oil pressure and valve train noise after warm up

well the F head is running strong, this might be nit picky, but i would like to keep her running. Somthing I noticed, when the engine is cold, the oil pressure at idel is great - 30 - 40 lbs. it drops as the engine warms up to operating temp. when warm, if the idel is down, the oil presure drops below 20lbs - close to 10.

the valve train noise follows the oil pressure drop, I just rechecked teh clearances, (18 intake, 16 exhaust) they are dead on, but as the engine warms up, tap, tap, tap, tap, tap. plenty of oil in there, they are getting oil, so why the noise?

currently have 10/30 in the motor adn I really do not want this to be an oil debate thread.

Metal expands as it heats up, so why tapping? - wouldn't the clearances being smaller /coser together - less room to tap?

sorry for two questions in the same thread - dropping oil pressure, louder valve train noise, but I notice they are both related to the engine warming up

 

I think if you go to a 10/40 oil that your tapping will go away. Also are you driving this rig long enough to evap the fuel (dilution of oil) out of engine to maintain good viscosity?

 

Faint valve train noise at idle is normal for engines that use splash lubrication with solid lifters and flat tappets, it will get more pronounced when the engine is warm and the oil gets hot. So long as you have sufficient oil pressure and valves maintain their adjustment between scheduled check there should not be anything to worry about.

If you have 10psi+ at idle with a hot engine and 35psi+ at and above 2000 rpm you should be in good shape.

 

There are plenty of previous threads about flat tappet engines, ZDDP and oil recommendations. A conventional 10W30 oil is likely not appropriate for a flat tappet engine - up to you, but I'd encourage you to read the previous threads.

What Brian P wrote is right - the oil gets thinner as the engine heats up, and oil pressure will drop. A good rule of thumb is a minimum of 10 psi for each 1000 rpm.

Mechanical lifters clatter. Hydraulics were adopted both because of the reduced maintenance and because the zero-lash design is quieter.