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MGB-GT '68 BGT - Oil Pressure

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Lynn Kirkpatrick

Lynn Kirkpatrick

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So, I'm driving along in my '68 MGBGT with a '74 motor, all warmed up after 20 miles, and I notice the oil pressure seems to vary. I realize/expect that at idle the pressure will be around 25 psi. But at steady speed (40-50 mph, 2-3000 rpm) I can see the needle float between 20-30 psi. If I liftoff the throttle the pressure rises momentarily, then drops to 25. When cold, the pressure is 60-75 psi.

It has a pressure sending unit, not a pressure switch, the two choices in the Moss catalog. I have cleaned the connection on the sending unit, but haven't driven it to see if that helped.
Any other suggestions?

Lynn
 
That sounds a bit low to me. Assuming the sending unit is reading correctly, you could be due for an engine rebuild. How many miles you got on your B?

Anyway at freeway speeds (55 to 65mph) you should be able to maintain 50 psi +. Idle ~25-30 psi after the engine is warmed-up.

I know my 78B’s engine runs about 65 – 70 psi at 70MPH without any problems. But I have over a 120K on that engine and am getting ready to rebuild before I add some performance upgrades. Might even consider punching out the engine to 2.0L.
 
Your oil pressure readings sound about the same as mine did before rebuild. My engine only had 46k miles at rebuild and while the rest of the engine was in near perfect shape and almost no wear with 2 big exceptions. The first was the oil pump which was absolutely trashed and the camshaft had a few of the lobes worn off which I guess is fairly common with the later engines.

If you find your gauge to be accurate you may want to remove the oil pan and take a look at the oil pump, cam and how the bearings look along with the general condition of everything else.

My 46k mile oil pump

pic039.JPG
 
The electric oil sending unit is notorious for going bad. A new one costs $$$, and more then likely will be bad (I went through 2!). I finally swapped over to a direct pressure sender. Make sure you check the pressure with an outside source before you start fooling with the engine
 
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