Lately I noticed a taping noise coming out of my engine when it is cold. I have not isolated yet if it is related to valve train or piston slap. But it is very noticable. Goes away once the engine warms up.

Two things I did before I started hearing the noise.
1) I change my oil from regular to full synthetic. Could this cause the noise? My oil pressure runs about 50 - 60 always. Before going full synthetic, my presure will run about 50 when the rpms are high, but will drop down to about 20 - 30 when idling with the truck on drive. I can't remember what the oil pressure was when on park or neutral - best guess is about 40.
2) I never did liked the fast idle and so I backed out the fast idle screw where it won't fast idle at a higher rpm. After I started hearing the noise, I played around with it a little but there is no change. I did not think this will be a cause of engine noise, but decided to eliminate it as a cause anyways.

I am going to change my oil back to regular oil and see if the noise goes away. But I want to know your opinion if an oil change would do that.

Truck: 1979 F100. Engine: 302 with 600cfm edlebrock.

 

changing to synthetic could have caused this sure. also what brand oil filter you using?

 

Did you use the same weight synthetic as the mineral oil you were using? The synthetic oils are slicker, and have a lower viscosity so it may reveal some noises that are not present with regular oil. You could try a higher weight synthetic oil. FWIW I have had the same experience as you with synthetic oils and went back to mineral.

 

I use Micro gaurd oil filter. I have always used this filter and never had any problem until I change to synthetic. I never used Fram.
Also, some guy at the auto store said that once I use synthetic brand, I should not go back to regular. Is that true? Also, wondering why would synthetic oil do that? I always thought synthetic is better than regular oil.

 

Sorry Paul ! did not see your reply before hitting enter. You seem to have answered my questions !