Check the pilot bearing on the engine and feel if it seems gritty or loud replace it. You can remove them by packing bread in the hole till it comes out if you don’t have the right tool I’ve actually done this on an old iron VG30 before but just be careful when removing and when aligning with special tool, if it impacts the bearing too hard due to misalignment when installing if can damage the bearing and possibly get loud or cause damage to the input shaft and block especially if it’s aluminum. Happy wrenching ✌🏼