The MGA With An Attitude

You may wish to review the prior article about function of the pressure relief valve.

The attention grabber here is the open port "E" in the lower picture. This is where oil will return to the sump after passing over the pressure relief valve. If this port is plugged it will defeat function of the pressure relief valve, and the engine will have excess oil pressure any time the pressure relief valve should be open. It might have 100 PSI oil pressure at idle speed with cold oil. When hot it may have 100 PSI or more oil pressure at higher engine speeds (3000 RPM or higher). It could even develop enough pressure to blow out an oil filter seal or to burst a spin-on oil filter canister.

  oil flow diagram photo, left rear corner of engine block

I see occasional messages noting this problem after a professional engine shop worked on the engine. The oil gallery plugs are commonly removed before hot tanking so the drill holes can be checked and cleaned out with rifle brushes. After machining of the block and a final pass at cleaning, the oil gallery plugs are replaced. Even a pro shop may occasionally make a mistake and plug the wrong hole. If port E has a plug in it, you need to remove it.

  oil flow ports, bottom of engine block, left rear corner

Thank you for your comments -- Send e-mail to <Barney Gaylord>
© 2011 Barney Gaylord -- Copyright and reprint information