If you look on the old site at this thread:
http://www.alfagtv6.com/discus/messages ... 20000117pm
(or just search for "push rod" (in quotes)) you find a discussion that the noise may be from the valve train and not the bottom end.
A quote from that thread from someone named Tim:
"This is a very interesting thread regarding the mysterious warm engine knock that seems to be common for the Alfa V-6.
I don't believe this knock is always lower-end related as some suggest. The lower end of the Alfa V-6 is built especially rock solid as independent test have proven; for example as the Callaway turbo dyno bench test showed.
Wrist pin knock typically will occur when an engine is cold and then it will decrease with the rise to operating temp. My BMW 2002 has this type of knock.
I believe this myterious V-6 knock is coming from the upper end, perhaps worn cam bearings, push rods, rockers or something up there? Obviously temp related.
BTW: A decent test for worn main bearings is to run the engine to full temp and put the gas on hard, if the oil pressure drops while doing this then more than likely the main bearings are badly worn. For accuracy sake it is probably a good idea hook up diagnostic digital oil pressure meter while doing this type of test.
A good test for rod bearings is to run the engine to full temp and then increase the gas, then let off the gas suddenly. During this transition, when letting off the gas, worn rod bearnings will knock slightly. Also at cold start the rods will knock until oil pressure comes up, sure fire sign that the rod bearings are worn."