John,
Check that 1:  There is a hole in number 2 cam bearing to each of the lifter banks and also to the oil feed gallery below. 
                  2:  That there is a groove in the cam to allow oil feed to each lifter well.
                  3:  Turn the oil pump clockwise with a drill.  With cam out, oil should enter number 2 cam bearing area.  If not problem below.  If it does install cam, and rotate cam slowly by hand, oil should enter each lifter bank one at a time depending on groove in cam location.  If not recheck 1 and advise.
 
John

SOLVED!!!!!!!!!!!
 
OK after pulling out the cam there is no oil groove in the journal.  I recall buying a few Essex engines from South Aftrican Sierra V6's I pulled apart, they ran shaft mounted rockers so ne need for the groove.  I guess I gave Clive one of those to re-grind.  Now to see if he can do the groove or whether I get another cam....

You failed to mention at the outset that the cam had been changed. It just goes to show that when rebuilding an engine one can never be too carefull, especialy if mixing and matching parts. Its a good lesson for all of us. Im glad its sorted without tears.
This would make a great subject for a technical article in the club magazine.

Just saw this at 10pm Sun night ! ............................still wondering why one bank got oil and not the other bank since wrong cam with NO oil groove was fitted ?  
 
Glad you got to it before any massive implosion/explosion  

............at least you didn't lose your cool and throw a brick at the windscreen like my moron cousin did when he
lost his cool with his Torana while trying to fix it himself at his home !  .......being laminated you can guess what happened next.......yep.......brick bounced onto the bonnet wrecking the new paint as well as dinting the bonnet............what a loser.......... All because he put the dizzy back in 180 deg out !