I was talking to a local engine machine shop about some work on my motor and brought up balancing the rotating assembly. I mentioned that I scribed my harmonic balancer before I pulled it but didn't mark it very well and was a little worried about putting it back on balanced and he said it didn't matter cause the harmonic balancer was a neutral component to the balance......

I'm using the shop manuals to guide me on all my work and they seem to disagree with him, anybody have better info on this, I'm not finding much to agree with him on the internet

 

It goes back anywhere. Just make sure to use a new bolt and properly torque it.

 

Like farmington says ... put it anywhere

The LS engine is internally balanced.

 

sounds good enough to me and not to doubt but if it can go anywhere then why does the shop manual make a deal out of making sure you line it back up?

 

Put a new Powerbond balancer on it and be done. There is nothing to line up. If you think you might add a supercharger one day, then pin it while you're there. Other than that, you're overthinking this.

 

The way I look at it is that this is standard practice for disassembly of an engine to repair an issue. The intention is to put everything back as it came apart in order not to create potential balancing issues that where not present prior to the repair... the dealership does not want to waste time chasing ghost and gremlins after making a repair for something else. so it’s just a good practice... however I would not lose sleep over not doing it...

although yea it’s a zero balanced rotating assembly, it’s still common practice to balance that rotating assembly with the factory balancer installed. Since the factory balancers are tolerance built, there will always be some measurable amount of out of balance... it’s just typically not enough to overcome the function of the balancers job to absorb that small amount of out of tolerance.

this is why when building engines and plan to use an aftermarket balancer such as an ATI Superdamper, I will have the rotating assembly balanced with the factory balancer and install the ATI during the build. This is because the ATI works so well that it will absorb to much from the crank and actually throw off the balancing.

SPEED SAFE, NICK

 

This was a good reply, thanks for it, but I don't think I got what you were trying to say on that last sentence......?

 

When balancing a rotating assembly you want the balancing to be as accurate as possible.

The problem with using an ATI Superdamper during the balancing process is that the ATI will literally absorb and remove most of the harmonics/vibrations and hide some of the imbalance from being detected. Your factory balancer is not as effective at removing harmonics and the imbalances will be easier to detect. Which in turn will give you a much better balanced crank... once completed, adding the ATI after the balancing leaves less harmonics for the ATI to remove..

Does that make any sense? If not I’ll try to reword it...

SPEED SAFE, NICK

 

Since LS engines are internally balanced, do you really need the harmonic damper (proper name; it's not a balancer) on the crank while balancing?

 

Well hell no! If you clock it different the next time you install it vs the first time, it's just that....different. No better, no worse, just different.

 

The shop manual describes marking the pulley position and transferring balance weights ("if applicable"). If you don't have any weights installed, it shouldn't be applicable.

ATI has this to say on the subject:

 

ok yeah, that makes since, I think I was just not grammatically comprehending, thanks for the clarification.

 

The factory fine tunes the engine (Corvette and others) by putting small weights in pre drilled holes in the balancer. I witnessed this during a factory tour. Usually it's impossible to determine what the weight is without drilling it out and it's in a blind hole. These weights are available at the GM parts counter (Special order).
OEM balancer weight "short", 0.5" P/N 3890192
OEM balancer weight "medium", 0.75" P/N 3890193
OEM balancer "long" weight is not available - use two shorts

Typically if you are getting a rotating assembly balanced the engine builder will balance the crank with the flywheel and balancer as a unit.

 

This was discussed several weeks ago on here. There is a guy in Alaska on this forum who would love to argue with anyone about this. He would rather replace a known problem balancer with the same known problem balancer. I am reasonably sure that when he reads this he will chime in.

 

I'm not going to argue with anybody about this. I was convinced that balancers were zero balanced on a factory built LS engine until I saw an engine at the end of a GM assembly line fired up on natural gas and weights placed in the balancer. I asked about this and was told it was a fine tune balance they do on some engines. This was a Corvette engine. I would think aftermarket balancers would be zero balanced for internally balanced engines.


Here’s an example of where the factory harmonic damper balance weights mentioned in the main text might go. Just so we’re all on the same page, balancing does not negate the need for a functional harmonic damper! Dampers absorb energy from crankshaft torsional vibrations (most significantly, from the firing of each cylinder), limiting distortion of the crank. These forces exist independently of the forces that would be created by an unbalanced rotating assembly—you still need a good damper, no matter how good your balance is!

https://www.lsenginediy.com/ls-engin...ne-shop-guide/

 

All I hope to do if I need to replace my damper is maintain the factory balance. GM powertrain engineers thought it important enough to balance each engine using weights in the damper. The aftermarket does not have provisions to relocate my weights in the same location.

 

For what it's worth I have replaced a few balancers with the Powerbond AND OE balancers without adding the weights in the factory positions with no hint of a vibration afterwards. Obviously there would be an imbalance but not detectable to me. I found that it was very difficult to remove the weights from the original balancer to see what length (weight) they were so I could order the right ones and re install them in the new balancer. The way it was explained to me at the engine plant was engines destined for the Corvette and higher cost vehicles (his words) got the extra HB balance weights where vans and trucks did not. I won't say it's impossible but removing weights from the original balancer would be difficult because they're installed in a blind hole so you have to drill them out from the back and punch them out to see what they were so you could replace them, then you'd have to install the balancer back exactly in the same position as the original. In situations where the balancer has moved on the crank (some do) or if the outer ring has shifted (one of the main reason we replace them) you wouldn't be sure you were putting everything back where it should go. I guess if you're really fussy you could do this but would it be worth it?

 

Assuming you are putting on an aftermarket balancer, or already have one, have the machine shop do the dowel that’s used to pin the balancer THEN get it balanced. It can only go together in one position then.

 

Think you just measure from the damper face to weight. Holes are all the same depth weights are three different lengths. Simple lightest weight will set deepest with heaviest being flush the face. Will it make a difference I have no idea. GM think it does. Van and truck engines not spin up like my 6 speed LS3.

 

????