engine balancing

[345Dart]

In a balanced rotating assembly is there any advantage/disadvantage in having 150gms of extra weight at the rod journals verses having the same weight part of the piston?
I know - having it neither place is the best, however!

[amxauto-x]

If the weight is in the piston, it takes more energy to move the piston, and for the piston to change direction. That uses some of the horsepower.

[ohioDemon]

Amxauto-x has it down right. you wouldn't want the weight to be out at the end of the rod.
have you considered lightening the rod ??
has the engine already been balanced ?

[jelsr]

The further from crank centerline the more important the weight becomes. A stock rod/light piston setup will have a lighter bob weight than a light rod/stock piston setup.

[345Dart]

What I have is a set of polish, maged, shop peened Hemi style small block rods with 7/16" ht rod bolts - thus the rod end is much beefier than a stock 340hp rod to the tune of 150 gms more weight on the journal end than a CAT H beam rod and ±250gms more than a 340hp rod. The intended use is on a 3.79 billet steel stroker crank and likely a set of Diamond pistons. The total bob weight should be much the same as a stock piston with stock rods but in this case with the lighter piston should be better for quicker reving and durability/longivety.
Do you agree

[amxauto-x]

yes.

[b-1ken]

Light pistons are always beneficial due to the lower strain put on the rods at TDC after the exhaust stroke. I'm not convinced it takes any more HP to run heavy pistons though. Yes, it takes more effort to accelerate a heavy piston, but that torque is given back when the piston DEcelerates. Light balancing bob weights mean a lighter crankshaft, which will be easier to accelerate, but won't show up as constant rpm HP. The engine will also be more correctly balanced (less of a compromise)with light pistons.