Adjusting the hydraulic valve lifters on a 1966 Chevrolet Corvette 327ci V8 to ensure proper valve train operation and engine performance.

Warnings

Tools required

Parts

• Valve cover gaskets (pair) × 2 — Use OEM specification or Fel-Pro VS12812
• Valve cover grommets/seals × 8 — Use OEM specification
• Oil fill cap gasket × 1 — Use OEM specification

Preparation

1. Park vehicle on level surface and engage parking brake
2. Allow engine to cool completely (minimum 2 hours after running)
3. Disconnect negative battery cable
4. Remove air cleaner assembly and note carburetor linkage configuration
5. Disconnect spark plug wires and label for correct reinstallation
6. Remove any brackets or accessories that interfere with valve cover removal
7. Clean valve cover areas thoroughly to prevent debris from entering engine

Procedure

1. 1

   Remove valve covers
   Remove the bolts securing each valve cover using appropriate socket — verify exact bolt count and pattern against the specific cylinder head casting on this 1966 327 (typically 4 corner or staggered bolts per side). Carefully lift valve covers straight up to avoid damaging gasket mating surfaces. Inspect gasket surfaces on both covers and cylinder heads for damage or warping.
2. 2

   Clean gasket surfaces
   Use gasket scraper to remove all old gasket material from valve cover and cylinder head mating surfaces. Clean thoroughly with shop rags and ensure no debris falls into engine. Inspect valve train components for excessive wear or damage while covers are removed.
3. 3

   Position crankshaft for cylinder 1
   Rotate engine clockwise using breaker bar on crankshaft pulley bolt until the timing mark on harmonic balancer aligns with TDC (0 degrees) on timing tab. Verify that cylinder 1 is on compression stroke by confirming both intake and exhaust valves are closed (rocker arms loose). If either valve is open, rotate engine one complete additional revolution.
4. 4

   Adjust cylinder 1 valves
   With cylinder 1 at TDC compression stroke, loosen the rocker arm adjusting nut on both intake and exhaust valves. Tighten the adjusting nut slowly while spinning the pushrod with your fingers until you feel resistance (zero lash). Once zero lash is reached, tighten the adjusting nut an additional 1/2 to 3/4 turn to set proper hydraulic lifter preload. This provides approximately 0.020-0.060 inch lifter plunger travel.
5. 5

   Adjust remaining valves using firing order sequence
   Following the firing order 1-8-4-3-6-5-7-2, rotate the crankshaft to bring each successive cylinder to TDC on its compression stroke (both valves closed) before adjusting that cylinder's intake and exhaust valves. Confirm both rockers are loose at each position rather than relying on a fixed degree of rotation. Repeat the zero-lash plus one turn procedure for each cylinder's intake and exhaust valves.
6. 6

   Verify all adjustments
   After completing all 16 valves (8 cylinders, 2 valves each), systematically verify each rocker arm adjusting nut is tight and properly secured. Check that all pushrods move smoothly with spring pressure when pressing down on rocker arm. Rotate engine by hand two complete revolutions and listen for any unusual clicking or binding.
7. 7

   Install new valve cover gaskets
   Position new valve cover gaskets on cylinder heads, ensuring all bolt holes and grommets align properly. If the valve cover design uses bolt sealing grommets, replace them; note that 1966 327 perimeter/corner-bolt covers generally do not use bolt grommets. The gaskets should sit flat without adhesive on the 1966 application.
8. 8

   Reinstall valve covers
   Carefully position valve covers onto cylinder heads, aligning all bolt holes. Install the bolts per side finger-tight, then torque in a crossing pattern to approximately 7-12 ft-lbs (verify against factory spec for this application). Do not overtighten as this will distort stamped steel covers and cause leaks.

Reassembly

1. Reinstall any accessories or brackets removed for valve cover access
2. Reconnect spark plug wires according to labels and firing order
3. Install air cleaner assembly and reconnect all linkages
4. Reconnect negative battery cable
5. Check engine oil level and top off if necessary

Verification

• Start engine and listen for proper valve train operation with no excessive clicking or tapping
• Allow engine to reach operating temperature and verify no oil leaks from valve covers
• Engine should idle smoothly with no misfires or unusual noises
• Verify all rocker arms are receiving oil flow (visible through oil filler cap opening)
• Road test vehicle to ensure proper performance under load

More procedures for this vehicle