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MG MGB GT V8 Factory Originals Technical - Oil pressure when braking hard


When braking very hard I have noticed that the oil pressure drops to zero and then back to normal. Presumably this is caused by the oil moving away from the pickup strainer.
Has anyone else experienced this and what is the best way to cure the problem. The sump is factory GTV8.


Mark
Mark Rawlins

This is probably caused by oil being forced away from the pickup, starving the pump. It can also be seen during hard cornering. You can experiment with various designs of baffles and trapdoors to help keep the oil in the sump during high g-load manuevers. The design of these is kind of a black art that usually involves the consumption of several sets of bearings before stumbling into a workable design.
Maybe a better option is a hydraulic accumulator that will discharge pressurized oil into the engine upon momentary loss of normal engine oil pressure. These are available through many mail order race suppliers.
AD
Art Dodge

I expect you’re right about the cause. Two modifications to the oil pan can help, but you know what that means, pulling the engine.

One thing that helps is to increase the capacity of the sump by having the rear notch removed. Cutting away that portion and welding on a new piece is what is required. As you decelerate, more oil moves forward to keep the pickup covered. I had this done and believe it or not, I lost the modified pan and had to buy another! The problem is the stock exhaust crosses over in the area of that relief.

The other thing that helps is to weld in a baffle above and forward of the pickup to hold the oil from rushing up into the shallow forward section of the oil pan during deceleration.

Art’s suggestion may also provide an option to pre lube the system before startup.
George Champion

Mark,

I as understand it Nascars have a secondary pickup to deal with banking. I know a couple of people who could point you in right direction. Flavour of the month with Rockingham.

Paul
Paul

There has been comment on this in earlier threads.

The oil accumulator, available widely in the USA, and from Real Steel in the UK seems to be the answer to this, enhanced lubrication at start-up, and other oil pressure/flow problems.

Safety Fast

Nigel
MGA 1600 Roadster
"Works" B GT V8
R V8
Nigel Steward

With the exhaust system removed it is easy to remove the sump. Later Rover V8 sumps have a small plate/baffle accross forward end of the sump - presumably to prevent the pressure loss described. The factory landrover engine had a strengthening plate between the rest of the engine and the sump and this may have had a similar effect with a full sump.

In 140,000 miles, I have not experienced pressure loss and yes - we do drive the car (now 3.9FI) hard - but before readers have a panic attack they might wish to take into account that the Buick/Rover lubrication system is closer to free fall than the pressure spray of less agricultural (and more modern) ICEs - the engine works with very little pressure for a lot of its city life and provided owners follow the maxim of regular change with reasonable quality oil they can expect long life.

Happy carefree motoring
Roger Walker

The oil accumulator idea is very sound. The type with the electric shut off valve is what I've found to work out the best for everyday use. Turn the ignition on, oil pressure!
I have documented doubling the engine life of ambulance engines that I used to work on. The pre-oiling is the key.
Installation is easy and will cost is low for what it offers.

Good luck!
Kelly
Kelly

Don't brake hard!
Mark

Think Ill try fitting an SD1 sump first as it has steeper sides.

Cheers

Mark
Mark Rawlins

This thread was discussed between 12/07/2001 and 21/07/2001

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