i have a 91 prelude with the b21a1 motor bored 40 over and a 84mm copper head gasket i had a bad idling problem and would surge up to 2500 rpm and i found out that i was losing compression into my coolant system but the head that was on the car was shaved 3 times so i pulled the head and no crack in block or gasket and am putting a stock head onto it now but pretty sure it will still have the idling problem when i get done havent been able to get it to run right and idle right since ive had ive rebuilt the motor if you have any advice let me know please.