Oil Pressure too high?

[MMT1968]

Hi guys,

My recently rebuilt 1275 Marina engine runs at an oil pressure of 8 bar at idle when cold and 5 bar when at normal oil temperature. The engine is tuned with high compression pistons to 10,3:1, a Kent 266 camshaft and fully ported head. I changed the oil pressure valve to a ball/spring of a 1275 Mini Cooper S. I wonder if this ball valve is the reason for the elevated oil pressure and think about shortening the spring a bit. But how much should I cut off?
Has anyone had faced the same or a similar problem?

Chris

[philthehill]

Only the oil pressure release valve regulates the oil pressure - all the other items referred to above have no bearing on oil pressure.
The increase in oil pressure when fitting the ball is quite normal. To reduce the oil pressure cut off one coil of the spring and try the oil pressure. If still too high cut off another coil and see what the oil pressure is then.
Further adjustment may be necessary. Put the cut end of the spring into the cap.
Using the standard spring with the 5/8" ball bearing may also help.
https://www.minispares.com/product/classic/6K853.aspx
The oil pressure when the engine is at normal operating temp and at medium revs should be around 4.5 bar (63lb).
To make the job much easier you could use one of these but you will still have to shorten the spring:-
https://www.minispares.com/product/Clas ... |Back%20to

[kevin s]

I found the ball and spring type to be far to high too, went back to the original bullet type, idles around 50psi now.

[MMT1968]

Thanks Phil,

I‘ll try it with cutting off one coil of the spring. Can you say how much the reduction of the oil pressure can be expected after cutting off one coil?

Chris

[mgdrf]

I had exactly the same problem. I fixed it by changing the oil to 10w40. I believe this was the recommended oil for late model Marinas.

[MMT1968]

I‘m using 10W40 already and have that problem though.

Chris

[mgdrf]

Perhaps a blocked oilway. Is the oil getting up to the rockers ?

[MMT1968]

When rebuilding the engine the oil gallery was opened and cleaned completely so there shouldn’t be a problem.
I changed to the ball type because of the common risk of blocking by the original system. As it works in Minis it should do so in a Marina engine as well. I guess shortening the spring is the easiest way to try to solve the problem. If it doesn’t work, I can use a new spring and try again or go back to the original valve instead.

Chris

[mgdrf]

I’m sure you’re right. I’ll be interested to see how you get on. I was looking for a quick fix because my car had so many faults that I needed to attend to. After four years of ownership it’s nearly reliable!

Regards, Dave

[philthehill]

I am afraid you will have to try the spring after cutting off the coil so as to determine the reduction in oil pressure.
You may have to remove a second coil to get the oil pressure right.
Not all springs have the same compression rate so I am unable to give a precise figure.
As suggested above try a standard or old spring and see what happens.

[MMT1968]

@ Phil,

…I will try first with the old spring. But I guess it will not work because that spring is longer as I remember than the one that hat came with the ball. But maybe it is a bit weaker.
It is a bit difficult to get to the domed nut in a Marina engine as the oil filter and the starter motor are blocking the way. Much easier to get to it if the engine is out.

Chris

[philthehill]

You are right in that it is difficult to get at the Marina oil pressure relief valve because of the oil filter and starter.
To overcome the difficulty I made a socket to pass over and behind the starter motor as per photo below.
The first stab is on the left and the revised socket is on the right.

oil press cover socket 2.JPG (777.06 KiB) Viewed 819 times

I will have a look at the spare oil pressure relief valve springs I have in the morning and come back on here.

I will also double check the ball dia in the morning as I have found a reference to it being 9/16" Dia.
Phil

[MMT1968]

@Phil

Another problem is that I have an oil pressure sensor mounted instead of the switch. These things are normally too big in size and diameter to fit in place as the oil filter is in the way. To overcome this problem I made a 90° stud the sensor is mounted on and elevated by this also. Due to this it now sits at an angle of some 45° backwards between the oil filter and the starter motor covering the access to the domed nut of the oil pressure relief valve almost completely. Nice. Should have thought about earlier but never expected to have to get there again.
I‘ll try it with a socket like you suggested but if I can not get to the nut this way I’ll have to do the job when the engine is out for the gearbox swap. I will not have to drive much with the car until I can do that job.
But anyway thanks for your advice.

Chris

[philthehill]

What I did was to mount the switch (or in your case a sensor) remotely away from the block because of the congestion around the area of the oil pressure switch.
If you want my original socket just PM me with your address and I will post it off to you. It uses a 1/4" square drive. Even though that is small it is sufficient to undo and tighten the spring cover nut.

[MMT1968]

Hi Phil,

Thanks, please see PM.

Chris

[philthehill]

To confirm - the ball is 9/16" dia.
This morning I looked at and compared springs/ball/bullet cup lengths. See photo below.
I would suggest that you shorten the original spring to give an overall length (with ball) of 76mm.

oil spring.JPG (97.83 KiB) Viewed 755 times

[MMT1968]

Thanks Phil,

That’s what I had in mind, the spring with ball is longer than spring and bullet. Using the bullet‘s spring would make it too short. This morning I removed the oil filter and got the pressure sensor out of the way. I guess it will work to get the domed nut out using your modified socket.
So I‘ll wait and be patient which is not my best ability .
But I have to wait for my range rover flame trap coming from the UK anyway. I want to include it in the crank case breather hose towards my vacuum pump, just in case.

Chris

[MMT1968]

Just for an update.
After having shortened the spring about 4mm the oil pressure gauge shows 7 bar when the oil is cold and some 6 bar at normal temperature. That’s Ok to my opinion.
Thanks for your input and the socket, Phil. That was a great help.

Chris

[oliver90owner]

You mean it runs at higher pressure, now, at normal operating temperature? Still too high, IMO.

[MMT1968]

Well, it is a seriously tuned 1275 Marina engine with raised compression to 10.3:1 and similar treated 1275 Mini engines are usually run with 7bar at 90°C oil temperature.
So I‘m more or less satisfied with the oil pressure as it is now. Prior to shortening the pressure relief valve spring the engine run with 8 to 9bar. That for shure is too high.

Chris