IF YOU WISH TO KEEP YOUR CORE OR KNOW THAT YOUR CORE IS NO GOOD, YOU MAY ADD THIS CORE CHARGE TO YOUR ENGINE ORDER AND NOT BE REQUIRED TO RETURN ONE. HOWEVER IF YOU CHOOSE TO RETURN A CORE WITHIN 30 DAYS YOU MAY RECEIVE A FULL REFUND ON YOUR CORE . UPON INSPECTION OF YOUR RETURNED CORE WE WILL ISSUE YOU A REFUND . CORE MUST BE THE SAME AS THE PURCHASED ENGINE.