hey brit, to put your mind at ease, I use valvoline VR1 Racing 20w 50 and get 6 bar when cold and 2 bar when hot, this is at idle, I get to 6 bar when hot when revs get above 2 or 3k.
Doing the oil pump is no problem, problems you might encounter are;
you might have to remove the exhaust manifold to get to all the bolts.
you might have to remove the distributor if you remove the shaft completely. this is because as you put the shaft back in it twists and the bottom of the distributor and the top of the oil pump shaft fit with a male and female connection.
If the distributor has to come off, they can be a PITA, I think you can get a large spanner on it underneath, you could try pushing and pulling on the spanner and pulling the distributor up at the same time.
Last edited by BigAl33; 17-05-11 at 22:10.