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Could someone explain why exactly the flywheel is supposed to be balanced with the crankshaft? Given that you reinstall it in the same orientation as when you took it off, if the crankshaft is balanced with the flywheel and you lighten and re balance the flywheel then shouldnt it all be in the same balance it had from the factory? Is there something I am missing?!
By the by: anyone see my cry for 164 24v flyhwheel help, in the parts classifieds?
Vittorio

Vittorio: Are you aware there is a guy who makes lightweight Aluminum flywheels for these engines and sells them on Evil Bay? It might be best to ask him about them.

The V6 flywheels are not zero balanced, maybe you were not aware of that?

OK, the standard flywheel is not zero balanced.


I never visited a factory, but difficould to believe that on assembling-line in Milano they had hundrets of containers with premounted crankshafts/flywheels.
The whole lot of space and transportation, I imagine in wood-boxes.

Isnt it possible, that the flywheels came in different containers, pre-balanced to a special weight, what performes +/- with crankshafts ?
Then, mounted together as they came in.

Could it be possible to balance a flywheel to the same condition,
the factory flywheel has?

Any suggestion..

Werner

A v6 engine has moments that cannot be balanced internally and require external balancing (unlike a straight 6 which requires no balancing at all). The flywheel mounts to the engine only 1 way, so I don't see a problem with having thousands of flywheels that have an offset balance mounted at the factory (which is exactly what happens).
Once you lighten the flywheel you remove materail evenly from all sides (kinda) but the balancing factor (think of it as counterweight) of the flywheel changes. After you do that on a v6 engine you need everything rebalanced - flywheel, crankshaft with rods and pistons on and front crank pulley all together. Not difficult to do at all, but requires that you take engine apart. Another possible way (although not the best option) will be to take the stock flywheel to a balance shop. Have them "zero" the flywheel with a counterweight and then attach the same counterweight in the same position to the lightened flywheel and balance it like that. Remember that the flywheel goes on the engine only one way.

I am currently looking at having my stock flywheel machined. I am planning to have the bottom end balanced as a unit. Has anyone in the US done this recently? I am wondering how much it generally costs.

Some of you might have seen this already as I posted it on the other forum. This is a jig my dad made to re-balance the flywheel on my 75 after lightening and without engine balancing. The original flywheel was mounted and the jig balanced to the flywheel. Then the flywheel was lightened, and bolted back on the jig and balanced to 0 balance factor, which returns the flywheel back to original balance.

Great !
Nice idea, the jig... can it used with a mount for balancing
motorcycle wheels "at home", or only for sending to a balancing-shop?

Very interesting if it could be a "homebalancing" method...

yes, the ideal is getting out the complete crank.
But who likes to do this if its not necessary for a engine rework.



thanks
Werner

It's not just the flywheels that were engine-specific - it's the crank-pulleys as well!

In another post somewhere I laid out 4 pulleys, took pictures and posted - there were two 3.0 Verde/Americano 3.0 units, one GTV6 2.5 and one Milano/75 2.5 pulley each - THEY WERE ALL DIFFERENT - on the rears and on the leading-edges. So, I still don't see how the fleeBay aluminium flywheel guy can be selling these as a "bolt-on" replacement, or how we get away/have managed to get away with swapping flywheels and pulleys between motors all of this time...

I mean, guys putting 2.5 Milano/75 units on 3.0 12 valve 164 S/QV engines and into TA cars, 3.0 12 valve flywheels on 24 valve 3.0 motors and in to TA cars etc etc! Perhaps the differences from motor to motor is minimal enough to where the average arse-dyno doesn't notice it?

Looking at the flywheels for each of those 4 motors they were ALL different in terms of the balancing as well! I too was a non-believer that Alfa would have taken the time to individually balance the motors - even externally - until that moment!

The only consistencies were that the counter-weights on the two 2.5s were the same and the counter-weights on the two 3.0s were the same... Other than this the balancing drill-holes were all SIGNIFICANTLY different on EACH of the 4 pulleys.

JJ,

having worked in pattern shops (part of a foundry) i know that depending on the casting method, the make up of the material, the day, and which side of the bed the foundryman got up on that day, one pattern will make castings that weigh differently. also the gates and risers get changed sometimes and that will have an effect also.

when i worked for an iron and aluminum foundry we built a pattern for an aluminum part of a specific alloy( i forget which one) that was supposed to shrink .25in per foot. aluminum is known for shrinking alot but that day and that batch of aluminum, there was no shrink. the part ended up being .5in too big.

point is , there can be considerable variations in cast parts despite the best efforts of the people making them...hence your different drillings on what are essentially the same part.

the thing to do would be to see how they balance on their own.

scott

Hhmmmm...

So if I understand you correctly, what you are saying is that with the variations in drillings between units there was an attempt BEFORE installing pulleys and flywheels on the motors to balance all of the flywheels and all of the pulleys to within a prescribed spec before mounting them on the engines...?

JJ,

I think that is the case (what MR2 Zig said). From a manufacturing point of view I think it is impractical to balance the whole assembly specific to each engine. My bro used an SZ crank pulley on his 75 for the longest time, no problems at all.

i bought one of peters flywheels on ebay... and although it hasnt made it on the car yet i will be taking it to a balancing shop. The flywheel is billet aluminum and has no recessing like the stock flywheel, not even a drill mark. SO i think it is implicitly zero balanced w/o being advertised as such.

MR2 Zig wrote:JJ,

having worked in pattern shops (part of a foundry) i know that depending on the casting method, the make up of the material, the day, and which side of the bed the foundryman got up on that day, one pattern will make castings that weigh differently. also the gates and risers get changed sometimes and that will have an effect also.

when i worked for an iron and aluminum foundry we built a pattern for an aluminum part of a specific alloy( i forget which one) that was supposed to shrink .25in per foot. aluminum is known for shrinking alot but that day and that batch of aluminum, there was no shrink. the part ended up being .5in too big.

point is , there can be considerable variations in cast parts despite the best efforts of the people making them...hence your different drillings on what are essentially the same part.

the thing to do would be to see how they balance on their own.

scott

I'm sorry but I just can't get that hilarious way of describing shrink, inch per feet!
What's wrong with a percentage?

MAts: probably because it woul be 4.1666667%

......easier to say .5 inch per foot......10 times a day...