Slalom4me

Someone who works on GMs for a living and
was under my car recently mentioned that
the outer ring on the harmonic balancer appears
to have slipped a few degrees.

We documented the present position with witness
lines and I'll be checking it periodically for signs of
further changes. When I make time, I'll check it
against actual TDC of #1 cyl.

An inexhaustive search brought back instances
where LT1 balancers have caused troubles but no
examples of L98s slipping.

Drivetrain is essentially stock. HB has not been
removed during my six years of ownership and
I'm unaware of any reason for it to have been pulled
previously.

Thanks,
Ken R.

65Z01

I had that happed to the damper on my '86 IROC LB9 engine. The rubber between the inner and outer rings had deteriorated to such an extent the the outer ring slipped by quite a bit and even moved backward somewhat.

It hasn't happeded yet on the Vette but in time I expect it will.

Brimis

I had the same problem on my 84 and replaced the harmonic balancer. I believe the L98 is different then the L83.

kize

This has happened to me first hand. Couldn't figure out why my timing marks where off but car ran great. Thought some bone head had put the Dist in wrong- but plug wires hadn't been moved. Balancer had moved about 25 degrees off TDC and moved back off center hub. I was shocked - still spun true but had slight vibration(out of balance). Go figure

CFI-EFI

Check those "witness lines" frequently. At the first confirmation of movement, replace the damper, immediately. The L98 damper is the same or similar to all SBC (and other) dampers since they've been using the elastomer. They are a common replacement item and you will find one at most parts stores. The reason to get it off of there, ASAP isn't for checking your timing, but for your safety and of those around your car. If it comes loose, that outer ring may break or work is way off of the hub at any time. Depending on where you are, your luck, and your rpms, that damper can go almost anywhere. It could wipe out your trans cooler lines, your radiator hose(s), your radiator, it could end up coming up through your hood, or hit the pavement just right and take out a tire or two, causing you to lose control of the car. Usually, things don't get that dramatic, but the potential for disaster is there. A word to the wise...

RACE ON!!!

rrubel

Mine started slipping after my engine was rebuilt; wondered why it wasn't staying in time. I replaced it with another stock one, but have heard since that they will start breaking again if run over 5500 RPM. I'm now considering a Fluidamper or similar.
[RICHR]

Slalom4me

This is enough to confirm my first inclination
which is to just replace the thing. Balancers
are inexpensive and easy to R&R. As CFI-EFI
notes, the consequences of a failure have
a high likelyhood for property damage and
injury.

In fact, I was going to change it out for a
Fluidamper a couple of years ago when I
was looking for ways to reduce rotating
mass. However, in looking into the matter
I came across David Vizard's view that the
HB is not an item to cut weight on and so
I left the OEM HB in place.

I'm interested on the current view about HB
weight but will start another thread.

Thanks to everyone for the replies.

Slalom4me

When the parts person gasps, you know you better
prepare for the worst.

I stopped in at the dealership this AM to pick up
some items and get P & D on a replacement damper.
Having become acquainted with prices at Superior
and SDPC, I wanted to know what the '89 L98 pn#
is and the local price.

Imagine my bemusement at the parts person's
reaction when he looked it up and found that trade
for pn #10128489 is about $650 USD.

This is the direct L98 replacement part. In comparison,
the #24502534 High RPM (9,000) Torsional Damper
is listed by Superior for $229 - a much different piece.
More conventional performance dampers can be had
for well under $100.

The OEM price sure tips the scales in favor of a
Fluidampr ...
.

65Z01

Indeed Summit sells the OEM style damper for ~$60.

Rick86

My original harmonic balancer slipped backward and knocked a hole in the timing chain cover. It did this with about 110,000 on the clock.

Slalom4me

Thanks for the info, I went there and can see the
"SUM-161350" 6-3/4" non-SFI w /basic timing marks.

Also see their "SUM-B64265" 6-5/8" SFI approved,
partially degreed piece for $200.

(Of course the Fluidampr's pop up in the search, too.)

Regards

Frizlefrak

So did mine, but I got lucky....just took out the crank seal. Oh well, was a good excuse to change the timing chain.

Don't drive the car like this. WHEN (not if) it disintegrates, all Hell can break loose. The aftermarket balancers are reasonable.

Rick86

I believe my replacement was a Pioneer that I ordered from one of the chain parts stores. The Pioneer is made is Australia. Did some searches on the forum and that is what was recommended. I also put one of those harmonic balance covers on. Its mostly for cosmetics, but its degreed and attaches with the three harmonic balancer bolts, its also keyed. Now I have my H/B degree 0-90 then every 90* after that.

tjwong

You can have yours rebuilt for about $75 plus shipping. I have had these done before by a company called Damper Dudes in Redding California. Excellent quality and better than new. They use a elastomeric compound 10x stronger than what the General used. I use them to fuse my LTx blower balancers together. If they last with a cogged belt blower balancer you can bet that they will last in a stock application.

http://damperdudes.net/

Oh, I forgot to mention. Turn around time is very fast as well.

Red Tornado

when i had my engine rebuilt/upgraded, the harmonic damper was one of many items that i had replaced as a "while you're at it" scenario, given it had 66k miles on it........purchased an OE upgrade thru www.cnc-motorsports.com (their ebay store), a Professional Products 6 3/4" damper which was about $52.