In other posts I have referred to a faint "knocking" that occurs in a limited rev range under load (around 2000-2500rpm when roilling and not at all when standing - hence the lack of a noise soundtrack) and the fact that this has come into being following a rebuild. Well, its still there (not surprising).
I eventually came across this great thread http://www.alfaowner.com/Forum/alfa-...500-rpm-5.html
that has been very interesting and helpful. As someone of limited virtue with a tool set and wary that a little knowledge is a dangerous thing this only helps me when talking to others (such as now).
So, for example, I have concluded that the noise COULD be caused by any one of the following:
Broken/damaged piston ring(s) - leading to piston slap
Worn valve guides
Worn hydraulic tappets
Worn cam lobes
Worn rear balance shaft bearings
Worn thrust bearing on gearbox end of crank
Worn inlet tappet guide holes/seats
Poor compression (from piston ring wear, burnt exhaust valve or…)
Poorly fitted balancer shaft belt
plus, possibly side effects from:
Variator continuity problem
Exhaust cam pulley (location peg)
Loose exhaust bracket
or a combination thereof.
I have left off big ends as I am sure these would have got rapidly worse and this hasn't happened in 4000 miles.
What I am hoping to establish is whether the rebuild in question would have included all these components and should have checked them all (other than the exhaust bracket) out prior to release back to me.
I guess I could just return it to the rebuilder unhappy as the noise has been evident since the rebuild but just maybe its coincidence.....
Your collected wisdom welcome...