MGB oil pressure problems. Easy fix or time for a rebuild?

A 73 MGB comes into the shop with the owner complaining about it having lower oil pressure that it normally has. I investigate to find out if there is a gauge problem, or if it really did drop oil pressure and has engine problems.
My findings may be surprising to some.

[@hueyhoolihan582]

nice to see someone that is looking out for their client's best interests! as there may be no point spending money on a car or engine that's on it's last legs. i have never thought of fuel in the oil as a cause of low pressure, but it sure makes sense. i'll have to make a note of that! and it always surprises me when people that own cars with manual chokes are pleased that their car will willingly start without its use. even on most summer days, i expect to have to pull the choke on startup and expect the engine to bog if not left to warm up for a minute or so before closing the choke. personally, i prefer a manual choke on carbureted cars. as i've never owned a carbureted car with an "automatic choke" that worked well, or worked well for long. and that includes the one on my Honda ST1300 motorcycle and the one on my '67 Jaguar Mkii. neither work well. and are from an engineering POV it is no wonder. the name "Rube Goldberg" comes to mind. the manual chokes on my current '53 TD and the one i used to have on my old '61 MGA and Yamaha 1100 motorcycle never failed me!

[@jeffhildreth9244]

The culprit was glaringly obvious in 3 seconds; POS Downdraft Weber. They are inefficient (90% bend) stock jetting from Moss and others is a compromise default. Proper jetting only possible with a dyno and a sack of jets. Solution, SUs.

[@crumblefest]

Amazing. If this solves my problem I will be writing odes of joy about the MGB guy...

[@mgbgtguy]

I hope your fix is as simple as this one was

[@MGB-learning]

Outstanding video and presentation.

[@wedjr97]

My Dad bought a 71’ B in 1980. It had no oil pressure then and it still will go from 50 down to zero in ten minutes. And yet,,,, I’m still driving it.

[@duncanwilson9020]

I have a 1970 mgb gt and just got her running, i replaced the oil pump in novermber of last year and when i tried to prime it i got a flutter from the needle. Now though i cant get any pressure on the guage no matter how hard i try. Furthermore i just replaced the oil cooler and lines, and cranking the engine helped me to bleed out any air pockets. Should i run the engine longer to allow oil pressure to build?

[@mgbgtguy]

I wouldn’t. It is quite common actually to put the wrong gasket in when putting in a oil pump in as the lower gasket set comes with two different gaskets. One of them is for the three main bearing engine, and the other one is for the five main bearing engine, if you put the three main bearing Oil pump gasket in, against the block It will look like you’re putting the right one in but you will get no oil pressure. You need to match the gasket to the pump not to the engine block. You need to be sure you put the right gasket in before you actually run the engine.

[@mgbgtguy]

Actually, you never want to run the engine before you verify you have oil pressure in the first place

[@5556ranger]

Mobil 1 15w 50

[@mgbgtguy]

I usually use Valvoline VR1 20w50 as it's so readily available in this area, but in this case I used Castrol GTX Classic 20w50 as it is a little cheaper, and I didn't want to spend as much of his money if my hunch wasn't correct and there really was an engine problem