OK, enough dreaming. Back to work.
Chris, two things: Pump to cam drive contact and/or cam walk.
Pump to Cam drive contact: If it is the pump then the drive and the cam will have wear on the tip of the pump drive and the bottom of the cam bore/slot. Not the edge of the drive but the end and bottom in line with the shaft. Take a good look Chris it may be hard to see.
spade drive, pin derive or star drive.http://www.minisport.com.au/category22_1.htmhttp://www.calverst.com/articles/Eng-Lubrication-Oil_pumps.htm
Especially do not fit the pump until the cam timing has been done.
And for those who do not understand why us British car owners drink...
Another area of complication.
There are three types of oil pump drive: pin, spider and slot.
There are two pump shaft lengths, short for 850 & 998 and long for 1275.
There are 2-bolt, 3-bolt and 4-bolt pumps.
Early engines have 3-bolt. The later engines went to 4-bolt, but now the pumps most commonly available for 1275 engines are 2-bolt.
Now, you can fit a 2-bolt pump to an engine drilled for 4-bolts so long as the 4th bolt hole has not been drilled through into a waterway which, if the engine is an early 3-bolt type modified to take a 4-bolt later pump, it may well have been. If a threaded bolt hole has gone into a waterway and a 2-bolt pump is to be fitted it is vital to either drill out the pump casing to take the 4th bolt, or blank off the redundant hole in the block. If you don't you may get what I got on my Cooper 'S', 2 pints of Valvoline oil in the water!
Now I check each time before I fit an oil pump.
Also, the AP technical spec sheet lists the same pump for a pin-drive 998 as it does for a 1275. Whatever you do don't fit the 998 pump to the 1275 if you have a pin drive cam as it only engages on the pin by about 1/16" and will probably snap off with loss of all oil pressure.
There are two pump shaft lengths, short for 850 & 998 and 1100
and long for 1275 and the 970 and 1071 blocks
its a common mistake for people to stick a 850 pump into a s block (due to old cam drives and what not) and have problems with the drive shearing off. sometimes (dependant on the drive) the pump and the cam will 'just' mate so you thing its all ok, then when the timing gear starts to pull the cam back and forth in use it will drop out of drive and thats no oil pressure.
thats why i always advise to upgrade to a modern metro 'spade' drive cam and pump. then its easy, one cam, one pump either long or short nosed.
the trouble with the modern '2 bolt' pumps is that in stuff like old s blocks with 3 or 4 bolt fitting is that you will (or may) need to re drill and tap the block to accept the new pump. if you do this its important to cap the old unused bolt holes with cap head screws (as pete found out....)
as the old pumps go nla (like the cooper s one) is proably best to prep blocks to suit the metro spade pump whilst the engines in bits, as its solves any problems years down the line.http://www.hi-flow.com/HP012cVT.html
Interesting to read about installing different pumps and creating leaks between oil and cooling systems.
Cam Walk: How are the lobes tapered on your cam? like the GM forcing the cam to the rear?
A flat tappet cam having tapered lobes force the cam to the rear (GM 60 degree V6)
Your cam is moving to the front leading me to think the cam is walking even though it's not supposed to happen with a flat tappet cam.
Cam walk and a test. http://www.iskycams.com/pdfcatalog/2004-05/page192.pdf
Hope this helps.