I have a 2003 chevy impala 3.4 L , 50K MILES . When I start the car in the morning there is valve clatter, it is NOT a knock AND it only sounds like it is the front bank of cylinders. It will go away in 3-7 seconds. I use 5-30w oil, changed 3-6k miles, the recommended anti-drainback filter is used. Checked the oil pressure at the sending unit, 43-45 lbs with a guage. I noticed that the bottom of the AC compressor is a damp with oil and road dirt and where the crankshaft pulley is , the engine has very slight oil seepage. There is not any oil on the ground and I do not have to top off the oil level.
so what do you think ?