Harmonic balancer / Torsional Damper Confuzzlement (Page 1/1)
PK JAN 05, 02:20 AM
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 http://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
olejoedad JAN 05, 11:38 AM
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.
Gall757 JAN 05, 11:44 AM
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.
PK JAN 05, 12:27 PM

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.
fieroguru JAN 05, 02:26 PM
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).]

PK JAN 05, 03:41 PM
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!
fierogt28 MAY 30, 09:10 PM
I want to add some information on this subject with visual evidence of the 85-86V6 balancer and the 88V6 balancer.

The issue is and would need input on the validation of the 85-86V6 balancer.

I know for sure that the 88V6 balancer I have is accurate. (a true 88V6 fiero balancer)

The reason I need validation on the earlier balancer is I have a reason to believe it is for another GM V6 engine.

You can see I put the balancers in the same clocked position with the crankshaft keyway and the true groove timing mark
at the 12 o clock position for reference.

You clearly see the crankshaft keyway is totally off, way off as the 88V6 balancer. Unless I'm wrong, please confirm.
Both balancers are really nice shape, in fact the 85-86V6 balancer is a NOS unit. I was told it was new and looks like it
was just painted and installed, but not used. Just sitting for years. I have the new GM box, but I have a feeling its not a true
85-86V6 fiero balancer.

This is what I want to clairify with others with their originals if you have photos to prove it.


85-86V6 balancer.
Front side.


Rear side. (You can see the weight boss, like others have mentioned)


88V6 balancer
Front side.

Rear side (no weight boss)


If anyone can pitch in, that would be great.
And just trying to help others with these vintage parts with picture, not just words.

Thanks,

------------------
fierogt28

88 GT, Loaded, 5-speed.
88 GT, 5-speed. Beechwood interior, All original.

fierogt28 MAY 30, 09:23 PM
I forgot to add, I have a pre-88 fiero V6 engine in one of my cars now, with another GM balancer
for the 80s era. I don't know which car, but the bigger timing mark are off from the fiero original balancer.
Car runs excellent, just found out that because upon timing the engine, the timing light and balancer degree
indicator bracket, as the groove just didn't match.

I did find the spot at #1 cyl and marked it on the balancer for a new reference.

The distributor was way off, and more counter-clockwise than where the distributor is normally.

The ICM is usually about at 8 o clock position stock, but mine with this balancer the distributor
was at 6 o clock position if you look at the engine from the rear. (at the correct timing setting)

I could confirm if my balancer is the same as my example picture in my last post once my engine
is out of the car some day.

Thanks,

------------------
fierogt28

88 GT, Loaded, 5-speed.
88 GT, 5-speed. Beechwood interior, All original.

fierogt28 JUN 12, 10:26 PM
Has anyone looking into this or found the same finding in my last post?

It would confirm my pre-88V6 balancer is incorrect for the Fiero application.

Thanks,

------------------
fierogt28

88 GT, Loaded, 5-speed.
88 GT, 5-speed. Beechwood interior, All original.