carl wrote:
> Hi,
>
> Can I bring another question to this forum ? I looked at the archives, but
> found nothing similar for this noise pattern or situation. And I wonder what
> a mechanic would say, given lash values are correct for most of the dealers.
>
> My car has had valves tightened a bit too much, now they're at correct valve
> lash. For a while, I hear too much noise coming from the cover. Valve lash
> increases with temperature ( is it always so ? ) and seems lower in
> frequency and much less noticeable when warm
>
> It is loudest on a cold engine, and in the afternoon, with engine still
> warm, is never that loud again. It also becomes very high in frequency when
> cold when the throttle is released, after driving in low gear and low load,
> the clatter increases just after release in volume and frequency, and
> diminishes after about a second ...
>
> Does the noise pattern, like after throttle release, point to something
> worse ( low- high end or main bearing ) ? I thought they would make heavier
> noise. There could have been oil issues in the past. Also, timing could have
> been too early 4 degrees for a long time, or late 4 degrees for 1000 miles
> now, giving more than normal bearing load ?
>
> Now this valve train has a OHC, two rocker shafts and 12 valve rockers with
> 4 exhaust ones. The rockers are cast aluminium, with iron or steel adjuster
> screws. I imagine it is not such a big deal to install new rockers and
> shafts, and even a camshaft, and adjust valve lash again. But from where can
> this noise come when valve lash is correct ? The car has 35 k miles and oil
> was changed just at 33k5 miles. Is there something with aluminium rockers
> and steel adjustment screws, which should not be overtightened ( they
> tighten even further when hot ) ? They could have been.
>
> Looking forward to any advice,
>
> MTIA,
>
> Carl

A rapping noise on overrun as you describe sounds like rod bearings to
me, GF had the same noise on her Corrado and new rod bearing shells
made it go away

nate