recently purchsed 87 GN has had tapping under valve covers on both sides goes away after about 2,000rpm's contacted the seller awesome guy and have no reason to think he was not telling me the truth about the engine, he told me it was rebuilt and only has 10,000 miles on it and the reason for the tapping is rhoades lifters, i beleive this but how loud should this tapping be from the lifters and valves, cause they dont seat until high idle.