Bit of technical help required, I have got an oil cooler that I intend to fit to my car (The block that fits to the engine is off a series V?) and the pressure relief valve within it is very worn, (I have ordered a replacement) additionally the spin on canister block currently on the car also has a relief valve can one be removed as surely you don't need to have two! Or is the one in the cooler block purely so you don't over pressure the cooler and pipes? Am I making sense or confusing you, your advice would be much appreciated.

You need both relief valves in the aluminium block which mounts on the engine block and carries the oil filter. One limits the engine oil pressure (it opens from about 40psi on the 1725). The other (admittedly less critical) acts as a by-pass for the oil cooler when the oil is cold and thick and doesn't need (or want) cooling. Rootes could have fitted some sort of thermostat, but they chose this other method.

Thanks for your help are they the same valve as I want to replace both as I will have the blocks off the car??

Just had a look at the valve in the car it is the brass type with thread next to bolt head so do you or anyone know who could supply it and the long one in the cooler to engine block???

Sorry, I don't know where to find one. Try ringing BSAC (John Hayter).
You might also check the US Alpine forums as they have long been obsessed with 'LOP' (low oil pressure) and devised some home-made mods to increase it. I haven't tried these.
I can tell you that the most critical thing in the main valve is the leakage past it when closed. If it leaks, then at idle, oil will pass this way rather than get up to the rocker shaft. So the piston should be a good fit in the tube.
If the oil pressure quickly rises to 40 when you rev up, and then hardly goes above this figure (except when cold), the spring is OK.

I have ordered the replacement oil cooler bypass valve from Cris Draycott. The relief valve, I just wanted to replace as I would have the mounting block in bits whilst putting the oil cooler on the car. My car has good pressure 50 psi but on a long run and when the oil is hot it drops to 30-35 psi ish. This is mainly with an OD that has recently been fitted the revs are lower, hence the idea to fit an oil cooler. Chris advises me that the later oil pressure relief valve is more reliable (There are two types, one brass with thread next to bolt head and the later one is thicker with the thread at the end like a normal bolt) so I am exchanging the oil filter block to the later type too, again supplied by Chris Draycott. Thanks for the advice on this matter the only issue I have left is the fitting of the cooler bar to a Series 3. If anyone has a good and simple method their advice would be most appreciated.

You say you have 30-35 when hot. If this is at idle, or below 2000rpm, it's fine. If hot it never gets above 35 even at high revs, you do have something worn - maybe the relief valve. If not, then probably the pump or bearings. I assume you are using 20W 50 oil and not something new and thin such as 10W 40.
There is no way to sugar this pill!

I am running the car on Castrol Classic, when hot (Motorway run) it is down to 35 at about 2500 revs 3500 will see 40 - 50, and tickover is about 15, (25 - 50 with cool oil pottering around town), before the overdrive it was running 40 on the motorway as the revs were 3000+, with the new valve and the cooler installed, if I still think the pressure is a little low I will recon the pump and have a look at the shells, the engine is the original with I think original shells, no knocks on start up and little to no smoke and the revs dont drop much when the clutch is depressed at idle. Any tips on fitting the cooler bar? Lastly thanks for all your advice.

The SV oil cooler is mounted in front of the radiator, with its upper edge level with the flat lower surface of the main air intake (so it takes in air from the intake below the bumper). This is good because it doesn't obstruct air to the hot top of the radiator. The cooler passes above the box section surrounding the starting handle hole, and is mounted in a simple flat bracket spot welded to the horizontal surface of the intake at each side. You could drill from below for pop rivets or bolts to fit similar mounts.
The pipes come upwards.
You could provide mountings at the same points off the radiator lower mounts by trapping them between the rad and the cross panel.

Incidentally, don't assume that either your rev-counter or speedo is accurate! With OD but the non-OD axle (3.89), 3000 rpm in OD 4th is about 68 mph (with 165x13 tyres). If you have the OD axle (4.22) 3500 is 71. You can use the posts at 100m intervals on dual carriageways or Mortorways to check your speed (16 for a mile).

Jon
I don't understand why you want to change the pressure relief valve if its working OK, unless the new valve has been modified you'll be dropping your oil pressure to 40 psi with the change.
It was the early 40 psi valves that initially caused engine failures and gave rise to the reliability worries. Rootes actually reverted back to using the earlier brass 50 psi valve for a while until the problem was resolved.
As for the oil cooler the Series 5 cooler is not the most effective cooler ever made, I think I'ld opt for one of the finned radiator types if I was seriously looking to cool down the oil, which incidently would also be much easier to fit.
My 2p worth
Pete

I was told the later valve was more reliable?? You can’t get the brass type so I am led to believe?? I didn’t realise the brass type was a 50 psi valve, but it is a case doing your best. If new valves and cooler don't improve matters as stated above the next stage might be having a look at the pump, plus there are so many mixed reviews with regard oil pressure

What is normal with a hot engine (50 miles plus of motorway use on a warm day).

Mine is........

15psi 750 rpm
30-35 2500rpm
35-45 3000rpm and above

1600 Series 3, 55k miles and all original??

Info from others would be informative with comparisons between old and new engines.

Cheers Jon

New oil cooler fitted, new oil pressure relief valve fitted. 40 psi at tick over and 50 psi at 3000 rpm, even when hot, so my tip is if the pressure is low change the oil and filter and replace the valve, well it worked for me.