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Engine knocking occurring at high rev.

Posted: Mon Dec 12, 2005 12:41 pm
by gtv6milano
Situation:
-Cruising 4th gear at 4000rpm, and If I do full throttle(from 4000rpm), engine start making slight knocking.
-If I accelerate slowly, it is OK. Also, when I using 1st or 2nd or 3rd gear, it seems fine.

Engine:
3.0L Milano, New spark plugs & wires, new Distributor cap & roter, new coil(not bosch)
new dist vacuum advance.

I have checked ignition timing as STATIC: F mark. But, at 3000rpm, the timing is much more
than M mark. So, looks like ignition timing is too advanced at high rev.

I also tried changing ignition timing as 0.5 degree? BTDC *my timing light is cheap one, can't read
exact degree, the timing is, like 1mm from P (TDC) mark. It's work, much better than before, doesn't
make knocking mostly. Is it caused by Ignition advance ECU ? I am not sure which crank pulley
installed my engine (Milano or GTV6) but both F mark is 2 degree I think.

Posted: Tue Dec 13, 2005 12:31 pm
by gtv6milano
I might have some wrong information regarding the static ignition timing.

GTV6(2.5) ..... 2 deg BTDC
Milano(3.0)......7 deg BTDC

If so, my crack pulley could be Milano's. ......??

Crank pulley on my car
http://www015.upp.so-net.ne.jp/alfaromeo/5974.JPG

It looks like 7 or 8 degree from TDC(P)

Please let me know if it was Milano's? or any comment will help me.
Thanks in advance

Posted: Tue Dec 13, 2005 2:40 pm
by Murray
Going from memory (My car is in storage) I would say that you have a Milano pulley.The distance between TDC "P" and static setting "F" is greater than on my GTV6.

Posted: Tue Dec 13, 2005 3:43 pm
by gtv6milano
Thanks for the info.Murray, and sorry to bothering all. It was my big mistake.

measured the crank diameter today, and calculated as follow.

The diametr of this crank pulley is 144 mm, the circumference of this pulley should be 358.14mm
2 degree = 1.98mm,
7 degree = 6.96mm

So, 2 degree on this pully is just about 2 mm from TDC(P) line...... :shock:

I didn't doubt the pulley or static timing was different.