3.9 - Low Oil Pressure ( ,  )

Peak pressure should be somewhere between 45 and 60psi. The standard specification is 40PSI at 2000RPM. A low oil pressure reading can have several causes. The simplest to fix, and most common is the failure of a pressure transducer (not applicable to Mk 1 with mechanical pressure gauge). You can check this by connecting a mechanical pressure gauge to one of the ports in the oil gallery (brass plugs low on the side of the block). If the pressure reads normal on the mechanical gauge, replace the transducer.

If the pressure still reads low, there are a couple of more things to check. The oil filter body has a bypass valve and a pressure relief valve. When the filter becomes overly clogged the bypass opens. If the pressure from the oil pump is too high, the relief valve opens and returns oil to the pan. If the spring on this valve has become weak, it can open early, resulting in lowered pressure. A symptom of this is usually decent idle oil pressure which rises slightly with RPM and then stops changing. You can either replace the spring, or shim the seat on which it sits. Some fiddling will be required to get it right.

If the pressure is still low, you have a problem either in the oil pump itself, in the pickup tube in the sump, or in the engine bearings.

3.9.1 - Using a S2 XJ6 Oil Filter Head on a MK2/Stype ( Burdo/Hand,  June 28, 2005 )

S2 XJ6 Oil Filter Head, non-oil cooler model

The filter head from a XJ6 S2 with the top vertical fitting filter fit
the early saloons. I noted that in Paul Skilleter/Jaguar World XK150
restoration book he makes mention that he went from the original
canister style oil-block set-up to a 4.2 S2 XJ set-up. There is a
picture of it on page 99 of his book, picture 5. The filter head shown
has the BL logo on it and the id# starting with what appears to be a
backward ''9''followed by 44282A.

Nick Hand adds:

The series 11 works, from the 76 77 year models . I have one
on my 67 S-Type. It takes a vertical filter[spin on wix # 51231]