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MG MGB GT V8 Factory Originals Technical - V8 Conversion - low L.O. Pressure

I have almost completed conversion with 3.5 ltr rover engine from a 1984 Range Rover. I have fitted L.O. filter remote adaptor and running with oil cooler. Noted that oil pressure low with slight tappet knock if engine left at idle - insufficient L.O. in rocker covers - will clear when increase RPM and therefore L.O. pressure. Can anyone advise if been down same route and options to improve L.O. pressure.

Regards, Sacha Cornell
Sacha Cornell

Have you checked the oil pump for wear. Basically remove thepump cover body and put a straight edge across the gears. Measure how much the gears stick out from the body with feeler guages. Can't remember offhand what that figure should be (someone help me here) but you can buy thinner gaskets from the specialists. Wear can be either in the gears (cheapish), the cover body (more expensive) or the engine front cover (even more expensive). The cover body can be "fixed" by flatting down the wear surface with sandpaper on a sheet of glass. Good luck
Stuart Robson

Sacha

Some reconditioned gauges do give a false low reading, and Rhodes lifters can be noisey.

Using M1 0W40 the hot idle is 25psi.

Real Steel do sell a reversing plate to increase pressure.

Paul
Paul

adjust idle to 800 rpm - change pressure relief spring (available over the counter) to gain 4psi - measure accuracy of the guage by taking a reading at start up -then start worrying about the pump. You will be looking for 46psi at start up with the HP spring (and never less than 20 at very hot idle).

Let us know how you get on

Roger
RMW

On my '71 car the oil guage read 10psi at idle when cold & 0psi when hot I had the guage serviced & now it reads 40psi & 15psi.The instrument mechanic told me that the old dual guages were not very reliable anyway. On my '78 car which has a single type oil guage, I get 70psi cold & 40 psi cold. FWIW. Barrie E
Barrie Egerton

The clearance between the gears and the pocket face should be .0018" i.e. 1.8 thou.

The engine is usually described as 'low pressure, high flow' and too high a pressure can be detrimental, actually eroding the bearing material in extreme cases. The factory V8 oil pressure is given as 'normal' 42psi, idling 34psi. Most seem to give significantly less than that at idle and it is very susceptible to ambient temperature, I have seen that 34psi immediately after a run in cold weather, but it can be as low as 15psi stuck in traffic on a hot day. Roger Parker said Police experience was 'What hot idle oil pressure?'.

Worn hydraulic tappets or bores can cause tappet knock and low oil pressure, and low oil pressure and worn tappets can cause knock - a bit 'chicken and egg'. If there is no visible oil around the rockers (especially the left rear) at idle then that *does* tend to confirm very low oil pressure irrespective of what the gauge is saying, which is easy enough to confirm with another gauge. I don't know about dual gauges being inherently unreliable or even innaccurate, although the latter is more likely with a poor rebuild.
Paul Hunt

This thread was discussed between 27/02/2005 and 01/03/2005

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