Resurfacing Heads & Blocks
To restore gasket sealing & flatness
• Surface damage from:
Corrosion around water passages
Combustion gases
Improper handling
Engine overheating
Improper torque sequence
Copyright 2003 Gary Lewis – Dave Capitolo
Resurfacing Heads & Blocks
Surfacing complications
• OHV in-line engines
Valve clearance with non-adjustable rockers
Valve-to-piston clearance
Possible detonation, higher compression ratios
Resurfacing Heads & Blocks
Surfacing complications
• OHC in-line engines
Possible detonation, higher compression ratios
Retarded valve timing – About 1° per .020”
Piston-to-valve clearance
Install timing cover before surfacing
Resurfacing Heads & Blocks
Surfacing complications
• OHV V-block engines
Valve clearance with non-adjustable rockers
Valve-to-piston clearance
Possible detonation, higher compression ratios
Intake 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 compression
Detonation chances increase with compression
Resurfacing Heads & Blocks
Surfacing machines
• Sanding
Quick
Less precise
Good for quick clean-up of exhaust manifolds
Difficult to maintain precision
Resurfacing Heads & Blocks
Surfacing machines
• Grinding
Uses abrasive stones
Can cut through hard material
Good surface finish is possible
Final passes are ‘sparked out’
Resurfacing Heads & Blocks
Surfacing machines
• Grinding (cont.)
For Aluminum . . .
Take shallow cuts
Dress stone often
Use soap on stone
Resurfacing Heads & Blocks
Surfacing machines
• Milling
Carbide generally for Aluminum
CBN generally for Iron
With good setup, heavy cuts are possible
Hard spots dull cutters
Resurfacing Heads & Blocks
Surfacing machines
• MLS gasket preparation
Surface finish – 20 AA micro-inches
Light cuts with slow feed rates
Sharp cutters with lubrication
Dress stones often
Resurfacing Heads & Blocks
Stock removal
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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
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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
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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