Hello PFFers,

I am trying to understand why some harmonic balancers have a lump of metal "weight" on the back located by keyway.

This thread https://www.fiero.nl/forum/A...110502-2-104579.html has lots of information and shows pictures of the "weight" I am referring to.

Damper doctor suggests:

Internally balanced enjun = no HB weight

Externally balanced enjun = yes HB weight.

This is not the case as TK reports in that thread that he has an 86 (externally balanced) with no HB weight. I have an 86, no HB weight.

The GM article clipped in that thread suggests that it matters not internally/externally balanced enjun = neutrally balanced harmonic balancer...... But then includes a picture of the harmonic balancer with the "weight".

So as someone with a delaminating harmonic balancer, damper doctor would supply me with a HB with weight (based on the linked thread info) which is NOT what it has at the moment and not what other 86 owners have reported. And if the GM article is correct then ALL V6 HBs are neutrally balanced.... And it doesn't make any difference which is fitted.

Confused much! Does it matter if HB has that weight or not?

Would be interesting to know date of cars and if HB with/without weight to see if that helps clarify anything!!

Cheers
PK

For what it's worth, the P22 shows the same part number for all years of the Fiero 2.8.

P/N 14102508

The same diagram shows two part numbers for the crankshaft, 88 is different from 85-87.

I think this is a case where it does not matter. When new, the balancer is no doubt a purchased part and various vendors built them various ways, making slight modifications to the casting for any number of reasons. We would have heard a lot of complaining by now if balancers did not function well on certain year engines.

quote Originally posted by olejoedad: For what it's worth, the P22 shows the same part number for all years of the Fiero 2.8. P/N 14102508

As TK mentioned later in 22p it then says:


85-86 Damper, Tors 10032616
87-88 Damper, Tors 10044956

So even the 22p can't agree with itself!

Rodney mentioned that damperdoctor ground off the weight on the harmonic balancers that he ordered.... So they must think there is some difference.

I have found an OEM replacement balancer but unlike mine, it has the weight and I really have no idea if this is suitable.

You have the as cast geometry, but then after being machined to spec and assembled, the balancers are balanced to spec (neutral or with some imbalance) normally by drilling additional holes along the outer perimeter, but I have seen people mill of cast in weights as well.

With it being such a small as cast boss, and as purchase volumes declined, they likely chose to use one standard casting (possibly with the boss) to save on mfg cost and just balance them as needed to meet the appropriate spec (neutral or with an imbalance)

Even in the picture in the article where they refer to the balancer as being neutral balanced, you can see the boss, but you also see the balance holes on the same half of the balancer as the boss, which likely helps make it neutral balanced.


The amount of imbalance you introduce is the mass of the weight (or lack of weight = hole) x the distance from the crankshaft center-line. So with this very small boss being a couple of inches from the center of the crankshaft, the imbalance it creates is very, very small.

To put the potential imbalance into perspective, the 400 SBC was externally balanced at both the balancer and flywheel. Look at the size of the weight inside the balancer for it. It could easily be 50 times larger than the tiny boss on the 2.8 one.


So for the 2.8, buy the balancer from a reputable supplier for your specific application and move on...

[This message has been edited by fieroguru (edited 01-05-2019).]

Thank you for the detailed reply guru. I have no idea how critical an imbalance would be.

What I didn't want to do was spend a lot of money to ruin my engine!