1979 Leyland Sherpa 230 petrol 1.7l with "O series" engine

I have an "oil separator" (or oil catch can) attached to the side of my engine. From there it goes through a hose to the ported vacuum by the throttle plate of an SU carb. Inside the hose is a pintle valve or what you might call a PCV valve today.

Well, it seems the hose with integral valve is now unavailable. So my question is do all PCV valves work the same? ie. close at high vacuum (idle) and opens at low vacuum (cruising speed) and closes with back pressure (preventing explosion in crankcase from a backfire). So can I purchase any replacement PCV valve so long as it is rated for a similar sized engine ie. 1700cc engine.

  • First point the oil catch can was not standard... So, that begs the question is that pcv valve part of the original equipment or just a bit that was handy when someone was fitting the catch can?
    – Solar Mike
    Commented Mar 10, 2018 at 9:32
  • Hi @Solar Mike . Not exactly sure what you mean by standard but I even have a part no. for it from a Sherpa parts catalogue. I have many reasons to think it is original equipment. The Leyland mini has a similar set up too. Commented Mar 10, 2018 at 11:05
  • How big is this catch can ?
    – Solar Mike
    Commented Mar 10, 2018 at 11:14
  • It's about 4 inches tall. It looks exactly (and possibly is) this 1 on ebay. ebay.co.uk/itm/… Commented Mar 10, 2018 at 11:17
  • @solar mike . see comment before Commented Mar 10, 2018 at 11:18

2 Answers 2


For a multitude of reasons, PCV is very important. Especially on those old cars, so i'd make sure it at least works. How it's done doesn't make all the difference. Some people use the SU carb's port to vent it off(later method), some use a pipe that runs down to the road, cut at an angle.(former method) Being cut at an angle, the pipe create a low pressure when air gets blown past it, venting the crankcase.

The former method makes gunk and oil deposits settle in your manifold and carbs, so the use of a catch can sure is recommended. I use an aftermarket one myself, too. Like many other cars, my car doesn't have a PCV valve, by the way.(76 Triumph TR7, also a leyland product with SU's) It vents the same at all times, and I never experience backfires or any other mixture related problems, either when disconnecting or using the PCV system. I don't think backfire issues normally occur when the PCV system is faulty, or when the valve is taken off or broken.

Theoretically, the PCV port on a SU only sees the vacuum present after the airfilter, so that's almost no vacuum. The valve in the PCV system is a minor drivability aiding feature, and removing or replacing it with a different one makes little difference, if indeed connected to the SU. If your PCV system is connected to the manifold though, it is a whole different story, and using a valve with a different spring rate may cause lean running.(and thus backfires)


According to Wikipedia, the BL O-Series 1.7L was used in:

  • Leyland Sherpa/Freight Rover Sherpa/200/300 1.7 L, 2.0 l
  • Princess / Austin Ambassador 1.7 L, 2.0 L
  • Morris Ital 1.7 L, 2.0 L automatic
  • Morris Marina 1.7 L

In case that helps in your search.

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