The overall straightness of the cylinder head and block face is held within very tight specification. Defects known as "waviness" or "depressions" cannot be surface machined out with ordinary equipment. Machining must meet manufacturer's specification on surface finish quality and be less than 0.001" inch (0.025 mm) level as measured under a known quality straightedge using a feeler gauge. If the engine has been overheated the cylinder head may have been damaged or warped. Re-surfacing will not correct this damage.
The head must not contain any impressions on its sealing surface deeper than 0.001" (0.025 mm). There must not be any scratches or gouges present, especially those which track to another sealing cavity or to the atmosphere.
Ensure that the mating cylinder block surface is completely free of solid contamination, corrosion, and fluids. Use Motorcraft Metal Surface Cleaner, F4AZ-19A536-RA or equivalent, to rid the surface of any material, which could later interfere with the gasket's sealing ability.
WARNING UNDER NO CIRCUMSTANCES ARE ANY ALUMINUM GASKET SURFACES TO BE CLEANED USING RAZOR BLADES, ROTARY ABRASIVE DEVICES INCLUDING ROLOC AND 3M BRANDED SCOTCHBRITE PRODUCTS, ROTARY WIRE BRUSHES, SINGLE HANDLED WIRE BRUSHES, HAND ABRASIVE SUCH AS SANDPAPER OR EMERY CLOTH, OR ANY CARBON STEEL BLADE. THESE TOOLS ARE PROVEN TO CUT AND DAMAGE ALUMINUM AND WILL DISRUPT THE POLISHED FINISH. ABRASIVE PARTICLES ARE ALSO SUSCEPTIBLE TO ENTERING THE ENGINE CAVITIES AND MAY CAUSE INTERNAL ENGINE DAMAGE. THE ONLY TOOLS ACCEPTABLE ARE PLASTIC AND WOOD SCRAPERS COMBINED WITH USE OF MOTORCRAFT METAL SURFACE CLEANER, F4AZ-19A536-RA, OR EQUIVALENT SOLVENT.
The original head bolts are to be discarded. Only new head bolts are acceptable for use in a head gasket repair. Use of old bolts can cause clamp load failure because they were stretched from the last torquing procedure either from the plant or a previous field repair. The new head bolt shanks and threads should be thoroughly cleaned, dried, and lightly lubricated. Oil the bolts and let oil drip for a minimum of 5 minutes. Use of too much oil may cause hydraulic lockup in the bolt hole.
The corresponding bolt holes in the cylinder block must be free of contamination consisting of dirt particles, coolant, and oil. Bolts can mechanically or hydraulically lock on top of these materials and cause for poor clamping of the cylinder head gasket. Use very lightly compressed air to blow out the bolt holes. Use care to prevent debris from scattering over the internal engine surfaces.
To clean the cylinder block gasket surface, a plastic or wood scraper in combination with Motorcraft Metal Surface Cleaner, F4AZ-19A536-RA, or equivalent solvent can be used with a portable shop vacuum. Move the scraper toward the vacuum nozzle to direct loosened material quickly away from the block surface.
It is not necessary to expect aluminum head surfaces to be shiny and bright after the vehicle has been in service. Sanding, scraping, or polishing will create surface depressions that cause leaks. The surface is expected to be flat within 0.001" (0.025 mm) and free of dirt, metal chips, and liquid contaminants. Any staining of the metal surface is considered normal.
Machining of aluminum heads and blocks is an unacceptable field practice for quality control purposes of flatness and surface finish standards. Removing material will also raise the risk of internal reciprocating components striking each other, as well as changing the emissions calibration of the engine. Machining practices of aluminum blocks and heads are not reimbursable. Ford Remanufacturers are authorized to perform this procedure and have the necessary equipment to put the specified surface finish on the head within original factory limits.