I've been so preoccupied with rebuilding my Giulia Sprint GT Veloce and trying to get my 1900C SS project back on track that I've had no time to drive or participate in this corner of the forum...until now.
So last Spring I was driving our Giulietta (750F) when the water pump and fan blade failed. That led to rebuilding the pump and installing a later style fan blade, which led to us discovering that a couple of the valves were burned, which led to a rebuilt head with later cams (to improve drivability) which led to my current conundrum.
The builder of the head is not only a friend, but a trusted member of the North American Alfa Romeo community, and one who is very knowledgeable about 750/101/105/115 models. I don't believe the head is the cause for the symptom I'm about to describe.
If I didn't know any better I might think it was a rod knock, but I'm almost positive it's not a rod knock (I'll support this statement in a minute). There is a knocking noise coming from somewhere under the hood that occurs only between 3000 and 4000 RPM. I've drained the oil and there is no indication of any metal or shiny particulate in the oil which you'd expect if a conrod bearing had failed. The compression is healthy across all 4 cylinders so it's not a piston and valve kissing. I've removed the exhaust system so it's not a baffle. The engine is relatively low mileage (less than 20K miles) and was built by reputable people prior to my acquisition of the car. I cannot find anything attached to the engine that is loose which would cause this rattle, and it's not the timing chain or the tensioner. The carbs were gone through just recently and I don't hear any noise coming from the exhaust manifold. It does not have any cracks in it.
The only thing I haven't checked is the gearbox to see if something came loose inside the bell housing.
Who wants to weigh in on potential sources for the noise?
-tj in the Cruz Mtns
So last Spring I was driving our Giulietta (750F) when the water pump and fan blade failed. That led to rebuilding the pump and installing a later style fan blade, which led to us discovering that a couple of the valves were burned, which led to a rebuilt head with later cams (to improve drivability) which led to my current conundrum.
The builder of the head is not only a friend, but a trusted member of the North American Alfa Romeo community, and one who is very knowledgeable about 750/101/105/115 models. I don't believe the head is the cause for the symptom I'm about to describe.
If I didn't know any better I might think it was a rod knock, but I'm almost positive it's not a rod knock (I'll support this statement in a minute). There is a knocking noise coming from somewhere under the hood that occurs only between 3000 and 4000 RPM. I've drained the oil and there is no indication of any metal or shiny particulate in the oil which you'd expect if a conrod bearing had failed. The compression is healthy across all 4 cylinders so it's not a piston and valve kissing. I've removed the exhaust system so it's not a baffle. The engine is relatively low mileage (less than 20K miles) and was built by reputable people prior to my acquisition of the car. I cannot find anything attached to the engine that is loose which would cause this rattle, and it's not the timing chain or the tensioner. The carbs were gone through just recently and I don't hear any noise coming from the exhaust manifold. It does not have any cracks in it.
The only thing I haven't checked is the gearbox to see if something came loose inside the bell housing.
Who wants to weigh in on potential sources for the noise?
-tj in the Cruz Mtns