Alfa 156 2.5V6 flywheel balance(inbalance)

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FERRARIST
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Alfa 156 2.5V6 flywheel balance(inbalance)

Post by FERRARIST » Sat Dec 01, 2012 1:01 pm

While upgrading my gearbox with Quaife, 6 paddle clutch on my RWD mid-endine 156 2.5V6, i really want to remove some weight from my flywheel.
Problem is that there is different opinions about how Alfa 156 V6 is balanced. Some said that only crankshaft pulley have inbalance on it, another that they must be balanced all together - crankshaft with pulley and flywheel.
There is not many places here in BG that can do balancing of all 3 parts, that's why i want to remove from the flywheel, and balanced it alone.
I can't see under the small rpm reading plate attached to the flywheel if there is any counter weight as with the pulley, and my guess is that there will be no problem.
Any opinions?
Thanks

Guy Croft
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Re: Alfa 156 2.5V6 flywheel balance(inbalance)

Post by Guy Croft » Sat Dec 01, 2012 3:57 pm

Don't mess with it.

Just leave it alone.


GC
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corriedw
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Re: Alfa 156 2.5V6 flywheel balance(inbalance)

Post by corriedw » Wed May 01, 2013 11:49 am

The Alfa v6 is balanced without the flywheel. The flywheel is in balance on its own and can be swopped without harm. I have done it on my GTV and at least a half a dozen guys in my club did it as well. The std dual mass flywheel is a lot heavier and they don't last. So it is common to go to the 2.5 flywheel and the GTA clutch with the engine in the car. (But if you change to different/upgraded pistons and rods on the v6, you have to rebalance or the main bearing will turn oval)

Guy Croft
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Re: Alfa 156 2.5V6 flywheel balance(inbalance)

Post by Guy Croft » Wed May 01, 2013 12:13 pm

Good - This indicates that this V6 crank is internally balanced (though not all are, eg: Fiat 130 V6). Assuming you are correct, I would not know, never done one.

However, just bolting a FW on a pre-balanced crank by no means assures the pair will be in balance as an assembly. That is merely an assumption and a dangerous one.

Irrespective of type the crank-FW must be considered as a mating pair and the balance (as an assembly) checked and corrected accordingly. Sorry to be brutal but the fact that folk have gotten away with it is frankly neither here nor there.

GC
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corriedw
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Re: Alfa 156 2.5V6 flywheel balance(inbalance)

Post by corriedw » Wed May 01, 2013 2:20 pm

Point taken, I can merely state that I haven't had trouble in 4 years/50000 km including a few trackdays

FERRARIST
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Re: Alfa 156 2.5V6 flywheel balance(inbalance)

Post by FERRARIST » Wed May 01, 2013 2:38 pm

My experience - had perfectly balanced my old 2.5V6 FW to zero vibration.....
1 - engine run without crank pulley and with FW - huge vibration....
2 - with pulley and same balanced FW - less vibration, but still present.....
Bought another 2.5V6 FW from another 156's - and immediately tried it after "2" - engine runs as it should......
Because my mid-engine, RWD conversion seems to work as i expected, i bought 3.0V6 from Alfa 166, and my plan is to use my 156's pulley with my 2.5V6 disbalanced OE FW......have 166's pulley, but dont have it's duall mass FW, and even if i had it - it's too heavy for a trackday car.......however if there is vibration with 156's pulley i can use 166's one.....

Guy Croft
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Re: Alfa 156 2.5V6 flywheel balance(inbalance)

Post by Guy Croft » Wed May 01, 2013 3:18 pm

Good balance practice, my code:

Experience quite simply does not prove the rule!

GC
Guy Croft, owner

FERRARIST
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Re: Alfa 156 2.5V6 flywheel balance(inbalance)

Post by FERRARIST » Wed May 01, 2013 3:39 pm

Yes, i agree.....but here in BG we simply don't have any other options than experimenting such a things and that's because we don't have some proper tools to balance entire assembly - pulley-crankshaft-FW together as whole. Or at least machines that can do that is about 40-50 years old.....and i don't mean my city or nearby.....i mean entire country.....

Guy Croft
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Re: Alfa 156 2.5V6 flywheel balance(inbalance)

Post by Guy Croft » Wed May 01, 2013 4:44 pm

Understood completely and thank you for telling me, I write these things for the guidance of all readers, you understand!

As I said, understood,thanks,

G
Guy Croft, owner

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