Notices
928 Forum
Sponsored by:
Sponsored by: 928 Specialists

Harmonic Balancer differences

 
Old 03-20-2016, 05:07 PM
  #1  
Kevin in Atlanta
Addict
Rennlist Member
Thread Starter
 
Join Date: May 2002
Location: Roswell, GA
Posts: 5,149
Default Harmonic Balancer differences

Specifically, what are the differences between the 90- and let's say the 87. Besides the color change? The 90 I am putting back together came with an orange one and wonder if I need to find a black/gray one.
Kevin in Atlanta is online now  
Old 03-20-2016, 05:39 PM
  #2  
Rob Edwards
Archive Gatekeeper
Rennlist Member
 
Rob Edwards's Avatar
 
Join Date: Sep 2002
Location: Irvine, CA
Posts: 13,683
Default

Black is GT only, AFAIK. Go with the orange one.
Rob Edwards is offline  
Old 03-20-2016, 06:40 PM
  #3  
Doug_B_928
User
 
Doug_B_928's Avatar
 
Join Date: Jul 2011
Location: Winnipeg, Canada
Posts: 906
Default

Early cars also have black HBs (at least my 79 does).
Doug_B_928 is offline  
Old 03-20-2016, 07:26 PM
  #4  
Kevin in Atlanta
Addict
Rennlist Member
Thread Starter
 
Join Date: May 2002
Location: Roswell, GA
Posts: 5,149
Default

Interesting. The 90 also came with the smaller diameter a/c pulley.
Kevin in Atlanta is online now  
Old 03-20-2016, 08:27 PM
  #5  
GregBBRD

Rennlist
Basic Site Sponsor

 
GregBBRD's Avatar
 
Join Date: Feb 2005
Location: Anaheim
Posts: 9,792
Default

I think it was so they could identify the engines on the upper storage racks, without climbing around and looking at the paperwork.....

Seriously, the GT dampers are stamped differently. Perhaps the balance was held to a tighter tolerance, because of the higher rpms?

It's probably all a moot point, now that the rubber between the two layers is rock hard. The vast majority of the dampers quit "absorbing" harmonics years ago.

I consider all of them to be equal junk, at this point in time.
__________________
greg brown




714 879 9072
[email protected]

If the kids keep breaking a crowbar in the sandbox, sometimes it is easier to just give them a stronger crowbar, instead of trying to figure out what they are doing in the sandbox.
GregBBRD is offline  
Old 03-20-2016, 08:29 PM
  #6  
GregBBRD

Rennlist
Basic Site Sponsor

 
GregBBRD's Avatar
 
Join Date: Feb 2005
Location: Anaheim
Posts: 9,792
Default

Originally Posted by Kevin in Atlanta View Post
Interesting. The 90 also came with the smaller diameter a/c pulley.
I believe you will find out that the automatics came with the bigger diameter A/C pulley, because they "search out" high gear before they get across the intersection and thus need to operate the A/C at lower rpms.
__________________
greg brown




714 879 9072
[email protected]

If the kids keep breaking a crowbar in the sandbox, sometimes it is easier to just give them a stronger crowbar, instead of trying to figure out what they are doing in the sandbox.
GregBBRD is offline  
Old 03-20-2016, 08:29 PM
  #7  
Daniel5691
Addict
Rennlist Member
 
Daniel5691's Avatar
 
Join Date: Jun 2014
Posts: 2,423
Default

Is there an updated HB available, one that still does some dampening?

Thanks,
Dan
Daniel5691 is offline  
Old 03-20-2016, 10:02 PM
  #8  
Rob Edwards
Archive Gatekeeper
Rennlist Member
 
Rob Edwards's Avatar
 
Join Date: Sep 2002
Location: Irvine, CA
Posts: 13,683
Default

Best bet is an ATI with a custom hub- Greg has 'em for his strokers.
Rob Edwards is offline  
Old 03-20-2016, 10:16 PM
  #9  
JWise
Addict
Rennlist Member
 
JWise's Avatar
 
Join Date: Dec 2003
Location: Oklahoma
Posts: 2,564
Default

Originally Posted by Rob Edwards View Post
Best bet is an ATI with a custom hub- Greg has 'em for his strokers.
I need to check with Greg and see if he could spec one for my mildly modded 90GT (Motorsport X, Bosch 24lb injectors, Sharktuned by Colin - future plans include Greg's headers/exhaust). Would be happy to purchase from him and have Sean do the install.
JWise is offline  
Old 03-20-2016, 11:45 PM
  #10  
GregBBRD

Rennlist
Basic Site Sponsor

 
GregBBRD's Avatar
 
Join Date: Feb 2005
Location: Anaheim
Posts: 9,792
Default

I do keep custom hubs and ATI dampers in inventory.
GregBBRD is offline  
Old 03-21-2016, 07:07 AM
  #11  
FredR
Addict
Rennlist Member
 
FredR's Avatar
 
Join Date: Jun 2005
Location: Oman
Posts: 5,880
Default

If by now non of them work as they were originally intended to what should we be looking for in terms of symptoms indicating such?

Given they dampen harmonic vibrations presumably there will be a specific rpm point where such vibrations will manifest themselves noticeably so given all engines of a specific type are the same. Whether S4's, GT's and GTS's have a different resonant frequency would be interesting to know.

Rgds

Fred
FredR is offline  
Old 03-21-2016, 09:15 AM
  #12  
928S MN
Addict
Rennlist Member
 
928S MN's Avatar
 
Join Date: Aug 2015
Location: Lakeville, Minnesota
Posts: 332
Default

Very interested in the outcome of this post as I'm close to pulling the HB on my 1985 928S for the TB/WP job.

Anyone have an approximate price range for a "new" HB?

If the harmonics are not absorbed, how does that show up in terms of engine damage? Lost performance?
928S MN is offline  
Old 03-21-2016, 09:43 AM
  #13  
Sapientoni
User
 
Join Date: Jan 2015
Location: North Carolina
Posts: 76
Default

Steel Rubber Products does restoration of motor mounts etc and would probably restore it
Sapientoni is offline  
Old 03-21-2016, 12:41 PM
  #14  
GregBBRD

Rennlist
Basic Site Sponsor

 
GregBBRD's Avatar
 
Join Date: Feb 2005
Location: Anaheim
Posts: 9,792
Default

Originally Posted by FredR View Post
If by now non of them work as they were originally intended to what should we be looking for in terms of symptoms indicating such?

Given they dampen harmonic vibrations presumably there will be a specific rpm point where such vibrations will manifest themselves noticeably so given all engines of a specific type are the same. Whether S4's, GT's and GTS's have a different resonant frequency would be interesting to know.

Rgds

Fred
I've seen a huge increase in main bearing wear and movement/fretting of the cradle on the block, over the years, which I attribute to a decrease in harmonic absorbtion. I used to take a look at rod bearing wear and be assured that the main bearings would still be nearly perfect. Not any longer. I'm seeing some engines with very nice looking rod bearings and badly damaged main bearings....which I can only attribute to wear from increased harmonics.

I've also cured several chronic engine vibrations which nothing else anyone tried could cure, by changing the damper.

I believe that damage from unabsorbed harmonics is probably a progressive long term problem, not something that will kill an engine or cause drivetrain damage in a few days (or months) of normal driving. However, I also believe that if one was to load and hold an engine at the peak of its harmonics (like they certainly did when testing) destructive damage certainly would occur at a quicker rate.

I also question the sanity of the current trend to remove the harmonic absorbtion device in torque tubes. That is, for the majority of vehicles, a different topic. Howwever, for the vehicles that were not equipped with this device (like the GT models), I believe that a front damper in very good condition is paramount.

And who really knows?

Perhaps the different colored GT front dampers (which this thread was about) were different because of the removal of the torque tube harmonic damper......
GregBBRD is offline  
Old 03-21-2016, 05:00 PM
  #15  
dr bob
Chronic Tool Dropper
Lifetime Rennlist
Member
 
dr bob's Avatar
 
Join Date: Oct 2001
Location: Bend, Oregon
Posts: 17,840
Default

Greg is spot-on (as usual...). The damper limits the 'ringing' that happens due to the different twisting forces on the crank as different cylinders compress and expand. Failure mode from that 'ringing' includes whorling of the oil film on main bearings and susequent wear from the failed oil-film dam. Longer-term, you'll discover the fatigue life of the crankshaft itself.
dr bob is offline  

Thread Tools
Search this Thread
Quick Reply: Harmonic Balancer differences


Contact Us - About Us - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: