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MG MGB GT V8 Factory Originals Technical - Oil temp and choice

Hi All,

The engine is running (hey!) and I'm gradually sorting out the problems, still fighting with upholstery and carpets etc.

I have an oil pressure query.

I'm using cheap 20/50.

When I got the engine in the donor SD1 the oil pressure was down to about 10 at idle and 25 at higher revs. This was with cheap 20/50 in it (I put it in).

One of the things I did when I took the engine out was to renew the oil pump gears.

Now the engine is running again the cold Start up idle pressure is 50-55 and fluctuates arund that when revving it up to 2000. I'm too scared to take it up 4000 to see what happens!

After 10 mins or so at fast idle it drops to about 20-25 idle, and 40 when revving.

Is this to be expected with new oil pump gears?
Will it drop back a bit with use?
Should I switch to a different grade of oil?

I have double checked these figures with a different oil pressure gauge. FYI I don't have an oil cooler.

Your advice would be appreciated.

Thanks, Liam
Liam H


don't worry, your readings are O.K., i have the same presures with the use of 10W40 with the same SD1 engine.

The oil temperature stays within the range of the coolant temperature after @ 20 to 30 minutes from starting cold. An oil cooler thermostate should be high on your list with the V8.

One point to check when changing the oil next time: Mesure the volume that is quoted for the SD1 sump (on the MG V8 the oilcooler and filter is topped up separately) and top it up.
Then check the mark on the dipstick and add a new one if necessary. When the engine is not exactly positioned the same way as it is in the SD1, there might be different levels shown at the dipstick and i had to recalibrate it on my car after i found out that there was a difference of nearly one litre missing.



I have filled the engine to the level indicated on the dipstick - it was less than the quoted figure, I think I was a couple of lites short - should I just add another litre or two anyway?

Liam H


The SD1 manual states 8.5 pints (4.8 litres) for the sump without filter.
The Rover V8 does not built up high presures but has a high volume circulation, so the oil level should always be close to the recommandations of the manufacturer. Remember, there is a lot of oil left in the heads and the lifter gallery during operation, so it should allways been filled up propperly.


The thought occurs to me that where I have the pressure take off may affect the reading.

At the minute it is on the outside of the gear cover plate on the engine. If this is after the pump then might the produce a higher reading than if I bought a sandwich plate for the remote oil filter and sited the take off there perhaps?

Liam H


the fitting on the line from the pressure gauge normally goes to the MG V8 oil pump adaptor. It is the side where presure is present and from this 'runner' oil is routed to the filter. Therefore the readings from a pickup at the filter are much the same.

I was also thinking upon taking pressure from the filter base (as done on the works V8) but as the readings were the same, i fitted a pressure warning switch there.
The filter base can be machined to acept a sender unit directly, as there are two carst on bosses that can be drilled and tappered for a fitting of a sender. I had this been done to the rear boss (where the flow enters the filter) by a hydraulic service for commercial vehicles as they are skilled for these jobs and it was cheap. The presure switch and an additional red warning light at the dash are a good investment for peace of mind, i think, as on the SD1 installation a switch at the pump was used to power the fuel pump only when presure was built up.



This thread was discussed between 08/05/2007 and 10/05/2007

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