I agree with anderkart, smoke only on start up is usually valve stem seals or possibly the valve guide itself, if it was bad rings they typically smoke all the time not just at start up. When the engine sits with a bad valve stem seal it allows the oil that pools up by the valve stem to wick past the seal and build up in the cylinder causing a some smoke at start up. Do a compression test or better yet a leak down test and it can tell you what is going on if you have bad compression, or a burnt valve, and if you pass that and nothing is leaking air then it is just valve stem seals.