Darrel,
Drivability issues are difficult to diagnose even when the car is presented in the shop. From a distance we can only rely upon your description, so please be very precise with each statement; indicating exactly what is being adjusted and what results. I'm not sure what is meant, for example, by the phrase," No change, It also pops and backfires occaisionally foot off the accellerator - under compression." Does it backfire through the carburetter? or the tailpipe? are you at speed and decellerating when this happens? What is meant by "under compression"? Any running engine is "under compression.
You mention that the engine is "hunting". Now, I'm sure it's not hunting for rabbits, but I need to know if you mean the engine speed is surging up and down, or just is almost dying and then recovering. "turning the adjustment does absolutely nothing." Which adjustment?..and so on.
Darrel, sometimes when I don't get back to someone right away it's because I'm considering what has gone before. I also have a very busy shop to run. I'm sure you can appreciate that. Also, sometimes these threads can "go dead" because the folks reading them cannot understand what is being said and don't or won't take the time to try to interpret. We each have our own internal language to describe what's happening and often others are not on the same wave length. I have not forgotten you, but it must be up to YOU to keep the thread going, as everyone has plenty of other concerns in this day and age. Sorry, didn't mean to lecture.
Bluish smoke is the burning of oil. Excessive fueling causes black smoke. Look very carefully at that smoke color. Look for vacuum leaks at the juncture of the carburetter and the manifold, and where the manifold joins the cylinder head. Also look ANYWHERE downstream of the carburetter where ther is any opportunity for leakage, such as at hose fittings or plugs. You can diagnose these things by spraying (CAREFULLY & SPARINGLY) carberetter cleaner at the suspected points with the engine running. If the engine speed changes coincidentally with the spraying, you may have found a vacuum leak.
My latest speculation is that you could have a head gasket going bad. The sudden appearance of oil smoke, along with the uneven running causes this thought. BUT, don't assume this to be the case and rip it's head off! Always diganose to a virtual certainty first, THEN act. Let me know what you are finding. Cheers.
Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon