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Balancing the rotating assembly

I saw that the other day when I was looking for information on it. I didn't understand the lengthy process beforehand. I imagined it was a dynamic process.

One of the main parts of our machines at work are static balanced, but when we test, if they're out of spec. then we dynamically balance. It's a much different animal, though, and can weigh many tons.
 
Not exactly. I mentioned NOT letting them remove weight from either the flywheel or harmonic balancer. MAKE THEM remove it all from the crankshaft.
At about the 17 minute mark of video he mentioned the flywheel weight and what if they changed their mind later to go from stick shift to automatic.
There is also what if the flywheel (or if automatic the flex plate) needs replacing because of teeth or other reasons.

Then same issue about the harmonic balancer. I have a drilled balancer where a shop drilled it. Then later when it needs replaced you are hosed. So when I saw it, i made them redo the crankshaft with me watching because they didn’t follow instructions.

Also when you want to use a fluidampr- they can not balance with it. So they use a factory balancer to do the work. Later when you add a fluidampr it helps even more.
Because remember the part they mentioned the resonance frequency, and the amount of oil? The balance still gets slightly off so the fluid in the balancer now is working to offset those two minor issues rather than the massive weight of different pistons or rod weights that are always off.


For those that have ever replaced a factory balancer with a fluidampr- they feel the difference. The shake is less. Well doing it this way is a bigger difference. Then adding the fluid damper is added to the improvement all the way from idle to peak rpm —for this engine anyways. Our peak rpm is low so it isn’t as much as an engine that hits 8,000 rpm. But because ours is low rpm by design, GM & GEP allow for more weight out of balance to save in manufacturing costs. Then our crazy high compression adds into it as well.

Anyone that ever gets a 6.2/6.5 balanced and talks to the machinist afterwards- they always comment how ‘bad’ it was. This includes p400, scat crank, etc. taking it to a machine shop that frequently does diesels- far more common now than used to be- they will have a higher price for diesels because they learned the hard way.

If any cares to see it, I will try digging up the drilled balancer I have. It could still be used on a stock engine but obviously will be slightly different than stock. I kept it because so many guys around here just don’t know the bad balancer Rubber issue, and this would be better than nothing for them. But from my experience, these engines are always so far out and generally the same half of the crank is always heavy. I think it was simply an engineering error made that GM just never corrected and GEP followed suit. Even the scat cranks are heavy to that side. I had the machinist I normally use and 2 that I onmy used once each compare and all the cranks were heavy on that counterweight- so just a factory spec is off. Again- larger tolerance error allowed because it is a slow revving and low rpm engine by design.

A guy was asking me a while back to describe why this is important to do. My niece was hanging in my leg as we were speaking and the example was perfect.

Time yourself running 40 yard dash. And think about how tired your legs are at the end of a work day. Now, duct tape a 2 liter of soda to one of your ankles....
Lightbulbs come on mighty quickly as to speed, mpg, longer life of the engine even if used as a put-put truck.
 
Seeing in the video what the machinist has to go through to balance the assembly, I'm sure it takes several hours for this process. I am curious though what the average cost to a customer is for this service nowadays.
 
I had my shop add weight where needed and they did, also they balanced the pressure plate separately so if ever needed to change it out all that would be needed would be bring in the plate for them to balance... there is a lot to getting everything right. They balanced mine to race specs even tho it is a low rpm motor... Everything that bolts to the crank is needed to do a good balance, down to the front pulley ....
 
Around $350 here.
EWC said:
It took 4 slugs of heavy metal to get mine right . Don't think you need a Fluidamper if the balance is tight . I just used a new GM piece .
Click to expand...
You don’t NEED a fluidampr. Also don’t meed to balance it any better.
But the more balanced it is, the better. Now take a perfectly balanced assemb, and measure it at different rpm’s. It will become slightly out of balance at specific speeds - there is a resonance to it.
Now add oil. At different rpm, different amounts of oil will stick to the pistons, rods. That will throw off the balance.
This is where the fluidampr adds up to helping even a ‘balanced’ engine.

Some people go another step- balance camshaft, timing gear system, etc.
Then there is a transmission- ESPECIALLY manual transmissions gain from having that balanced. Trans is far less than the engine in gains, but helps. There is always room for improvement- the cost and diminished returns is the question.

Internal balance has more impact than external. So I always push for do the inside of the engine when it is apart. If not apart then the fluidampr is best money spent.
 
There is plenty of arguments in whats best in engines- low rpm high torque vs low torque high rpm and hp that kicks in above 5,000 rpm.

One of the arguments is wether to drill and grind away extra weight vs adding it.
Chris chooses the more expensive option of adding weight. This is definitely the way to go for his application. He wants to have sustained power while driving down the hiway. When he is doing 50 mph and steps into the throttle, the added weight already in motion will help him accelerate easier. Think 240 lbs running back on 3rd and 2. That weight helps carry him through the load.

My application is different- I want faster acceleration from 1,000 rpm up to 2,500 rpm. I want to leave a stoplight quicker- or have faster acceleration to get my 37” tires spinning from a dead stop up onto boulders, or out of sand. So a lighter weight getting spun up faster in less time helps me more.

The fluidampr helps Chris more than me for the heavy trailer he will tow- sustained energy. Remember: rotating flywheel— aka heavy flywheel in motion- is still the best stored energy we have known to mankind. But like a battery you have to charge in that energy.

So things like titanium rods would help me more than Chris. N8in8or trying to go fas as possible- he would benifit even more from it. Possibly to the point of the fluidampr actually is too heavy because of the lost energy in spinning up the heavy balancer.

A lot of people have to experiment themselves to see the differences and what is best for them.
But things that are universally good- balanced vs not- is always a smart move.


And something I remind 6.5ers of- on e you understand how balanced assembly helps- don’t do this and undo it by having unbalanced injectors. If cylinder 1 gets 10% more fuel than cylinder 2, think how bad that throws it all off every revolution. Now if all 8 are different...
 
Because the fluidampr adjusts so much- you have to do the Balance job with a factory balancer.

A way to think of it is using balance masters on a wheel. It is best to balance the rim by itself, then with the tire on it. Later when the tire picks up rocks/mud and also when the rubber wears away- the balance master will help make up for any inconsistencies.
 
Unbalanced injectors are injectors that don't produce the same amount of fuel as the other injectors . All need to have the same " shot " when it's their turn at combustion to have a smooth running engine .
 
Will L. said:
There is plenty of arguments in whats best in engines- low rpm high torque vs low torque high rpm and hp that kicks in above 5,000 rpm.

One of the arguments is wether to drill and grind away extra weight vs adding it.
Chris chooses the more expensive option of adding weight. This is definitely the way to go for his application. He wants to have sustained power while driving down the hiway. When he is doing 50 mph and steps into the throttle, the added weight already in motion will help him accelerate easier. Think 240 lbs running back on 3rd and 2. That weight helps carry him through the load.

My application is different- I want faster acceleration from 1,000 rpm up to 2,500 rpm. I want to leave a stoplight quicker- or have faster acceleration to get my 37” tires spinning from a dead stop up onto boulders, or out of sand. So a lighter weight getting spun up faster in less time helps me more.

The fluidampr helps Chris more than me for the heavy trailer he will tow- sustained energy. Remember: rotating flywheel— aka heavy flywheel in motion- is still the best stored energy we have known to mankind. But like a battery you have to charge in that energy.

So things like titanium rods would help me more than Chris. N8in8or trying to go fas as possible- he would benifit even more from it. Possibly to the point of the fluidampr actually is too heavy because of the lost energy in spinning up the heavy balancer.

A lot of people have to experiment themselves to see the differences and what is best for them.
But things that are universally good- balanced vs not- is always a smart move.


And something I remind 6.5ers of- on e you understand how balanced assembly helps- don’t do this and undo it by having unbalanced injectors. If cylinder 1 gets 10% more fuel than cylinder 2, think how bad that throws it all off every revolution. Now if all 8 are different...
Click to expand...
I noticed the benefits of balanced injectors on stock engines - or. At the very least, imagined I did.
 
jrsavoie said:
I noticed the benefits of balanced injectors on stock engines - or. At the very least, imagined I did.
Click to expand...
If you go from ones that are out by 10% or more to balanced ones- even if they are all new - it is very noticeable.

So back the the rotating assembly...
There is things some people like to do for higher revving engines like dressing the hard edges of the rods. Being so low and rpm, it won’t help us much but I wouldn’t say don’t do it to a guy if he believes in it. But definitely do this before getting them balanced

Also something not mentioned is wrist pin bushings. If dealing with brand new engine great. If a rebuild- don’t forget to replace them (small end of the rod. If you don’t know how, the machinist can pop them in for a few bucks while he has them. Many people leave the bushing oil inlet port stock. I always enlarge mine to the opening of the rod hole. Remember the way oil gets into the wrist pin is the top of the rod snd since you are removing material to do this- it must be done before balancing.
 
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