Intake Manifold Gasket

Replace the intake manifold gasket on a 1966 Chevrolet Corvette 327ci V8, including removal of carburetor, distributor, and ancillary components to access and reseal the manifold-to-block mating surface.

Warnings

Tools required

Parts

• Intake manifold gasket set (includes end seals) × 1 — Fel-Pro MS90026 or equivalent
• Intake manifold bolt set (if corroded) × 1 — Use OEM specification
• Carburetor base gasket × 1 — Use OEM specification
• Distributor base O-ring (if equipped) × 1 — Use OEM specification
• RTV silicone sealant (high-temp) × 1 — Permatex Ultra Black or equivalent
• Coolant (DEX-COOL) × 1 — Use OEM specification

Fluids

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

Preparation

1. Disconnect negative battery cable at battery.
2. Allow engine to cool completely (minimum 2 hours after last operation).
3. Remove air cleaner assembly and set aside in clean area.
4. Place drain pan under radiator petcock and drain coolant from radiator.
5. Locate and remove engine block drain plugs on both sides of block (1/4" NPT plugs typically located near freeze plugs) to drain coolant from block.
6. Tag and photograph all vacuum lines, ignition wires, and electrical connections for accurate reassembly.
7. Cover open ports and manifold runners with clean rags to prevent debris entry during disassembly.

Procedure

1. 1

   Disconnect fuel and throttle linkage
   Disconnect fuel line at carburetor inlet using two wrenches (one to hold hex on carburetor, one to loosen line nut) to prevent twisting the fitting. Cap or plug fuel line to prevent spillage. Disconnect throttle linkage at carburetor by removing cotter pin and clevis pin. Disconnect choke cable or choke hot air tube if equipped. Disconnect throttle return spring.
2. 2

   Remove carburetor assembly
   Label and disconnect all vacuum lines connected to carburetor (PCV, distributor advance, brake booster if present). Remove the 4 carburetor mounting nuts securing carburetor to intake manifold. Lift carburetor straight up to avoid damaging throttle shafts. Stuff clean rags into the intake manifold openings to prevent debris entry. Set carburetor aside on clean surface.
3. 3

   Mark and remove distributor
   Using masking tape on distributor body and intake manifold, mark the exact position of the distributor rotor orientation and the distributor body clocking position relative to the engine. This is CRITICAL for reinstallation. Disconnect distributor primary wire and vacuum advance line. Remove distributor hold-down clamp bolt using 1/2" wrench. Gently pull distributor straight up out of engine, noting if gear engages—shaft will rotate slightly as gear disengages. Do not crank engine with distributor removed.
4. 4

   Disconnect coolant hoses and accessories
   Disconnect upper radiator hose at intake manifold (use hose clamp pliers or screwdriver as appropriate). Disconnect heater hoses at intake manifold fittings—these may be 5/8" hose barbs on passenger side front of manifold. Disconnect coolant temperature sender wire. If equipped with automatic choke, disconnect choke coolant lines. Label any remaining vacuum lines connected to manifold and disconnect.
5. 5

   Remove valve covers (if necessary for access)
   On some 327 configurations, valve covers must be removed for access to intake manifold end bolts. Remove 6 valve cover bolts per side. Lift valve covers off—tap gently with rubber mallet if stuck. Set aside with gaskets. This provides access to end intake manifold bolts hidden under valve cover lip.
6. 6

   Remove intake manifold bolts
   Locate all 12 intake manifold mounting bolts: 8 bolts through the top of the manifold into valley, plus 4 end bolts (2 per end) at front and rear accessible from under valve cover area or externally depending on manifold design. Remove bolts in reverse order from center-out (start at ends, work toward center) to avoid warping manifold. Keep bolts organized for inspection.
7. 7

   Remove intake manifold
   With all fasteners removed, gently pry intake manifold loose from cylinder heads using plastic pry tool at casting ears—never pry between gasket surfaces. Lift manifold straight up and off engine. Manifold weighs approximately 35-40 lbs, use caution. Remove and discard all rags from ports. Immediately cover open cylinder head ports and lifter valley with clean shop towels to prevent debris entry.
8. 8

   Remove old gaskets and clean surfaces
   Carefully remove all old gasket material from intake manifold mating surfaces and cylinder head surfaces using plastic or brass gasket scraper—do not use steel scrapers that can gouge aluminum or cast iron. Remove front and rear intake manifold end seals from block. Clean all surfaces with solvent and shop rags until completely free of old gasket material, oil, and debris. Inspect manifold and head surfaces for warping or damage. Use straightedge to check for warping—maximum acceptable deviation is 0.010". Ensure bolt holes in heads are clean and free of coolant or oil.
9. 9

   Install new end seals
   Apply thin bead of RTV silicone sealant to the front and rear block-to-head joints (where timing cover meets heads and where block rear meets heads). Position new front and rear intake manifold end seals into place on block, pressing firmly into the valleys. The end seals should fit snugly into the recesses at engine front and rear. Apply small dab of RTV at the four corners where end seals meet head gasket surfaces to lock everything in position.
10. 10

    Install new intake manifold gaskets
    Position new intake manifold gaskets onto cylinder heads, aligning all port openings precisely. Most gaskets have alignment tabs or specific orientation—verify printing on gaskets indicates correct side up. Some installers use small dabs of grease to hold gaskets in position during manifold installation. Ensure gaskets overlap end seals properly at all four corners. Do not use additional sealant on gasket faces unless gasket manufacturer specifically requires it.
11. 11

    Install intake manifold
    Carefully lower intake manifold into position, aligning all ports with gaskets. Ensure manifold seats evenly on gaskets and end seals without shifting gaskets out of position. Verify distributor drive gear opening is clear. Start all 12 intake manifold bolts by hand, threading them in just enough to hold manifold in position but not compressed against gaskets. Verify no gasket edges are pinched or displaced.
    Torque spec

    Intake Manifold Bolts25 Nm (18 lb-ft)
12. 12

    Torque intake manifold bolts in sequence
    Torque intake manifold bolts in three stages, working from center bolts outward toward ends in a spiral pattern. First pass: torque all bolts to 10 lb-ft. Second pass: torque all bolts to 15 lb-ft in same sequence. Final pass: torque all bolts to 25 Nm (18 lb-ft) in same sequence. This progressive tightening ensures even gasket compression and prevents distortion. After final torque, wait 15 minutes and re-check torque on all bolts—some gasket compression may occur.
    Torque spec

    Intake Manifold Bolts25 Nm (18 lb-ft)
13. 13

    Reinstall distributor at marked position
    Rotate distributor shaft so rotor points to the mark made during removal. Insert distributor into engine, aligning distributor body with body position mark. As distributor gear engages with camshaft gear, shaft will rotate slightly—this is normal. When fully seated, rotor should align with original rotor position mark. If not aligned, remove distributor, rotate rotor slightly, and reinstall. Install distributor hold-down clamp and snug bolt finger-tight only—distributor will need slight adjustment during timing procedure. Reconnect distributor primary wire and vacuum advance line.
14. 14

    Reconnect coolant system
    Reinstall engine block drain plugs on both sides with thread sealant tape or pipe sealant. Reconnect upper radiator hose to intake manifold with hose clamp. Reconnect heater hoses to intake manifold fittings with clamps. Reconnect coolant temperature sender wire. If equipped with automatic choke coolant lines, reconnect those as well.
15. 15

    Reinstall carburetor and linkage
    Remove rags from intake manifold carburetor mounting surface. Install new carburetor base gasket. Set carburetor onto manifold, aligning mounting studs with holes. Install 4 carburetor mounting nuts and tighten in criss-cross pattern to snug—do not overtighten as carburetor body can crack (typical spec 12-15 lb-ft). Reconnect all vacuum lines per labels/photos. Reconnect fuel line to carburetor using two wrenches—tighten to snug plus 1/4 turn. Reconnect throttle linkage, choke cable, and throttle return spring. Verify throttle operates smoothly from idle to wide-open and returns freely.
16. 16

    Refill coolant system
    Fill radiator slowly with 10 quarts of DEX-COOL Extended Life coolant mixed per manufacturer instructions (typically 50/50 with distilled water). With radiator cap off, start engine and allow to warm to operating temperature while monitoring coolant level—add coolant as level drops due to air purging from system. Squeeze upper radiator hose to help purge air pockets. When engine reaches operating temperature and coolant level stabilizes, install radiator cap. Check for leaks at all hose connections and intake manifold gasket area.
17. 17

    Set ignition timing
    With engine at operating temperature, connect timing light to number 1 cylinder spark plug wire. Disconnect and plug vacuum advance line at distributor. Set engine idle to specification (typically 600-700 RPM in neutral). Aim timing light at timing marks on harmonic balancer—initial timing should be per underhood specification (typically 4-8 degrees BTDC for 1966 327). If adjustment needed, loosen distributor hold-down clamp and rotate distributor body slightly until timing is correct. Tighten distributor hold-down clamp securely. Reconnect vacuum advance line. Verify timing advances with throttle blip.

Reassembly

1. If valve covers were removed, reinstall with new gaskets torqued per specification (typically 4-5 lb-ft).
2. Reinstall air cleaner assembly with fresh filter if needed.
3. Reconnect negative battery cable.
4. Check and adjust carburetor idle mixture and speed as needed for smooth operation.
5. Double-check all vacuum line connections, fuel line security, and electrical connections.

Verification

• Start engine and verify smooth idle with no misfiring or rough running.
• Check for coolant leaks at all intake manifold gasket seams, especially at front and rear end seals.
• Check for vacuum leaks using carburetor cleaner spray around manifold perimeter—engine speed should not change if gaskets are sealing properly.
• Verify coolant temperature rises normally and heater produces hot air, confirming proper coolant circulation.
• After 15-minute test drive, recheck intake manifold bolt torque and coolant level when engine is cool.
• Monitor for oil consumption or coolant loss over next 100 miles—any issues indicate gasket leak requiring correction.

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