con rod placement

[maldotcom2]

So i've got my 6 conrod and piston assemblies on the table but i cant remember whether i marked them in firing order, or front to back.

I'm replacing the pistons and all bearings, so does it matter the placement of the conrods themselves? I'm assuming they're identical.

[Blown V6 Hatch]

If the rotating assembly has been balanced then it won't matter where they go.

[maldotcom2]

Well i've never had it balanced, i dont know if they're balanced from the factory or not.

[Blown V6 Hatch]

You put new pistons on without having it balanced? Hello vibrations....

[maldotcom2]

Well i havent done it yet, im about to start putting it together. Looks like i'll have to get it balanced. Thanks for the heads up on that, rough cost?

[Blown V6 Hatch]

About $250-$300 i think, depending where you go.

[maldotcom2]

Alright, well that's not disasterous. So i'm not real familiar with how they do it. Do I give them just the crank and pistons or the whole assembled bottom end? Cheers.

[Blown V6 Hatch]

You will need to give them the crank, rods, pistons & rings, big end bearings, harmonic balancer & flexplate/flywheel. They will balance the whole rotating assembly for you.

[maldotcom2]

Ok sweet thanks. I've done some research and from what i understand they balance the crank on a machine and the conrods are balanced separately by weighing each end and making them all weigh the same by removing material.

Would I be justified in saying i could get the crank balanced, and then balance the rods and pistons myself?

Having said this though, the ecotec is an internally balanced engine and the crank should already be balanced and changing the pistons shouldnt affect anything. Assuming of course the flywheel is balanced on its own.

[Blown V6 Hatch]

It shouldn't affect anything if the pistons are the same weight as the standard ones, but generally aftermarket pistons are a different weight....That's where the problem lies. You probably could do the rods & pistons yourself i guess, however for the sake of $250odd, i'd just send it all in and get it all done professionally.

For an engine like the Holden V6 that is inherently harsh, it's definately worth getting it balanced IMO...

[maldotcom2]

I weighed the new pistons and they vary by 5 grams between each other. Is this unusual for brand new race pistons? As it turns out the new pistons weigh the same as the old ones give or take a couple of grams.

[Blown V6 Hatch]

Yes, New pistons will vary. Hence why you get the rotating assembly balanced. A few grams will cause a massive vibration....