Complete removal and replacement of the intake manifold on a 1966 Chevrolet Corvette 327ci V8, including carburetor removal, accessory disconnection, and gasket replacement.

Warnings

Tools required

Parts

• Intake manifold gasket set × 1 — Use OEM specification or Fel-Pro MS 90026
• Intake manifold end seals (front and rear) × 1 — Use OEM specification
• RTV silicone sealant (high-temp) × 1 — Permatex Ultra Grey or equivalent
• Carburetor base gasket × 1 — Use OEM specification for installed carburetor
• Thermostat housing gasket × 1 — Use OEM specification

Fluids

• DEX-COOL Extended Life Coolant (Orange) — 10 qt

Preparation

1. Ensure engine is completely cold to the touch
2. Disconnect negative battery cable and secure away from battery terminal
3. Place drain pan under radiator and drain cooling system via radiator petcock or lower radiator hose
4. Remove air cleaner assembly and set aside in clean area
5. Label all vacuum lines with masking tape and marker before disconnection
6. Take photographs of carburetor linkage setup and vacuum line routing for reference

Procedure

1. 1

   Disconnect fuel and vacuum lines
   Disconnect the fuel line at the carburetor inlet using two wrenches (one to hold the fitting, one to loosen the line). Plug the fuel line with a rubber cap or bolt to prevent fuel spillage. Disconnect all vacuum lines from the carburetor and intake manifold, referring to your labels and photographs. On the 327, this typically includes distributor advance line, brake booster line (if equipped), crankcase ventilation/PCV line (if equipped), and transmission vacuum modulator line if equipped with automatic transmission.
2. 2

   Remove carburetor and linkage
   Disconnect the throttle linkage rod at the carburetor ball stud. If equipped with automatic transmission, disconnect the kickdown linkage. Disconnect the choke cable or choke heat tube. Remove the 4 carburetor mounting nuts and carefully lift the carburetor straight up off the studs. Place carburetor in a clean area with shop rags covering the openings to prevent debris entry.
3. 3

   Disconnect ignition and electrical components
   Disconnect the distributor primary wire (small wire from coil to distributor). Disconnect any temperature sender wires mounted in the intake manifold or cylinder heads. If equipped, disconnect the alternator brackets that may interfere with manifold removal.
4. 4

   Remove upper radiator hose and heater hoses
   Loosen the hose clamps and remove the upper radiator hose from the thermostat housing on the front of the intake manifold. Remove both heater hoses from the intake manifold (typically one at the front and one at the rear on the passenger side). Expect residual coolant to drain from these connections.
5. 5

   Remove distributor
   Mark the position of the distributor rotor relative to the distributor body with a marker or scribe. Mark the position of the distributor body relative to the intake manifold. Remove the distributor hold-down clamp bolt and clamp. Carefully pull the distributor straight up out of the manifold, noting the rotor will rotate slightly as the drive gear disengages. This ensures correct reinstallation timing.
6. 6

   Disconnect accessory brackets and remaining components
   Remove any remaining brackets attached to the intake manifold including power steering pump brackets, air conditioning compressor brackets, alternator brackets, or ignition coil mounting brackets. On 1966 models, the coil is often mounted to a bracket bolted to the intake. Remove these brackets but do not disconnect hydraulic or refrigerant lines unless necessary; instead, support components with wire or rope.
7. 7

   Remove intake manifold bolts
   Remove all 12 intake manifold mounting bolts in reverse order of tightening sequence (work from the ends toward the center, alternating sides). The small-block Chevy intake uses bolts that pass through the manifold into the cylinder heads at an angle. Keep bolts organized by location as some may be different lengths. Note that some intake bolts may be different lengths than others; keep them organized by location for correct reinstallation.
8. 8

   Remove intake manifold
   Gently pry the intake manifold loose from the cylinder heads using a pry bar placed against a reinforced area of the manifold (never pry against sealing surfaces). The manifold may be stuck due to old gasket material and RTV. Once loose, lift the manifold straight up, tilting the rear upward first to clear the distributor opening. Watch for any remaining connected components. Place the manifold on a clean work surface with the gasket surface facing up. Verified detail (A cast-iron small-block Chevy intake manifold (standard on a 1966 327) typically weighs closer to 40-45 pounds; only aluminum performance intakes are in the 25-30 lb range. The 1966 327 base intake was cast iron.): The cast-iron intake manifold weighs approximately 40-45 pounds (aluminum manifolds are lighter).
9. 9

   Inspect and clean lifter valley
   With the manifold removed, inspect the lifter valley for debris, sludge, or coolant contamination (which would indicate a previously leaking gasket). Use a shop vacuum to remove any loose debris. Stuff clean shop rags into the lifter valley to prevent any debris from falling into the crankcase during gasket removal. Do not allow anything to fall past the lifters into the oil pan.
10. 10

    Remove old gaskets and clean sealing surfaces
    Carefully remove all old gasket material from the cylinder head sealing surfaces using a gasket scraper or razor blade held at a shallow angle. Work carefully to avoid gouging the aluminum or cast iron surfaces. Remove the old front and rear intake manifold end seals from the engine block. Clean all sealing surfaces thoroughly with brake cleaner or carburetor cleaner and a wire brush. Remove the shop rags from the lifter valley and vacuum out any remaining debris. All surfaces must be completely clean, dry, and free of oil or coolant for proper gasket sealing.
11. 11

    Install new end seals and gaskets
    Apply a thin bead (approximately 1/8 inch) of RTV silicone sealant to the front and rear edges of the engine block where the timing cover and rear block meet the cylinder heads. Press the new rubber intake manifold end seals into position at the front and rear of the block, ensuring they fit into their locating grooves. Apply a small dab of RTV at the corners where the end seals meet the cylinder heads (these four corners are common leak points). Position the new intake manifold gaskets on the cylinder heads, aligning the gasket ports with the head ports. The gaskets have alignment tabs that fit into notches on the heads. Some installers use a small amount of RTV or gasket adhesive to hold gaskets in position, but this is not required if working carefully.
12. 12

    Install intake manifold
    Carefully lower the intake manifold into position, tilting the rear upward to clear the distributor opening, then settling it straight down onto the gaskets. Ensure the manifold seats fully against all gaskets and end seals without shifting them out of position. Visually verify that all ports align correctly and no gasket edges are protruding into the ports or overhanging the sealing surfaces.
13. 13

    Install and torque intake manifold bolts
    Install all 12 intake manifold bolts finger-tight, ensuring they thread in smoothly without cross-threading. Following a proper tightening sequence (start at the center bolts and work outward in a spiral pattern, alternating sides), torque the bolts in three stages: first to 15 ft-lbs, then to 25 ft-lbs, and finally to the specification of 30 ft-lbs (verify against GM service manual for 1966 327). This gradual tightening prevents gasket distortion and ensures even clamping pressure across all sealing surfaces.
14. 14

    Reinstall distributor
    Rotate the distributor shaft until the rotor points to the mark you made during removal. Insert the distributor into the intake manifold opening, aligning the distributor body with your reference mark. As the distributor gear engages with the camshaft gear, the rotor will rotate slightly; this is normal. The distributor should drop fully into place with the rotor aligned to the original position and the body aligned to the body reference mark. Install the hold-down clamp and bolt, tightening just enough to hold position but still allow minor rotation for timing adjustment.
15. 15

    Reconnect coolant hoses and lines
    Install new hose clamps if originals are damaged. Reconnect the upper radiator hose to the thermostat housing with a hose clamp. Reconnect both heater hoses to the intake manifold fittings with hose clamps. Ensure all clamps are positioned properly on the beaded portion of the fittings and tightened securely.
16. 16

    Reinstall accessory brackets and components
    Reinstall all accessory brackets in reverse order of removal, including alternator brackets, power steering brackets, air conditioning brackets, and ignition coil bracket. Torque bracket bolts to appropriate specifications for their size. Reconnect the distributor primary wire to the coil and distributor. Reconnect all temperature sender wires and other electrical connections to the intake manifold area.
17. 17

    Install carburetor
    Place a new carburetor base gasket on the intake manifold with the gasket holes aligned with the mounting studs. Carefully lower the carburetor onto the studs, ensuring the gasket remains in position. Install the 4 carburetor mounting nuts and tighten in a criss-cross pattern to approximately 8-12 ft-lbs (verify against carburetor manufacturer spec) to ensure even seating without warping the carburetor base.
18. 18

    Reconnect linkage, fuel, and vacuum lines
    Reconnect the throttle linkage rod to the carburetor ball stud. If equipped with automatic transmission, reconnect and adjust the kickdown linkage. Reconnect the choke cable or choke heat tube. Reconnect the fuel line to the carburetor inlet fitting using two wrenches, tightening securely but not over-tightening the brass fitting. Reconnect all vacuum lines according to your labels and photographs: distributor advance, PCV, brake booster, transmission modulator, and any other vacuum-operated accessories.
19. 19

    Refill cooling system and check for leaks
    Close the radiator petcock or reconnect the lower radiator hose if it was removed. Fill the cooling system with conventional ethylene glycol (green) antifreeze mixed 50/50 with water (total capacity approximately 10 quarts). Fill the radiator completely and also fill the engine block through the upper radiator hose opening if possible to reduce air pockets. Install the radiator cap. Reconnect the negative battery cable.
20. 20

    Initial startup and leak check
    Start the engine and allow it to idle. Immediately check for fuel leaks at the carburetor inlet connection. Check for coolant leaks around the intake manifold gaskets, end seals, hose connections, and thermostat housing. Check for vacuum leaks (rough idle or hissing sounds). The engine may run rough initially due to air in the cooling system; this is normal. Allow the engine to reach operating temperature with the heater on full hot to help purge air from the system. As the thermostat opens and coolant circulates, the level in the radiator will drop; add coolant as necessary until the level stabilizes.

Reassembly

1. Torque all fasteners to specifications in proper sequence
2. Use new gaskets for all sealing surfaces; do not reuse old intake gaskets or end seals
3. Apply RTV silicone at the four corners where end seals meet cylinder heads to prevent leaks
4. Verify distributor timing marks align correctly before final tightening to prevent ignition timing issues
5. Bleed cooling system completely to prevent overheating and ensure proper heater operation

Verification

• Start engine and verify smooth idle with no rough running or vacuum leaks
• Check all gasket surfaces for coolant or oil leaks with engine at operating temperature
• Verify no fuel leaks at carburetor or fuel line connections
• Confirm proper engine operating temperature (thermostat opening, heater producing hot air)
• Check coolant level after engine has cooled; top off as necessary
• Test drive vehicle and verify proper throttle response and engine performance
• Re-check intake manifold bolt torque after first heat cycle (engine has reached operating temperature and cooled completely)
• Set ignition timing to specification using timing light (typically 4-8 degrees BTDC for 1966 327)

More procedures for this vehicle