Engine Building? Huh Well Any Ways Yeah If You Have Just Some Tools And A Little Skill You Will Be Able To Pull Both Heads Off If You Have The Correct Tool To Compress The Valves Springs On A Bench And Replace The Valve Seals. Also Lapping The Valves At The Very Least Would Be Smart. A Really Skilled Shop Might Be Able To Replace The Valve Seals With The Heads On And The Correct Tools And Having The Clearance,, But Its Still A Pain And A Very Delicate Process, Drop A Retainer Or Anything Down In The Engine And Your Sol. Also You Don't Get To Lap The Valves This Way. Are You Going To Have To Set The Timing Oh Yeah.. Pop What Off? And Pop It Back On.. Or Just Keep It Im Not Sure What You Trying To Say... Anyways Good Luck