I have done the head, rings,rod and main bearing all due to burning a hole in #2 piston in lean fuel condition,I dropt the front supsension to leave the engine in the car,looking back I should have take motor out,NOW I am thinking I should change the oil pump chain and at lessed the timing chain guides as they do have groves after 195000 km's,my question is what milage can I exspect out of timing parts-should I replace them,Kiwi