Balancing

[87Gnastey]

So what's the going rate to have a rotating assembly balanced? ('87 GN)

 

[charlief1]

That a really broad question. It depends on what you have and how you want to balance it.

 

[87Gnastey]

I have Diamond Pistons, Eagle 4340 crank, Eagle 4340 rods, BHJ Balancer, and a J&W Flexplate.

 

[charlief1]

I have Diamond Pistons, Eagle 4340 crank, Eagle 4340 rods, BHJ Balancer, and a J&W Flexplate.

So you're wanting a standard balance at what % of weight? Stock is 33.3% and you can go as high as 50%. Where are you located will also effect the cost.

 

[87Gnastey]

NM got a price

 

[charlief1]

Check with GNEric and dr_frankenstien. They're in NM and will know the best service as well as price.

 

[turbodave231]

Call Dan at DLS and compare his rates. You might pay a little more for shipping, but you'll get it back exactly right and he is reasonable.

Dave

 

[87Gnastey]

Haha no I live in MA, I meant nevermind (I had a price), but just out of curiousity why would the % of weight balanced affect the cost?

I have an idea, but this is my first motor so what do you mean by % of weight?

FYI. My machinist quoted me at $250-$300.

 

[charlief1]

The percent of rotating weight is what it's balanced with. It won't effect the cost but it can effect the way the engine vibrates in the chasis. 33.3% is what the factory did to cut down on vibration transfered to the chasis. Using a 50% will give the best for the engine but felt vibration will be higher.

 

[87Gnastey]

Makes sense, but what are you measuring? (33.3% or 50% of what?)

 

[charlief1]

Makes sense, but what are you measuring? (33.3% or 50% of what?)

The mass is the weight of the rods, pistons, rings, and bearings. They have to measure them and equalize them. Then they take the percentage for the weight of each rod ect and it's attached to the where the rods mount.

Like I said, the factory used 33.3% of the weight of the rods ect to balance and it will cut down one plane of vibration but if you use the 50% it will allow the engine to live better, but you will feel more chasis vibration.

 

[87Gnastey]

Thanks!

 

[turbodave231]

Balancing costs more when you have to add mallory metal to the crankshaft. When you balance at a 50% balance factor, you typically end up using heavy metal in the crankshaft which will cost you more $.

Honestly, I've done both 50% and 36.6% balance factor on these engines. It is hard to tell the difference. You will probably end up cheaper if you do 36.6% and I don't see any downsides.

Dave

 

[87Gnastey]

Ya I heard mallory isn't cheap. What are you at now for a %?

 

[charlief1]

You're right Dave, I goofed. The factory did a 36.6% not a 33.3%. I brain farted, sorry. Since you have a neutral balance crank you may not have to add metal but check with the machine shop you are using to make sure.

 

[ronbuick]

the builder I use does them at 50%, this is is 3rd motor that he has done for me, diamond pistons@ .020, manley valves, and a 210-205 club cam I had laying around, new of course,flat tappet, crank at .010, 100lb. springs, ported intake and heads, by a porter from Cali. who does not want to be known, scary is it not, this man has done this all his life,he moved to Boise from Cali. and just doing a few machine shops to bring in a little income, he has all the tools,bench, etc and will be supplied with the results of the flow on the heads and stuff, I will be picking up this hot bullet on Monday, will install this winter, my original motor has 118K miles and 500 or so passes down the 1/4 mile, so time for a fresh one, and she still runs strong, these are just amazing motors, just amazing at their capabilities and robustness.

Ron

 

[87Gnastey]

Amazing story

 

[Turbo6Smackdown]

How does a more balanced engine make more vibration...

 

[charlief1]

How does a more balanced engine make more vibration...

To put it in simple terms. Each engine design has an optomum angle between the cylinder banks. All engines work best at a 180 degree and will keep vibration down the best. A true inline will also have a good balance. When you go into a V design the the best angle to reduce felt vibration is calculated in terms of 3 angles of movement. Horozontal. Verticle. And I can't remember the last one but if you put two cones together at the smallest point and put that point in the center of the engine that's what it will look like. A v8 has the best angle for balance as a 90 degree between banks. A v6 has the best angle of 120 degrees between banks. When you reduce or increase this angle it will change the motion the engine creates while running.

For the Buick V6 at a 90 degree angle this means 2 of the plains of vibration/rotation will be increased and give you more felt vibration in the chasis. GM decided to balance the engins with a 36.6% rotating mass to reduce one plain but it increases the other. This is one reason the factory motor mount is kinda soft. It helps reduce the felt rocking sensation the engine naturally makes. If you do a 50% balance it will decrease the side to side motion and increase the other plain which will make the chasis vibrate in a different way and the motor mounts won't dampen the vibrations as well. I know it's a long explanation but it's not a simple answer. Sorry.

 

[Turbo6Smackdown]

I see. Don't worry about the length of your answers.. I wanna learn. Thank you for the explanation. So, since we're 90 degree engines, we can't fully realize a totally balanced engine then can we.