@ how many miles should a timing chain be changed....?????

There is no miles to change replace as needed 100000 good time to check if quite why fix what's not broken Start to get noisy replace system tensioner gears chain all Seals also replace waterpump.flush system My thoughts there there why pay twice same job cheaper now neg with job.cheaper now.check belts and hoses also thermostats also. Ace

Also if you indeed do have a timing chain, you don't need to change it. The are good for the life of the car. Let me know if this helps. Regards, John

Follow the owner's manual for the recommended maintenance intervals, do not listen to people on here who are just guessing. Timing chains generally do not need replacement unless they fail but timing belts always have a recommended replacement schedule. If you do not have the manual, look it up online. It will give you some idea of the maintenance that is coming due. (Of course you have no idea what was done previously on schedule unless the seller has receipts.)

Most of us on here are not professionals in the automotive field. We are here to help. Generally a timing chain is good for the life of the engine. Yes, I ALWAYS recommend reading the least read book book in the world. Yes, the owners manual. We go by the facts we are presented with on the post and our knowledge. If we are responding to a question, it usually because we have some idea of what we are talking about. Sure, the engine could have taken a side hit, the chain could have fallen off at some point, but we don't know that. We answer based on the questions add they are written and posed. We're not mind readers.

I have found that timing chains stretch substantially, changing valve timing and need replacement at about 100K. Tensioners and guides should also be replaced at that time. While the chain may not break for another 50k miles, the car will run much better when it is replaced. Life of the engine is sometimes stated for chains but is not correct.

John, you are right, the timing chain for any vehicle they are replaceable, its good for a lifetime for the engine. Timing belt they do recommend to change but not timing chain.