Exhaust Manifold

This procedure covers removal and replacement of one or both exhaust manifolds on the 1972 Ford F-100 with 302ci V8 engine, including disconnection of exhaust pipes and accessory components as needed.

Warnings

Tools required

Parts

• Exhaust manifold gasket set (both sides) × 1 — Fel-Pro MS 90018 or equivalent
• Exhaust manifold bolts (if corroded) × 16 — Use OEM specification
• Exhaust pipe flange gasket × 2 — Use OEM specification
• Exhaust pipe flange nuts × 4 — Use OEM specification

Preparation

1. Park vehicle on level ground and engage parking brake. Chock rear wheels.
2. Allow engine and exhaust system to cool completely (minimum 2 hours after last operation).
3. Apply penetrating oil to all exhaust manifold bolts, exhaust pipe flange nuts, and any heat shield hardware. Allow to soak overnight if possible.
4. Raise front of vehicle and support securely on jack stands at frame rails.
5. Disconnect negative battery cable.

Procedure

1. 1

   Disconnect exhaust pipes from manifolds
   Working from underneath the vehicle, locate the exhaust pipe flanges where they connect to each exhaust manifold. Remove the 2 nuts securing each exhaust pipe to its manifold flange. Separate the pipes from the manifolds and allow them to hang supported by their hangers. Discard old flange gaskets.
2. 2

   Remove spark plug wires and heat shields (if equipped)
   Remove spark plug wires from plugs on cylinders 1, 2, 3, 4 (passenger side) and 5, 6, 7, 8 (driver side) and secure out of work area. If heat shields are present on either manifold, remove the retaining hardware and set shields aside.
3. 3

   Remove passenger side manifold bolts
   Starting from the center and working outward, remove the 8 bolts securing the passenger side exhaust manifold to the cylinder head. Use a combination of extensions and universal joint as needed to access all fasteners. Note that some bolts may require access from above while others are easier from below. If any studs break off, mark their locations for extraction after manifold removal.
4. 4

   Remove passenger side exhaust manifold
   Carefully work the passenger side exhaust manifold free from the cylinder head studs. It may be necessary to rotate or angle the manifold to clear spark plugs and frame components. Once free, lower the manifold down and out through the engine compartment or from underneath, depending on clearance.
5. 5

   Disconnect dipstick tube (if necessary for driver side access)
   On the driver side, the dipstick tube may interfere with manifold removal. If needed, remove the dipstick and unbolt the dipstick tube bracket from the engine block. Carefully pull the tube from its mount to create clearance.
6. 6

   Remove driver side manifold bolts
   Remove the 8 bolts securing the driver side exhaust manifold to the cylinder head. Access is typically more restricted on this side due to steering components and frame clearance. Work from both above and below as necessary, using extensions and universal joints to reach all fasteners.
7. 7

   Remove driver side exhaust manifold
   Maneuver the driver side exhaust manifold free from the cylinder head. This side typically requires more manipulation due to steering linkage and frame rail proximity. Work the manifold forward and down, angling as needed to clear obstructions. Remove from underneath the vehicle.
8. 8

   Inspect and clean cylinder head mating surfaces
   With both manifolds removed, thoroughly inspect cylinder head exhaust ports for cracks or damage. Use a gasket scraper and wire brush to remove all old gasket material from the cylinder head mating surfaces. The surface must be completely clean and flat for proper sealing. Inspect all manifold studs/bolt holes and extract any broken studs using appropriate extraction tools.
9. 9

   Inspect exhaust manifolds
   Carefully inspect both exhaust manifolds for cracks, especially around the ports and at stress points. Check mating surfaces for warpage using a straightedge. Minor warpage (less than 0.010 inches) can be corrected by machining; severe warpage or cracks require manifold replacement. Clean manifold mating surfaces thoroughly with wire brush and gasket scraper.
10. 10

    Install driver side exhaust manifold
    Position a new exhaust manifold gasket on the driver side cylinder head, aligning all port openings. Carefully maneuver the driver side manifold into position, threading it onto the cylinder head studs/bolt holes. Start all 8 manifold bolts by hand, leaving them loose. Ensure gasket remains properly positioned.
11. 11

    Torque driver side manifold bolts
    Torque the driver side exhaust manifold bolts in a spiral pattern from center outward to proper specification. Tighten in three progressive steps: first to 15 ft-lbs, then to 25 ft-lbs, and finally to the final torque specification of 25-30 ft-lbs. Verify all fasteners are fully seated.
12. 12

    Install passenger side exhaust manifold
    Position a new exhaust manifold gasket on the passenger side cylinder head, aligning all port openings. Install the passenger side manifold onto the cylinder head, starting all 8 bolts by hand. Leave all fasteners loose and verify gasket alignment.
13. 13

    Torque passenger side manifold bolts
    Torque the passenger side exhaust manifold bolts using the same spiral pattern from center outward. Apply torque in three progressive steps: 15 ft-lbs, then 25 ft-lbs, and finally to 25-30 ft-lbs. Double-check that all fasteners are properly tightened.
14. 14

    Reconnect exhaust pipes to manifolds
    Install new exhaust pipe flange gaskets at each manifold connection point. Raise exhaust pipes into position and align flanges with manifold outlets. Install 2 new flange nuts at each connection and tighten securely (typically 25-35 ft-lbs). Ensure pipes are properly supported by hangers and not under stress.
15. 15

    Reinstall accessories and finalize
    If removed, reinstall the dipstick tube and bracket, securing to engine block. Reinstall any heat shields with their original hardware. Reconnect all spark plug wires to their proper cylinders in correct firing order. Reconnect negative battery cable. Lower vehicle from jack stands.

Reassembly

1. Always use new exhaust manifold gaskets; never reuse old gaskets even if they appear intact.
2. Replace any corroded or damaged manifold bolts to ensure proper clamping force.
3. Torque all exhaust manifold bolts in multiple progressive steps from center outward to prevent gasket distortion and warping.
4. Verify exhaust pipes are properly supported and not pulling or pushing on manifold flanges.

Verification

• Start engine and allow to reach operating temperature while monitoring for exhaust leaks at manifold-to-head joints and at exhaust pipe flanges.
• Listen for ticking or hissing sounds that indicate exhaust leaks. A stethoscope or piece of hose can help pinpoint leak locations.
• Check all manifold bolt torque after first heat cycle (after engine cools from initial warm-up).
• Visually inspect for any signs of exhaust gas leakage (black soot marks) around gasket surfaces.
• Verify no exhaust odor is present in cabin during operation, which would indicate a leak on the firewall side.

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