I am in the process of replacing the harmonic balancer on my 2000 Corvette (6 spd manual). I've read posts that discuss adding weights to the new HB to match what was originally installed on the vehicle, and that this is specific to manuals and not necessary for automatics. I've also read that Powerbond HBs do not require weights to be added.

I purchased a Powerbond HB (before I read about the weights), and it has the holes to place weights in the perimeter of the HB, which leads me to believe that they are required. Does anybody have a good understanding of this and know whether a not a Powerbond HB DOES require weights to be added to match the original HB?

 

 

Every damper has it's own unique balance signature. They are balanced at the factory independent of the crank to a certain specification.
Your new damper should be balanced to a similar spec from the manufacturer. I would recommend you not add any weights to it.

 

the balance weights are not intended to zero balance the damper itself.

Dampers are balanced by themselves at the factory, as stated above, before they are put on the engine. They will often have several blind drilled holes in them. That is for zeroing the damper alone, to some level of balance tolerance.

When the damper is put on the engine during the build process (along with the clutch and flywheel) additional weights are sometimes added to the damper, flywheel, or both as needed, to fine tune balance the entire assembly. This is to try to minimize vibrations felt in manual transmission vettes.

Your PB damper will be zero by itself to a certain degree (as was the factory original). You would still transfer the weights from your original damper, if you wanted to maintain the factory balance that you have had all along. There's a lot of misinformation about this, especially as it deals with flywheels. However, your FSM will tell you to transfer weights with respect to your damper when replacing with a new one.

However, I would guess that most people ignore that, and do not transfer any weights, and are fine. The radius in which the weights are placed is so small that balance correction from adding weights is pretty minimal. It's more pronounced at the flywheel locations.

So it probably won't matter whether you transfer or not. GM chose to add them during the final fine tune "hot balance process". It's your choice whether to maintain that or not.

FYI, if anyone doubts that GM does this external hot balance procedure, I can gladly provide numerous links to articles that describe it. There have been several articles explaining and walking through the build process.

Good luck.

and if you wanted to get real picky about it, you could always take off your current damper and check its state of balance. Then you could match your new one to it. That is in essence what you are trying to do when transferring weights, but without the guessing. Is it overkill? yes. Will anyone do that? probably not.

just remember, the dampers are zero balanced (to a degree) BEFORE any weights are added.

good luck

 

I wasn't aware that GM "hot balanced" the LS1 or LS6 engines.

I thought that was for the LS7.

 

yep, they did it for engines going to be used with manual transmission vettes. All LS1/6/2/3/7/9s that were going to mate to a manual transmission vette. Because of the split engine/transmission connected via torque tube. There is more written and documented about the LS7, LS9, and GS LS3 because those were hand assembled in Wixom. A lot written about that process. There are fewer written about the ones built in St Catherines.

the balance weights all serve the same purpose and were put on in the same manner during the same post assembly hot balance process.

But, the ones in the damper offer much less correction capability. And it is only "fine tuning" the whole assembly for minimizing vibrations. The engines are fine without them, it's just to minimize vibrations in manual vettes.

 

Very cool, great info!

I have about 30 years experience balancing crankshafts for High Perf engines. Given what I've seen, I still would not transfer the weights between dampers.

As you said, the best thing to do would be to take the old damper and the new one to a shop that does crank balancing. Have them spin the old one on a crank and zero out the crank with temporary weights, then spin the new one and make any adjustments to the new damper.

Honestly, a new damper will take a set between the interia and the elastomer ring after it has been rpm'd and run a while. I wouldn't bother with the A-B balancing until the new damper had taken a "set".

 

Excellent feedback. Thank you! I have to get the mounting bolt and a couple other parts yet before I put it all back together, so I figure I might as well get the weights to match the original balance. My next question is where can i get them. I dont think they can be removed from the original damper. They look to be pressed in to the holes. Will a GM service shop have them?

 

As I understand the stock balancer isn't keyed to the crank so how would you know where to put the weights on the new balancer compared to the stock balancer?

 

I'm fascinated by the technology, if you could post some links, I'd appreciate it.

T-Top Tom,

Good observation on the lack of key ways. Everything I work on is keyed, so I always forget the cheezy lack of keys on these things.

 

Fortunately I took a picture of the old balancer still on the crank, so I can tell where to add the weights on the new balancer. I just have to make sure I maintain the correct orientation when I install the new balancer. If I hadn't taken the picture I would be SOL!

 

Here is an old post that discusses matching the weights from an old to a new balancer. Excellent info as well;
http://forums.corvetteforum.com/c5-t...ight-info.html

 

I just realized I am SOL. The inner and outer hubs of my balancer have slipped, so I have no way of telling where the weights were relative to the crank. I guess I'll be 6 grams off. Fortunately, it doesn't sound like this will have any significant impact.

I guess the only way to know where your weights are is to mark your crank and note the weights relative to your mark BEFORE your harmonic balancer goes bad.

 

That link provided is very accurate about this. It tells you to mark or scribe the orientation of the balancer to the crank before removal. I've known of people being able to punch the existing weights out of their original balancer. You CAN order them, but you will have to provide the part numbers to the parts department most likely. When I researched all of this, I actually contacted close to thirty dealers across the country. I think one was actually familiar with the balance weights. Most had never heard of them, and when I gave them a part number, they were surprised when they popped up in the system. And this was dealing with the flywheel. Same weights are used in both however.

As mentioned, the radial placement of the weights on the balancer is much smaller than that of the flywheel weights, so imbalance correction capability is much smaller. Most people don't add or transfer the weights to their new damper, most new ones don't even have the holes to accept them, and they are fine. I would of course say to follow the book in this case, but if you can't put them in, you are most like going to be fine. Your engine is still fine, you just might feel some very slight new vibrations in the shifter, and then again, you might not.

I'll find all the links I put up about GM's process and put them here, for anyone curious about it.

 

http://forums.corvetteforum.com/c5-t...ion-twice.html

here is a link to another thread in this forum. A lot of the links to articles are in here, down a bit on the first page.

Most articles are about Wixom, one is an early article (2002 I think) that describes then an LS6.

 

Hi AZ-vette, what ever happened with your balancer? Did you add weights? The inner and outer hubs of my balancer slipped, as well? So no real way of knowing what the original setup was relative to the crank. I have had my local dealership order weights. How did you handle yours? Any problems?

 

Obviously I am way late responding to do you any good, but figured I would for anybody else that reads the post.
I didn't add any weights since I wouldn't know where to put them. I've had no issues since, and it's been several years since I did the work. I did get the part number for the weights from GMPartsHouse.com. They are;
3890192 = .50 long
3890193 = .75 long

 

Thanks for the response AZ-vette. A late response is better than none.

I did add weights to mine and have not had any harmonic balancer issues since.

 

great info thanks.