The engine has great pick up. runs good otherwise. trans seems to run strong and shifts good with no noise that i am aware of. may be starting to burn/pass oil in number 6 cyl. it has just had a water pump /head gasket change, but was making this noise before then. A/C works great and noise does not change when A/C is operated. all temps and pressures are good. removed belt and all pulleys seem tight with no wobble. hand pressure only, not engine running. if car sits for a while and started, there is no noise until engine gets up to operating temp, or at least that what it seems. once car has been run, noise will continue until shut off. again when engine is started and reached to 1500-1800 rpm, the noise goes away, but then returns later while driving. thanks for any help.