Engine noise

[sgaar]

Engine noise

I know that the title isn’t very telling so I’ll try to be more descriptive. At first I thought that this was valve noise but some further troubleshooting has led me to believe that it might be something else.

When I first start the engine everything is good and also as it gets warm idling. If I drive the car and the engine is under load that is when I start to hear the noise. As the RPM goes up so does the noise. This started after I took the car from a drive from NC to GA and it sounds metallic. As if the piston is hitting the valve but when I started on my trip to GA everything was fine which makes me doubt that it is that.

Since I initially through that it was the valves that needing adjustment I got a seeker blade and found a couple of valves where the thrust piece should be one size bigger. I got the thrust pieces today, got then swapped out but no change.

I should also say that the rocker arms, hydraulic compensating elements and the cam shaft has been replaced but everything was good before my drive to GA.

I have ordered the adjustment tool to see if the hydraulic compensating elements are good so here are my next steps:

- Check the compensating elements
- Make sure that the height of the elements are good and if not then the thrust pieces needs to be adjusted
- Try to move all of the rocker arms from one side to another and see if the problems moves (my thinking is that maybe not all of the aftermarket rocker arms are within spec)

There are no other problems with the car and apart from the noise and it pulls strong and there is no smoke from the exhaust.

Any suggestions would be great.

[angefurzen]

Just a wild guess -- if one of your CIS injectors has a bad spray pattern or has it's internal filter plugged, you could be running lean on one cylinder and pinging. Look at your spark plugs -- easiest way to check for detonation. Also, exhaust leaks close to the head often sound like a metallic tapping. This might not be noticable at idle, but will get much louder under load. You can use a mechanics stethoscope (or a tube) to listen for any possible leaks in the exhaust manifolds or manifold gaskets.

[sgaar]

Thanks. I should add that the injectors was replaced last year so I don't yjink that it is the spray pattern that is off. The manifold gasket might me it since it did start after a long trip.

I will pull the plugs tomorrow. When the engine is idleing there is a slight tapping (which is what led me to beleive that it was the valves) and it seems like it is around cyl. 4.

[sgaar]

OK, progress...! I went through the hydraulic compensating elements to see if possibly one of then had collapsed eventhough they are new. To my very big surprise I found that the thread surface on one of the rocker arms was worn completly down to the point where it was flat. This resulting in the valve not opening completely and closing too much.

This was not expected as the rocker arms were replace less than 1000 miles ago. The new cam shafts, rocker arms and hydraulic compensating elements were all purchased from ********AZ. This is not to ding them but rather the suppliers of parts to them as it looks as this subpar parts.

I'll try to contact them next week and see what they say but there is a groove on the thread plate about 1mm deep.