COSTS INVOLVED IN A REBUILD:
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Remove and Replace engine - $1500
Labour to strip down and rebuild motor - $1500-2000
Head service - $600
Miscellaneous gaskets, oils, etc etc - $500
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Forged pistons - $900 -> $3000
It should cost anywhere from about $4000 upwards to do a proper engine rebuild, not including any upgraded parts like forged pistons, rod bolts, etc etc... Add those to the rebuild cost.