Removing the MGB oil pressure relief valve – how a 5 minute job turns into a 3 hour task!

One disadvantage of spending three plus years restoring a car is that it’s easy to lose track of what replacement parts are purchased. I’ve been very good about labeling all of the original removed parts and putting them in storage and also keeping up with organized storage of the new replacement parts that I’ve purchased.

Of course, there are always glitches. I went to install a new oil pressure relief valve yesterday and couldn’t locate it. A good hour of looking and I had no luck finding it. The next step was to go through my orders from Moss Motors and British Parts Northwest to confirm that I had indeed bought a new relief valve. Guess what? I missed purchasing a new valve somehow.

50 years of MGB GT receipts
50 years of MGB GT receipts

No problem. I could always install one of the old pressure relief valves as I have 2 engines and theoretically should have 2 used valves. Wouldn’t you know, I only have 1 used valve from the original 18GB engine and it was missing the plunger. Perhaps the 18V I bought didn’t have a valve installed? And where was this plunger located? The plunger had to be located in the old engine block in my basement.

Of course, the plunger is deep inside the block and fiddling around with different tools failed top coax the valve plunger out. I got on the internet for advice about the problem and in general the idea was to hit the starter to rotate the engine and the oil pressure would blast the valve out of the hole, My engine block doesn’t have a starter attached and doesn’t have oil in it, it’s a stripped chunk of iron.

Tap inserted in MGB pressure relief valve bore
Tap inserted in MGB pressure relief valve bore

Out came the tap and die set. It turns out a 1/2 inch tap will lightly grab the plunger when inserted and makes the removal easy. Very cool!

Tap and pressure relief plunger
Tap and pressure relief plunger

If you’re wondering why I didn’t just head out and buy a new pressure relief valve it’s down to lack of availability, cost and very slow shipping times here on Vancouver Island in Canada. If I order from the my favourite parts outlet in Oregon it would likely take at least 3 weeks for the part to arrive. The last time I looked at ordering from them and shipping to Canada the cost was outrageous! If I could locate a part on Amazon even with Amazon prime packages are taking about 1 month to arrive. The chance of finding a part locally is about zero.

Anyway, I now have my part and it’s ready to be installed. It may not be new but that’s OK. Stay tuned!

MGB pressure relief valve
MGB pressure relief valve

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