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MG MGB GT V8 Factory Originals Technical - SD1 PCV Valve Conversion

I have converted the breather canister which screws into the tappet cover for the fitment of a PCV valve which will be plumbed into the Edelbrock carb.

Will the small breather in way of the tappet cover be sufficient to supply air "into" the engine or do I have to plumb this breather into the air cleaner noting that the 14 inch Mr.gasket has provision for such a connection.

Thanks Trevor Burnett
t burnett

V8 SD1 blocks need lots of breathing capability. It's not unknown for crankcase pressure to blow oil seals and cause the valley gasket to flap! At least plumb breathers from BOTH rocker covers to the air filter, with an additional filtered breather on one cover.I started off with this arrangement, but when I put a K & N filter in, I didn't like the idea of chuffing oil vapour near my new filter, so I put an oil catch tank in and modified the oil filler with a filtered breather. By the way the MGV8 had a filtered crankcase breather in addition to the two rocker breathers plumbed into the SU's. Will send you photos should you wish.
Allan Reeling

Here's the current set up.
Allan Reeling

PCVs need to be plumbed into the inlet manifold, or at the very least the manifold side of the carb butterfly. The PCV reduces the higb level of inlet manifold vacuum to a relatively constant low-level at the crankcase. That sucks on the crankcase, you then need air inlets elsewhere on the crankcase to provide a flow of air for extraction of fumes and condensation. These can be filters - which if the PCV is sucking on one rocker cover the filter would be on the other (twin SUs suck on one rocker cover each and there is a filtered inlet on the back of the block) - or instead of a dedicated inlet filter the 'other' rocker cover can be plumbed to the area between the carb and the intake filter. This allows filtered air into the engine without the use of a separate filter, and also allows any fumes ejected from the breather intake, which can happen under full throttle or a backfire, to be sucked into the engine and burnt rather than blown out to atmosphere. This is the more modern 'closed circuit' crankcase breathing system as opposed to the earlier 'through flow' system.
P Hunt

Thanks Al,set up not posted.
t burnett

I've tried to post a photo, twice now. The site says it has uploaded successfuly, but no sign of it..........lost in the ether??
Here goes again.

Allan Reeling


looking to your picture I am wandering what is this silver thing in front of radiator (second radiator)?

Toni Kavcic

No, it's merely a sheet aluminium shroud/fan guard. My reasoning was that if I was going to make a fan guard, it might as well help direct more air through the rad!
Allan Reeling

This thread was discussed between 09/01/2010 and 12/01/2010

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