I have been searching through old posts for information about many subjects. This is my first post. I’m sure there will be many others. I hope Jag-Lovers will be able to help me bring my old Jag to life.
Can the big end and/or crank bushings be changed without removing the crank?
Both can yes. All the main caps would need to be loosened though so the front of the crank hangs down a hair and is supported by the chain. This will create enough of a gap to poke the upper shell out and around. The much trickier bit is trying to polish the journal and clean up the residue before installing new bearings.
Welcome by the way 
+1. Done it myself…
I have not removed the caps yet but the engine has no rust in it. Why would i need to polish the journals if they look good? The cam journals still look good.
Polishing the journals is just good engineering practice but if they look good then it’s over to you whether you polish or leave as is.
There could easily be some contamination on them scraped from the old bearings, especially if any debris got in.
That’s the other caveat. If the engine’s in the car then you have to set up a clean area so no dust gets kicked up.
Replacing the bearings without cleaning out the crankshaft sludge traps might not be economic in the long run…
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Yeah, I was thinking that too, Bill. I’ve done it twice only and the volume of crud extracted was remarkable. It can be a bear of a job with the crank on the bench, I can’t imagine the difficulty doing it in situ, though I suppose it can be done.
Do you have a good reason to do so? Have you plasi-gauged them and found them to be loose, or are they a real mess?
I think once you’ve removed the bearing caps and lost the crush you’re pretty much committed, no?
I’ll let someone smarter than me to answer this for real, but I don’t know if it isn’t necessarily taboo to re-install shells if they look good and gauge correctly.
Cam journals and bearing shells take low impact loading. Oftentimes will go without attention for a hundred thousand miles or more. They will not be representative of wear in the bottom end.
Perhaps, though XK main and big end shells are pretty cheap in comparison to many other engines so to my mind it would be false economy not to replace them.
It is well worth remembering that replacing main bearings was a standard job on engines in days (long?) past, with the engine and crank in place.
With engine out, cleaning the crank of its crud certainly makes a great deal of sense.
I replaced the main and rod bearings in my coupe last summer while the engine was in the car. Reward was greatly improved oil pressure. Only needed to polish center journal - used fine emery cloth soaked in clean oil. Put grease in the oil hole in the crank to catch crud and carefully cleaned it out after I finished. What was in the grease traps stayed in the grease traps.
I posted topic here: Missing the bullet, or minor flesh wound only
Thanks for the quick response everyone. I can now see that it would be possible to change the bushings with the crank in.
I have found that my oil pump ate a split pin and for some reason the filter didn’t catch it. The felt washer in the filter was mossing. Now I have removed the head and crank. I plan to bore the cylinders, change all the bushings, clean all the pasages and try to tind and fix all the PO’s mistakes.
Nothing has been ground or bored in this car so I am thinking about going with the original 9:1 CR as the head and engine indicate, and using a fat head gasket to reduce the chance of preignition. I hope I won’t have to resort to retarding the timing. The gas in Arizona is pretty low quality.