I want to switch out the stock chevy 5.7 rods on my 383 with some eagle ones that weigh ~650grams.
The assembly was spin balanced last year and I am hoping to avoid rebalancing it? Is that weight close enough to stock or would be with maybe a little grinding to avoid rebalancing?

 

Not worth trying.

You're spending $350 on a set of rods, a couple more Bens on tear-down and build-up, however much time and effort in your labor, and you're going to save.... what.... $75 on balancing??? Bad idea. Baa-aa-aa-aa-dddd.

 

try $260 on balancing

 

worth every penny

The absolute only way I would even try it is if I had the balance card from the previous build, and a scale of adequate precision, and I could duplicate the old big-end and small-end weights exactly. It's the wrong place to try to save pennies... kind of like valve springs or rod bolts.