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xrad
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Re: Balancing factor of the 3.0 12v?

Post by xrad »

WOW! now those are some fine replies!! Now I can go to a shop and at least have a good idea of what needs to be done for basic street use!

THANKS JK and !! Kterk !!

I did manage to find 3.0 fly and front pulley, and they are going onto a 12v S engine.
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Re: Balancing factor of the 3.0 12v?

Post by gran turismo »

I also saw somewhere where Greg Gordon had a 2.5 balanced to 51% with no vibration issues.

Just for further confirmation, after I had mine balanced I talked to another more experienced machinist who told me that virtually all V6 and V8 engines, even wierd ones like a VW VR6 are balanced to 50%-51%. And told me he would seriously question the 47% balance factor.

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Re: Balancing factor of the 3.0 12v?

Post by kevin »

Jim, surely the type or weight of oil does affect the rotational mass in your primary forces if some people assume 4grams while others assume 2 grams for oil on the v6. :wall:
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Re: Balancing factor of the 3.0 12v?

Post by Jim K »

Doing the calculation for using 2 or 4gr of oil on each end (reciprocating and rotating) will change the required counterweight by 2.5-3gr 'worst case'; changing BF by 1% will change the weight by ~7gr. Remember V crank balancing is a 'black art' and all procedures/percentages are empirical, the most definitive and serious method being the one used by Vibration Free, although not one that can be duplicated by machine shops.
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Re: Balancing factor of the 3.0 12v?

Post by kevin »

Thanks, Jim. My engines have all been balanced at 50% of recip weight. At least Im on the same page as you. Im starting to scratch my head on the dual mass flywheel I have on the spider 3.0 24v.
Did you notice any differences with later pulleys with the damper in compared to the old solid pulleys . I assume this only helps with harmonics in secondry forces ?
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Re: Balancing factor of the 3.0 12v?

Post by Jim K »

I've only balanced solid pulleys, but in the US a lot of V8 engines had (have?) damper pulleys. Haven't noticed any different procedures regarding this detail being handled in a special way. Now, about the dual spring-loaded flywheel, I don't know :?
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Re: Balancing factor of the 3.0 12v?

Post by Mats »

Dual mass flywheels are there to reduce torsional vibrations after the flywheel. And they are evil.
Shouldn't drive any different balancing procedures as far as I know.
Mats Strandberg
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Re: Balancing factor of the 3.0 12v?

Post by kterkkila »

I had a odd feeling for V6 cranks and confirmed that from EPER.. All the 3.0 V6 cranks, including 75, 164, new spider, RX, SZ and Lancia Thema, basicly all the engines with the old oil pump layout are replaced with the same crank, number 96412842. This means Alfa doesn't care about balancing factor. 24V got lighter pistons, thus I had 60% on my crank, while the same crank with 12V pistons could be near 50%.. Now I know all I need, end of the story. :evil:
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Re: Balancing factor of the 3.0 12v?

Post by Mats »

kterkkila wrote:I had a odd feeling for V6 cranks and confirmed that from EPER.. All the 3.0 V6 cranks, including 75, 164, new spider, RX, SZ and Lancia Thema, basicly all the engines with the old oil pump layout are replaced with the same crank, number 96412842. This means Alfa doesn't care about balancing factor. 24V got lighter pistons, thus I had 60% on my crank, while the same crank with 12V pistons could be near 50%.. Now I know all I need, end of the story. :evil:
Or it means you get the same part but it needs balancing. Very efficient way to cut costs, reducing part numbers that is.
Mats Strandberg
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-onemanracing.com-
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Re: Balancing factor of the 3.0 12v?

Post by kterkkila »

What says Alfa service manual about replacing cranks?
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