If the bolt tightens you do not need to re-tap the hole. The crank is not something you want to drill yourself because you would need to be dead on accurate. Was there a lock-washer with the bolt? An out of round pulley could cause a vibration but most that I see have a locking tooth that you need to line up. If that is bent or damaged that could be causing the problem. I would start by replacing the crank pulley and re-torqing the bolt. Blue Locktite is good but you must leave it cure before running the engine. If that doesn't hold I would see if maybe there is a problem with other pulley's etc. Very weird problem!!!
Answers & Comments
If the bolt tightens you do not need to re-tap the hole. The crank is not something you want to drill yourself because you would need to be dead on accurate. Was there a lock-washer with the bolt? An out of round pulley could cause a vibration but most that I see have a locking tooth that you need to line up. If that is bent or damaged that could be causing the problem. I would start by replacing the crank pulley and re-torqing the bolt. Blue Locktite is good but you must leave it cure before running the engine. If that doesn't hold I would see if maybe there is a problem with other pulley's etc. Very weird problem!!!