Crank balancing 27, stock crank , light bobweights.

I've recast the bobweights several times, got them down to 91mm diameter and full width and 718g with a spread of only 1g for each of the halves. 714g is the correct weight but this will do for now.
It's a completely stock 6G72 crank, the bobweights have been calculated for those cheap china lightweight conrods and forged pistons. Those rods are about 100g lighter than the stock rods so about 600g difference in total. When you see it shaking around, that's what your engine is doing internally when you either didn't balance it or you balanced it wrongly using the wrong balance factor. It's spinning at about 900 rpm. It's hard to see on the vid but each end is oscillating by about a half a mm.

[@ChiefCabioch]

This is someones idea of a bad joke...

[@1magnit]

That's what happens when you fit aftermarket rods and don't balance it.

[@ChiefCabioch]

@1magnit every Aftermarket rod, steel or Aluminum I've balanced cranks with were withing 2grams, if you think 2 grams makes a difference the how do you compensate for oil under the piston on the up stroke, verses oil under the piston on the down stroke, there are simply to many variables to try for perfection, cause it can never be obtained, I've run a Stewart Warner model 2000 engine balancer since the mid 70s, and had customer's from Oklahoma, Kansas, Arkansas, Louisiana, Texas and New Mexico, I was running 3% over balance long before most even knew what it did, don't over think the balancing, if it's jumping up and down on the machine, you aren't done yet, but spinning one 6000rpm isn't going to give good results, that's why S&W uses around 440rpm, when you spin it faster it will smooth out, but slow it will hop all over the place...

[@1magnit]

@@ChiefCabioch We're talking about dynamic balance, it's a 60 degree V6. There's about a 100g difference in weight between a stock rod and a cheap china rod.

[@ChiefCabioch]

@1magnit new rods lighter? Or heavier?. If heavier your going to be putting in some heavy metal plugs, but I'm talking about the machine he's using, I don't see that machine is accurate and you have 2 planes of balance, static and dynamic and you need to lock one side while floating the other, I've been balancing engines for 50 years, not much you are going to discuss I haven't dealt with,

[@ChiefCabioch]

@1magnit so it begs the question why are you using Chinese rods?