I just received my new KB 96mm 2.0 pistons and 2.0 "H" beam rods. I was going to send all of my rotating components out to be dynamically ballanced because I thought it was the right thing to do.

I weighed all of my rods on a scale acurrate to .0001 Kg and they are all the exact same weight. Same with my pistons.

So here is the dumb question if they are all the same they why ballance them? I think that I will just ballance the crank, flywheel, clutch and fan.

Am I missing something here?

Thanks

David

So here is the dumb question if they are all the same they why ballance them? I think that I will just ballance the crank, flywheel, clutch and fan.

Am I missing something here?

Thanks

David
[/quote]

Nope, you're not missing anything.
On our horizontally opposed engines, the rods and pistons perfectly counterbalance each other, so they're not included when balancing the rotating assembly. On a 'V' engine the shop does make up "bob weights" to simulate the pistons & rods since the crank is not 180 degrees opposed....

Wow. Where did you get them from? Was balancing part of the price?

Dynamic balance is more then just pistons and rods. Its everything that spins. Crank, flywheel, clutch, ect.

Still a good idea, since you ARE building a performance engine.

Zach

Bad info...

Pistons and rods DO need to be balanced.

Does not matter if its a T1 or a T4, they absolutely need to be balanced.

On a stock T4, the max difference between lightest and heaviest rod is 6 grams, and max weight difference between lightest and heaviest piston is 10 grams. (page 11 of your haynes manual).

This is the MAX allowable difference. In practice you want to have the rod/piston combo to be balanced to within 5 grams from the lightest to the heaviest (the weight of a penny). If you plan on spinning the engine up, you want the total difference to be as small as possible. The built combo includes the pin and bearings.

Zach

He said that they're already perfectly balanced.....I meant that they aren't included in the dynamic balancing step if they're already perfectly balanced.....

I have access to a nice scale that is acurate to .0001 KG

All four KB pistons & pins measured .500 KG
All four 2.0L "H" beam rods measured .525 KG

I'm asking the questions because I don't know

Thanks

DAvid

The rods need to be balanced end for end, not just total weight.

The Cap'n

,Yep, what he said.....do a youtube search on connecting rod balancing....you do need to send the rods to the shop.

curious how you balance (end to end) an forged H beam rod?

like this http://www.youtube.com/watch?v=QLpiF0E0EJU

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