Resurfacing Heads & Blocks

To restore gasket sealing & flatness

• Surface damage from:Corrosion around water passagesCombustion gases Improper handlingEngine overheatingImproper torque sequence

Copyright 2003 Gary Lewis – Dave Capitolo

Resurfacing Heads & Blocks

Surfacing complications

• OHV in-line enginesValve clearance with non-adjustable rockersValve-to-piston clearance Possible detonation, higher compression ratios

Resurfacing Heads & Blocks

Surfacing complications

• OHC in-line enginesPossible detonation, higher compression ratiosRetarded valve timing – About 1° per .020”Piston-to-valve clearanceInstall timing cover before surfacing

Resurfacing Heads & Blocks

Surfacing complications

• OHV V-block enginesValve clearance with non-adjustable rockersValve-to-piston clearance Possible detonation, higher compression ratiosIntake manifold alignment

- Oil consumption- Vacuum leaks

Resurfacing Heads & Blocks

Compression ratio changes

• High vs. Low compression ratios

Octane requirements increase with compression Emissions & power increase with compressionDetonation chances increase with compression

Resurfacing Heads & Blocks

Surfacing machines

• SandingQuickLess preciseGood for quick clean-up of exhaust manifoldsDifficult to maintain precision

Resurfacing Heads & Blocks

Surfacing machines

• GrindingUses abrasive stonesCan cut through hard materialGood surface finish is possibleFinal passes are ‘sparked out’

Resurfacing Heads & Blocks

Surfacing machines

• Grinding (cont.)For Aluminum . . .

Take shallow cutsDress stone oftenUse soap on stone

Resurfacing Heads & Blocks

Surfacing machines

• MillingCarbide generally for AluminumCBN generally for IronWith good setup, heavy cuts are possibleHard spots dull cutters

Resurfacing Heads & Blocks

Surfacing machines

• MLS gasket preparationSurface finish – 20 AA micro-inchesLight cuts with slow feed ratesSharp cutters with lubricationDress stones often

Resurfacing Heads & Blocks

Stock removal

• Generally as little as possible (.020” total)• Specs may not be available• When available, specs = min thickness or max removal• Some composite gaskets compensate for .010”

• Stock removal may exceed measured warp

Resurfacing Heads & Blocks

OHC head surfacing

• Chain driven engines need timing cover installed• Top side can be surfaced for cam alignment• Use shims to restore cam height

Resurfacing Heads & Blocks

Diesel head surfacing

• Surface with pre-combustion chambers in place• Chambers may be difficult to machine• Measure valve recession on tear down• Restore valve recession by grinding seats

Resurfacing Heads & Blocks

Air cooled head surfacing

• Sealing surface is inside chamber• Seal surface is machined• Inside diameter of surface may be contoured• Surface deck to restore seal depth

Resurfacing Heads & Blocks

Resurfacing blocks

• To maintain parallelism to crankshaft• Provide a better seal• Match deck heights on V-blocks

Resurfacing Heads & Blocks

Manifold alignment on V-blocks

• Correction for port alignment• Correction for gasket crush

Resurfacing Heads & Blocks

Manifold alignment on V-blocks

• Distributors can be shimmed to prevent intermediate shaft binding

Resurfacing Heads & Blocks

Determining ratios

• Determine angle between cylinders• Determine angle of cylinder head

Resurfacing Heads & Blocks

Determining ratios

• For port alignment, surface . . . Intake side of head, or Intake side of manifold