Engine noise at startup

[Pomorza]

Hey mates

So for the past couple of days when I start in the Z in the mornings - and in the afternoons after work - it makes a very quick knocking noise - lasts about three seconds maybe four. Once the noise goes away it doesn't come back. Engine doesn't seem to be low on power, isn't smoking and isn't consuming anymore oil then it already does (I have bad valve seals). I adjusted the valves about five months ago and other than the #6 exhaust valve they were fairly dead on before I did them. The only change in my maintenance has been to switch oils from Rotella T to Amsoil 10-40 (the one with high zinc - which actually makes the car run cooler and does - according to my arse dyno - give me more power).

Any thoughts? Suggestions? 

Cheers mates
Jan 

[Dave WM]

why not change the oil back and see if the knock goes away?

[Mark Maras]

 Could the problem be the oil filter?  I believe that the higher priced filters have a valve in them that prevents oil from draining out of it when the engine is off, which  theoretically allows the engine to build oil pressure a little sooner. Have you noticed any delay in the oil pressure gauge when starting the engine since the oil change?

[Patcon]

Too much clearance on the bearings. When the oil pressure comes up the knock goes away. Run a heavier weight oil, You're in Tucson you could easily run a 50W oil...It will help

[Zed Head]

I have that "problem".  A few dull thuds then smooth running.  Been doing it for ~20,000 miles at least with no change.  The filter should  speed up the pressurization process if the anti-drainback valve is working, but I think with thinner oil you'll always get a few knocks.  

I noticed when I ran Rotella that my oil pressure tended higher, despite the similar weight to other oils I had used.  Those viscosity numbers are from a lab, higher pressure readings in the engine indicate higher viscosity at running temperature.

[gundee]

Hydraulic lifter engine????

[Pomorza]

11 hours ago, Lumens said:

Hydraulic lifter engine????

Its an N47 head so I don't believe so. 

 

[Pomorza]

14 hours ago, Mark Maras said:

 Could the problem be the oil filter?  I believe that the higher priced filters have a valve in them that prevents oil from draining out of it when the engine is off, which  theoretically allows the engine to build oil pressure a little sooner. Have you noticed any delay in the oil pressure gauge when starting the engine since the oil change?

I run a wix filter, which I'm sure has an anti-drain back valve, but I'll give it a try. The pressure takes a few seconds to get up but no different then before. Its possible I have a faulty oil filter so I'll give it a shot on the next oil change, which is coming up soon 

Edited August 26, 2017 by Pomorza

[esmit208]

On Friday, August 25, 2017 at 8:33 PM, Pomorza said:

Hey mates

So for the past couple of days when I start in the Z in the mornings - and in the afternoons after work - it makes a very quick knocking noise - lasts about three seconds maybe four. Once the noise goes away it doesn't come back. Engine doesn't seem to be low on power, isn't smoking and isn't consuming anymore oil then it already does (I have bad valve seals). I adjusted the valves about five months ago and other than the #6 exhaust valve they were fairly dead on before I did them. The only change in my maintenance has been to switch oils from Rotella T to Amsoil 10-40 (the one with high zinc - which actually makes the car run cooler and does - according to my arse dyno - give me more power).

Any thoughts? Suggestions? 

Cheers mates
Jan 

Since you went inside the valve cover not long ago remove it again to inspect for something that may have come undone. If it wasn't doing it before chances are the torque on something may have backed off or something else may have worked it's way loose. Oil could be your issue but I would inspect under valve cover.