Somewhat relieved to see a current thread on this topic....as the title hints, I've got an '84 300SD w/ 280k miles on it and put it into a local mechanic for an oil change and a valve adjustment. However, the diagnosis from the mechanic is that I've got significant valve guide slop on #2 cylinder intake valve (like 1/4"!). So, it sounds like the only way forward is to consider a head replacement. I found Metric Motors and the link to a completely reconditioned head - and glad to know they are reputable. However, my mechanic said that just replacing the head doesn't mean all will be will - these engines wear as a completely integrated unit and suddenly putting a perfectly sealed head back on could create blow-by issues further down the road. At present the engine has been getting a solid 25MPG for almost three years, does not burn oil and has been running very well otherwise. I have access to a spare engine which has a head with approx 180K mi on it which I could get for free - but not sure if there's any hope of fitting an as-is head either....anyone got any suggestions? I've invested lots of time (and money) and this beast already - but love the car and am tempted to keep it running. Just don't know what to at this point..thanks in advance for help/comments/insights/suggestions!