that harmonic balancer i bought...

[cc]

Hi
The bought one from alfaworkshop in the UK isnt identical to the original. : )
I didnt pay too much attention to the website when ordering... and the text under the parts pic detailing that it was also suitable for the 3.2L didnt raise any alarm bells.

Was wondering what members thoughts on this.
Wouldnt the different masses of pistons conrods and crankshaft between the 2.5 and the 3.2 mean that one balancer doesnt fit all?

Ive bought a replacement balancer as the internal rubber distorted significantly when I was taken the old one off.

See the pics.
Also bought a timing belt kit. The new belt seems a different length to the old... Will count teeth and measure later.
cheers

[bazzbazz]

If you have bought all items from the Alfa Workshop site then you can be assured that you Do have the right ones. The Balancer is correct for both the 2.5 & 3.2 V6.

The belt should be 185 teeth x 28mm wide. It should be written on the belt somewhere.

[cc]

thx Baz. Will do some measurements when i find the vernier.!
The new one also feels a little heavier.

Any thoughts on the in built weight balance. Was wondering on its function when the internal rotating parts, crankshaft etc  should be balanced. Wonder what its balancing.

[bazzbazz]

Basically it compensates for the shock of the piston being fired back down the bore against the crankshaft, thus reducing vibration

[Craig_m67]

My understanding is the harmonic balancer, clutch and flywheel are all zero balanced so they can't upset an existing donk when fitted... I've been known to be completely wrong before however 

[cc]

thats what i thought*2 also..
i read in a motorbike magazine in the dim past that different cylinder configurations eg v twin, single, parallel twin and the relative piston motion sets up harmonic vibrations not necessarily in the plane of the pistons motion.
Still scratching head on why the H.B. has an offset mass casting. Will ask a local engine engineering firm.

[105gta]

CC, the balances are different for all 3 engine sizes. As you suspected yes the counter balance is different to suit the different piston weights and different throws of the cranks shafts. You will also notice that the balancer for the 3.2 has an extra ring pressed onto its outer band to resonate at a different frequency.
Although it will physically fit your 2.5 it WILL be out of balance for your engine.
The results could range from minor vibration(unlikely) to fairly noticeable vibration which over time will excessively wear the main bearings. And I suspect the balancer itself will fail prematurely.

[cc]

!!! will see if I can order an original thru an alfa dealer. The spare place in SA were nil stock.

[bazzbazz]

Read the add guys.

https://www.alfaworkshop.co.uk/parts/156_Pulley.shtml

"Special Note: 2.5v6: Will also fit 2.5 and 3.0 as a substitute part"

Do you really think Alfa Workshop of all places are going to sell a Substitute part "just because it will fit"?

CC, may I suggest you email your query to Alfa Workshop, they will reply within 24-48 hours and I am sure their reply will put you at ease. Lets not go spending your hard earned cash when you don't have to.

And to get your brains thinking - Many companies manufacture Light Weight crankshaft pullies, not just for Alfas, but most cars, so if the weights are drastically different, why do they not cause trouble? (Hint - Think Dynamically) 

And CC asked - "Still scratching head on why the H.B. has an offset mass casting" It's a V6, not a straight inline.

I should point out that Harmonic Balancers are there to balance out the harmonic frequencies of the torsional reaction loads of the engines operation, not balancing as in counter weight.

I am terrible at explaining things like this in my own words, hopefully this link may help people to understand better as to what they do.

http://www.agcoauto.com/content/news/p2_articleid/273

[bazzbazz]

As you suspected yes the counter balance is different to suit the different piston weights and different throws of the cranks shafts.

To my knowledge the crank on the 2.5, 3.0 & 3.2 are all the same, correct me if i am wrong.

You will also notice that the balancer for the 3.2 has an extra ring pressed onto its outer band to resonate at a different frequency.

Not sure what your referring to here, what extra ring?

[105gta]

Is there a side note to that?
As there should be!

As for aftermarket lightweight pulleys yes they are available but meant for certain applications. And most engines are internally balanced as in each item is dynamically balanced on its own.
Our busso v6's are not!
As you can see in the pics provided, the 2.5 balancer has a counter weight a little over 120drg of the inner dia that has been drilled significantly as is most 2.5 balancers, yet the 3.2 balancer not only has a larger counter weight. It it also has 3 slugs of Mallory metal added. To increase the imbalance even further to suit the 3.2 internals.

CC if that is your current 2.5 balancer in the pics then I don't see any real issue with it unless it looks really bad on the back face. The busso balancers don't seem to give trouble. I'd be inclined to re use your original otherwise have someone inspect it for you if you're not sure.

[105gta]

Bazzbazz all 3 engines 2.5,3.0and 3.2 have different cranks. Different stroke lengths.
Hence the difference in the balance
The ring I refer to is the shiny section that the little sticker that denotes 3.2 is on. The 2.5 and 3.0 don't have this the 3.0 has minimal drillings, he 2.5 has many and the 3.2 has extra weight added.
All the same base casting but then modified to suit each application.

[johnl]

A long time ago I did some research on harmonic balancers. From what I dimly recall, the ideal 'balancer' would be a solidly mounted mass fitted to the front of the crank that mimicked the mass of the flywheel (and clutch) fitted to the other end of the crank. Since this is impractical, a smaller mass rotational damper is commonly fitted, but with some freedom of motion between the crank and the mass, as provided by an elastic rubber insert. This causes the balancer mass to rotationally oscillate in reaction to the oscillations of the crankshaft, and act as if it were a somewhat larger mass, up to a point. I'm fairly sure this is an over simplification, and I'm not sure of the physics behind it.

Assuming this recollection is correct, then any rubber mounted mass (that is smaller in mass and radial displacement than the flywheel) will oscillate in a maner that to some extent mimics the damping effect of the larger mass of the flywheel at the other end of the crank, and be better than no harmonic balancer. I suspect that no harmonic balancer does this with 100% effect, i.e. that the size of the balancer is a compromise between effect, packaging, and increased rotational inertia.

The bigger the better, probably, but it has to fit, and not be so heavy that it excessively slows down responsiveness. Fitting a lightweight balancer will increase responsiveness, and 'free up' some power (as a lightweight flywheel will do), but the tradeoff is potentially more stress on the crankshaft...

Any balancer should be seperately balanced on its' own regardless of the other rotating parts (which should also be individually balanced), other than some old American engines perhaps (often the rotating parts were balanced as an assembly in old Detroit iron).

FWIW...

Regards,
John.

[bazzbazz]

CC if that is your current 2.5 balancer in the pics then I don't see any real issue with it unless it looks really bad on the back face. The busso balancers don't seem to give trouble. I'd be inclined to re use your original otherwise have someone inspect it for you if you're not sure.

I agree, looks fine to me, why were you replacing it again? Was there an issue with the key way or something?

[cc]

apologies for the poor pic quality.

The pic is oriented to show the different vertical height (new replacement is taller) and differences in drilled holes between the 2 HB's. The original has 5 empty holes and the replacement 3 filled.

The largest outside diameter for the original is 129mm and 139mm for the replacement.+- 1mm.
(still havent found my $2 plastic vernier: )

The part of the HB with the white sticker on it, on the replacement does appear to be fitted over the main body.

A bit like the starter ring gear on a minis flywheel. A family member many years ago heated said ring gear in the fire place to fit on the flywheel.

The original HB's internal rubber looks fine. Would hate for it to come apart tho if re used..!
The link in Baz's post shows which pulley puller not use : ) when replacing the HB.
Yes I used that one! So distorted the rubber in a way it wasnt designed to be.