I have just got a 1985 manual accord, it has an 1800 motor & goes well but over about 2000RPM the engine is very noisey, like a thumping low pitch rumble, I would guess big end bearings but it is really quiet & normal up to 2000RPM even under load. It uses no oil & has done 280,000KM. Any ideas? And also I thought I would check the ignition timing but I can't find the timing marks, are they on the top of the crank pulley wheel or somewhere else?