Welcome to our resource for MG Car Information.



MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Emissions Valve

Just spotted an emission valve on Ebay. The seller says it was listed for the MGA and early MGB.

How did it work? Was it ever fitted to export MGAs?

Steve Gyles

Its a Positive Crankcase Ventilation (PCV) or anti-backfire valve for use in closed circulation crankcase systems. They were never to my knowledge used on the MGA.

PCV is a system where the sump gases are fed into the engine and burned rather than being vented to the atmosphere. The pipe to the air filter on the A is a partial system but the one introduced later (by law from 1963 in the UK I think) connected the sump to the engine side of the carbs. Because the vacuum in the manifold changes with throttle opening the PCV valve is fitted to regulate the gas flow. It is also designed to stop a backfire from igniting the oil vapour in the sump.

Malcolm Asquith

Had one of those on my midget. The rubber split and made some impressive smoke screens from the exhaust. Was on the verge of planning an engine rebuild when I found it!
Neil McGurk

Except in California, where it had been used for two years previously, General Motors didn't ship its PVC valve until 1963. It seems inconceivable to me that a PVC valve was ever installed in a new MGA.
Ken Korey

Neil, had the same thing happen on my series 3 Land Rover and used about half a gallon of oil in 20 miles!
Lindsay Sampford

PCV valve first used on MGB in early 1964, about 40% of the way through 1964 model year production. Never used on MGA. If you do a proper job of retrofitting one on MGA it may reduce oil leaks, because it draws a slight vacuum in the crankcase (but you also need the proper sealed oil filler cap and restrictor orifice for the valve cover inlet vent).
Barney Gaylord

This thread was discussed between 28/12/2009 and 29/12/2009

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.