 6 oil pan bolts and torque evenly. If engine was raised, carefully lower it back to normal position.
13. 13

    Install harmonic balancer
    Ensure the crankshaft snout and harmonic balancer bore are clean and dry. Align the balancer keyway with the crankshaft key. Using a harmonic balancer installation tool (never strike with a hammer), press the balancer onto the crankshaft until it is fully seated. Install the center bolt and torque to specification (approximately 60 ft-lbs for the 327 small-block, but verify against factory manual).
14. 14

    Reinstall crankshaft pulley and accessories
    Position the outer crankshaft pulley onto the harmonic balancer hub. Install the 4 pulley bolts and torque securely. Reinstall all drive belts and adjust to proper tension (1/2 inch deflection at longest span). Reconnect alternator, power steering pump, and any other accessories removed.
15. 15

    Reinstall cooling system components
    Carefully lower the radiator back into position and secure with the 2 core support bolts. Reconnect transmission cooler lines if equipped. Install the engine cooling fan to the water pump (4 bolts). Reinstall fan shroud if equipped. Connect upper and lower radiator hoses and secure with clamps.

Reassembly

1. Refill cooling system with 10 quarts of DEX-COOL Extended Life coolant mixed 50/50 with distilled water
2. Refill engine with 5 quarts of 5W-30 conventional motor oil
3. Reconnect negative battery cable
4. Check all belt tensions and adjust as necessary

Verification

• Start engine and allow to idle while monitoring for any coolant or oil leaks around timing cover area
• Check for leaks at harmonic balancer seal surface after 5 minutes of running
• Allow engine to reach normal operating temperature and verify no leaks
• Shut off engine and recheck oil level after 10 minutes, top off as needed
• Inspect for coolant leaks around radiator connections
• Road test vehicle and recheck for any leaks from timing cover or front main seal area

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