I recently acquired a chevy 350 manufactured in 2015 for free because of some crank issues. I'm in the process of rebuilding it and have finished the disassembly of the engine. The engine itself only has 200 miles on it would it be necessary to replace the piston rings on the piston heads or can I leave the ones in there? Would that cause any loss of compression?
With only 200 miles on the engine, I'm thinking you could get away with using the same rings on the engine as long as you didn't see any scoring on the cylinder walls or any other obvious damage.
With that said, a stock set of piston rings is dirt cheap for a 350 or a SBC in general ... as long as you are talking about the Gen I SBC and not a Gen III SBC (LS1)(I know, those aren't exactly 350ci (only 346ci), but yah, throwing it out there). You can get an entire rebuild set, to include bearings, rings, and gaskets for under $100 from Summit (at least at the time of this post). With only 200 miles on the block, I'd bet you wouldn't even have to bust the glaze on the cylinder walls as it should probably still have a great hone.
You have to buy the gasket set anyway and everything is all opened up to you already, it really doesn't make sense not to put all fresh parts in there. One and done ... do it right the first time and you won't have to worry about it anymore.
I would replace the piston rings and inspect the pistons for any signs of damage. You are already investing money in repairing the engine. It does not make sense to skip such an important part. Make sure that the cylinder surface is prepared properly. A good machine shop should be able to do the work for not a lot of money.
Note: If you comment about the "crank issues" we could probably help identify other potential issues that you may not be aware of.
If you are going to remove the pistons anyway, in order to fix the crank issue? Sure why not, because you are going to have to put rings in it when you reassemble. But, if they were replaced when it was rebuilt 200 miles ago, and they were installed correctly? There's really no point.
Are you sure the previous owner installed/honed the cylinders properly?
If you have any doubts as to workmanship previous?
I think it's a no-brainer to ensure that the whole engine is rebuilt properly.