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i am trying to figure out why certain years some engines are orange/red and others are blue


Why is the sky blue?
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ex 68/68 a-body engines can be either color


also 68/68 a-body engines can be either 225,273,318,340,383
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also, is it true that air conditionned HP cars had the engines painted blue while the non air versions were orange


NO - it isn't true, but in 1969 b-bodies - the 383HP automatic engines were "turquoise" with A/C & "orange" without.

The "WHY?"s the restoration crowd would like to have answered will probably never be understood or answered to everyone's satisfaction. Just the way manufacturing "consumables" is. Specific engines were painted specific colors during specific model years, few if any "bullet proof" documented exceptions exist.