Mounting A 2.5l Flywheel To A 3.0l??

5307 Views 26 Replies 7 Participants Last post by Alfar7, Dec 8, 2007

Barbalatte

Discussion Starter · Nov 18, 2007

Hi guys,
Is it possible to adapt my 2.5L flywheel to my 3.0L engine. Keeping in mind I want the starter motor to still work. What mods need to be done.

Thanks

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Gabor K.

· #2 · Nov 21, 2007

Yes, have done that! Installed 3L 164 in GTV6 with the GTV flywheel. A condition is that the whole crankshaft, front pulley and the 2.5 flywheel is balanced together as a unit. That means pulling apart the whole engine. In our case the imbalance before balancing was 30grams while tolerance was 15grams. After balancing the imbalance was under 1 gram. This engine is very smooth!
Have seen from other projects that the 2.5L flywheel was mounted without balancing ,taking chance that it would work. But i wouldnt recommend it from own experience.
A way to avoid all the dismantling and balancing of all the rotating parts could be to find out what imbalance it was with the 3L flywheel and then to balance the 2.5 fl.w. to same imbalance. Then theoretically one would restore the same balance as the factory engine. Not ideal solution but could work in my opinion...
We used a 4mm spacer between 2.5 flywheel and engine.
Hope this will answer your question!

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Alfar7

· #3 · Nov 21, 2007

Flywheels

A way to avoid all the dismantling and balancing of all the rotating parts could be to find out what imbalance it was with the 3L flywheel and then to balance the 2.5 fl.w. to same imbalance. Then theoretically one would restore the same balance as the factory engine. Not ideal solution but could work in my opinion...

In reality the late 2.5 & 3 liter flywheels are the same. The balance drill holes were to balance the flywheel only to the correct counterweight offset & position before installation. Same for front pulley.
Engine ballancing , other than matching Piston, Rods, and Rod Big end weights is really a process of guessing what counterweights (bob weights) to use, as regardless, the engine is only truly balanced at one RPM in the spread.
It`s over rated unless you are balancing for 7000 RPM and the balancer probably does not have a clue to accurately calculating bob weights to do so.
If you are going to lighten a flywheel, have the shop measure amt. and location of counterbalance built in at the factory, and after cutting, return the amount of out of balance to the same position & amount.

I remind you that a lot of bull**** has become "holy grail" to Alfa Owners by comments made by the truly uninformed.

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Gabor K.

· #4 · Nov 21, 2007

? Did I write something wrong, actually, or did you miss some of my points. Richard?

Barbalatte

Discussion Starter · #5 · Nov 21, 2007

Thanks for the help guys.
I have decided for the moment to fix the 3 Litre flywheel. It wasn't badly damaged anyway. See how we go.

Alfar7

· #6 · Nov 21, 2007

Geez

Did I write something wrong, actually, or did you miss some of my points. Richard?

Actually if you go back & read your post, yes, you did mis-speak.
1) the late flywheels are the same
2) the engines are balanced individual parts, not as a unit.
3) I attempted to put the balancing myth in perspective.

Gabor K.

· #7 · Nov 22, 2007

Well OK, you made your point.
I was referring to 12V engines. I dont know about the 24V engines if you mean late by that. As I referred to this in another thread the 2.5 and 3.0 12V flywheels have different part number and also different balancing, as I know, and cannot be directly interchanged.

2. As late as a year ago the whole crank/pulley/flywheel unit had to be rebalanced when changing from 164 3L flywheel to 2.5GTV6 fl.w. As you noticed the unit was way out of tolerance.

3. balancing the whole unit is still recommended, here at least, to get a good result and long lasting engine.

Barbalatte

Discussion Starter · #8 · Nov 22, 2007

OK. You guys have succeded in confusing me.

So a 12v 2.5 Litre and a 12v 3 Litre Flywheel have the same balances? Is this correct? Because I've swapped my 12v 2.5L to a 12v 3L.

Not a 164 3L. A 75/Milano 3L.

Gabor K.

· #9 · Nov 22, 2007 (Edited)

Barbalatte: If you study the front pulley and the flywheel properly, you will se there is an inbuilt counterweight which is there to counterbalance the cranckshaft. The stroke on the 2.5L and the 3L is different and therefore the counterbalance needed in the two engines is a bit different. Therefore its not advisable to interchange these flywheels. Of this same reason when lightening the flywheel, two different flywheels have to be offered to cover the two engines. Look at offers from Performatek.

deDion Drive Line

Some drawings showing the counterweights in pulley and flywheel.

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3

Alfar7

· #10 · Nov 25, 2007

2.5 & 3.0 flywheels

--------------------------------------------------------------------------------

After 1987 the 2.5 & 3.0 flywheels were the same for the 119 model cars, both offset & counterweight. Each flywheel is balanced as a unit as is the front pulley. They are used as they are grabbed from the pallet. Don`t use a gtv6 unit with the 3.0.
__________________

Gabor K.

· #11 · Nov 25, 2007

Really Richard, you are making some confusion here. Anybody who can confirm this, my info does the contrary!

119 series here is the Alfa 6. GTV6 being 116 series and 75 being 162 series. The 75 had both 2.5 and 3L engines. I have the spareparts catalog for this model engine and the numbers for 2.5 and 3L are different! How could they have been from the same bin? Also my catalog is from sept. 88..

I agree however that you cannot use the GTV6 fl.w. on the 3L engine(without due balancing), but that has been my position all along.

Alfar7

· #12 · Nov 25, 2007

flywheels

GABORK:
You must be a freaking ENGINEER!

I`m talking about the Milano 162 B6 type for God sake!.. Sorry for the typo.

Use my info or ignore it.

Gabor K.

· #13 · Nov 25, 2007

Sorry for that Richard, I had to clarify what you meant

, I am sure you know lot about engines since you are into camshaft production.

I found an interesting article about crankshaft balancing which could have general interest. The alfa V6 engine is an externally balanced engine.

Engine Balance

fiatosca

· #14 · Nov 26, 2007

A GTV/6 flywheel on a 3.0 will need a spacer on the flywheel (my brother did it to his and it works fine). A 2.5 Milano flywheel works fine on a 3.0 engine as I have done this very thing. When I performed the swap I was concerned because of all the BS out there regarding this issue. I was told that the 2.5 unit was heavier than both the 3.0 and GTV/6 units (unsubstantiated). I was also told that 2.5 motors had fewer grams of counterbalance weight than the 3.0 (again unsubstantiated) so I put my 2.5 front pulley on the motor just for good measure. Car has performed flawlessly for 7 years.

Barbalatte

Discussion Starter · #15 · Nov 26, 2007

Thanks for all the 'confusing' info. guys.

I am in the process of getting my engineer to fix the 3 litre fl.w. anyway.
One of the 3 screw supports was cracked. He is going to re-build that stump.

Gabor K.

· #16 · Nov 26, 2007 (Edited)

Fiatosca: You actually admit that you don´t know the amount of unbalance you drive around with, since you just changed without checking! Well. as I pointed out earlier here we have checked and there was an unbalance way out of tolerance when changing from 3L to 2.5L fl.w. ! That you can live with your results does not mean that its the right way to recommend others to do it! Referring to Guy Croft, the engine expert, you can live with some unbalance at everyday low revs, but pulling high revs could ultimately rip off your flywheel!

Checked with our balancing company:
Normal factory tolerances for unbalance: 15grams, some as low as 5 grams. (we experinced 30g unbalance when changing from 3L to 2.5L fl.w. Had we not balanced it would have reduced engine life).
Unbalance normally felt from 50grams but only at resonant rpm.
Difference between 15g and 50g unbalance is 300.000km vs 100.000km bearing life.
They completely agreed with Guy Croft that an engine working well with unbalance at everyday life could rip off the flywheel at high rpm at trackdays. So if there still is scepticism about the necessity of balancing, please contact your local good quality engine company and ask for guidance!

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fiatosca

· #17 · Nov 27, 2007

Gabor K. said:
Fiatosca: You actually admit that you don´t know the amount of unbalance you drive around with, since you just changed without checking! Well. as I pointed out earlier here we have checked and there was an unbalance way out of tolerance when changing from 3L to 2.5L fl.w. ! That you can live with your results does not mean that its the right way to recommend others to do it! Referring to Guy Croft, the engine expert, you can live with some unbalance at everyday low revs, but pulling high revs could ultimately rip off your flywheel!

Checked with our balancing company:
Normal factory tolerances for unbalance: 15grams, some as low as 5 grams. (we experinced 30g unbalance when changing from 3L to 2.5L fl.w. Had we not balanced it would have reduced engine life).
Unbalance normally felt from 50grams but only at resonant rpm.
Difference between 15g and 50g unbalance is 300.000km vs 100.000km bearing life.
They completely agreed with Guy Croft that an engine working well with unbalance at everyday life could rip off the flywheel at high rpm at trackdays. So if there still is scepticism about the necessity of balancing, please contact your local good quality engine company and ask for guidance!

So that must be the cause of all those exploding GTV/6 flywheels I've heard so much about! I would imagine that a motor which is so out of balance that it is set to shed it's flywheel might first exhibit some sort of vibration. Mine is smooth as silk so I'll sit tight for now.

Gabor K.

· #18 · Nov 27, 2007

You know well what part applied for your case, so don´t try that !

chelo

· #19 · Nov 27, 2007

Very interesting topic. Yes any engine builder would suggest getting your engine balanced. What if your engine was healthy to start with and just want to change flywheel or say pulley for example. I don't want to get off topic here but what about changing just the front pulley? My milano is a 3.0 verde. Can I just put a 164 60-2 teeth front pulley?

Alfar7

· #20 · Nov 27, 2007

What???

Thanks for all the 'confusing' info. guys.
I am in the process of getting my engineer to fix the 3 litre fl.w. anyway.
One of the 3 screw supports was cracked. He is going to re-build that stump.
__________________

Barbie!!
Don`t let that **** happen! Replace it!

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