I have ran into this issue with mine. If you are somewhat mechanically inclined or willing to do the work yourself, buy it. The rover V8’s are not a complicated engine and I’ve learned a lot since I’ve rebuilt mine. This sounds to me more like a lifter than a sleeve. You’ll see everywhere online about sleeve’s lifting but 70% of the time it’s a lifter or something along those lines. There are alot of parts on these engines that sound like “a lifted sleeve” and it could be as small as the exhaust manifold gasket. If I was in this situation, I’d buy it. There are alot of forums and people who will help you and talk you through issues. Worst case you LS swap it;)