LOL... well, all reports are that the factory balance range was not all that great... reportedly a range of + or - 25 to 30 grams. And the KB weight change in the 360 is a lot less of a change than for the 340 or 318; the stock 360 pistons were quite a bit lighter already than the others. Stock 360 bobweight is right around 2150 grams.... with the KB flat tops and stock rods, it changes to around 2078 grams.
The weight difference is not going to be all that big, but the compression change WILL be a big change. Those old stock pistons are sooo far down in the hole LOL
