Alfa Romeo Repair: Medium grumble, disc clutch, jumper wire

Question
Hi Dave-

Thanks a lot for all the previous help you`ve given me. The news is that I have my 1982 Alfa Spider Veloce all put together and is running very well. I had to physically ground the injection computer with a jumper wire though in order to get all four injectors to operate!

My problem is this: After starting the engine on this car, I can hear a fairly loud but dull grumble coming from the rear of the engine, or front of the transmission, most audible from the right side of the car. To me, it sounds like a bearing is worn, or running dry. The engine is completely rebuilt to include new main bearings, rod bearings, thrust bearings, pistons (10:1 ratio), sleeves, .010 under crank on all journals, machined flywheel (flywheel screws torqued to the proper torque, and sealed with Locktite Red) with a new throwout bearing, disc, clutch cover, and pilot bushing for the trans input shaft. Oil pressure on the factory gauge reads normal. The car was started initially with Exxon Superflow 5W30 and a Fram oil filter.

With a long screwdriver as a stethoscope, the noise seems to be coming from the bellhousing area. With the clutch disengaged (clutch pedal held down to the floor) the noise does not change at all in pitch or volume. A few times at idle, the noise dissappeared temporarily, and I noticed that when it began again, it caused a slight load on the engine, along with a light squeak upon takeup of the load.

The only other information I can give you is that the replacement trans is used and never rebuilt to my knowledge. It is from a 1974 GTV, and I received it without it`s original bellhousing, and drained of oil. It has been filled with Redline 75W90. Also, the car is still off the ground pending repair on a broken rear spring, and has not yet been driven.

Any assistance would be greatly appreciated!

Joe

Answer
Hi Joe,

Boy... this is a toughy without being there.  Maybe you can clarify something for me... From your question:

>"With a long screwdriver as a stethoscope, the noise seems >to be coming from the bellhousing area. With the clutch >disengaged (clutch pedal held down to the floor) the noise >does not change at all in pitch or volume. A few times at >idle, the noise dissappeared temporarily, and I noticed >that when it began again, it caused a slight load on the >engine, along with a light squeak upon takeup of the load."

Are you saying that when you depress the clutch, the noise doesn't vary or it only makes the noise with the clutch disengaged?  

Obviously, if you depress the clutch and the sound doesn't change, then it's unlikely the transmission is involved. It's also unlikely that clutch or release bearing is involved.   That leaves the flywheel or something in the engine itself.  I should tell you that sound can travel in the engine.  I had a squeal once and it seemed louder near the bellhousing.  At least louder than from the front of the block.  I took off the fan belt and started the engine and it went away.  It was a water pump.  Don't ask me how come it was louder in the rear than at the front, but I'd never actually put the probe on the pump itself.  When I did after replacing the belt, it nearly deafened me.  Not to say you have a bad water pump, but this does sound like a bearing.
Tell me about having the crank turned?  Those cranks are Nitrided and really not supposed to be turned and Alfa does not offer undersized bearings.  Of course, Mains and rods from a 1750 or early 2 liter will work and they ARE available.  Were the clearances checked, or did you just trust the machinist.  I bought a .010 under crank set once for a Chev V8, and put it together without doing my usual plastigage check.  One bearing was so tight the engine would barely turn.
You could also have an oil passage closed or partially closed.  Sometimes it doesn't affect the oil pressure enough to show on all but the most sensitive gauge.

Try the fan belt thing first.  Once you do that, I would wait and listen to it for a short while.  If it gets louder then you are going to take the engine back apart. If it gets quieter or goes away, then I would drive it until something quits.  Run it long enough either way that when you find it, it will be obvious.  

This could be nothing to worry about or it could be very serious.  Without looking at it myself, I can't help you much beyond this.  If you have any other indication or symptoms you'd like to pass along, please do.  

dave