It could very well be the rockers or cams, and it depends on whether you or your mechanic are willing to do what is necessary. If the engine had regular oil changes (faithfully every 3,000 mi) then the top end of the engine should be pretty clean. The problem is that carbon accumulates around the rockers and gets into the cam and rocker lobes, causing rapid wear. Frequent oil changes reduce this, but don't completely prevent it. The main thing is, if you like the car, negotiate the price knowing you might have some cam work to do (should help drop the price quite a bit). When you have the car, immediately remove the valve covers and carefully inspect all the lobe surfaces, rotating the engine. Use a small mirror to see everything - it is easy to miss rocker surfaces which are beginning to wear through. If the cam lobes are not badly damaged they can be polished up in situ. Rockers go bad first, then damage the cam lobes; replace with new or good used rockers and you often don't have to replace the camshaft. I've done it all, and you can too if you are willing to buy or make your own cam gear holder, etc. I maintained one 76 B27 and one 80 B28 this way. The '80 was a super car. Everyone complains about the V6, and even the B280 doesn't get the mileage one would wish, but the B28 and B280 have plenty of torque - good for climbing long hills on the interstate - and are also plenty smooth. Just a different personality than the turbo B23, and a greater cost if there are cooling problems, so you will want to keep good, fresh coolant and a sound cooling system, since most Volvo mechanics don't want to replace head gaskets on these engines (although they will often buy these cars themselves and do the job....) The bottom end of these engines hardly ever shows any wear, but the timing chain can break and lock up the engine - another reason for frequent oil changes.