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MG Midget and Sprite Technical - PCV Setup with Weber DCOE

I just rebuilt a 1500 engine for a friend, and am currently road-testing it and fine-tuning. It's fitted with a Weber DCOE (the side-draft one), and there was no PCV arrangement previously. I fitted a hose from the rocker cover to the air filter backplate, but have noticed after a drive that oil is being pressured out of the dipstick tube and a couple other places.

So, question... have any of you used the DCOE, and if so, how did you arrange for crankcase venting? Note that this installation uses a Cannon manifold that's equipped with a vacuum port... currently unused, and plugged. If I route a vacuum hose to that port, would I need a restrictor? If so, what size orifice?

Here's a photo of the installation:

http://www.flickr.com/photos/safety_fast/9102089891/in/set-72157633873660685/lightbox/

Thanks!

-:G:-

PS: Don't tell anybody, but this is on a Spitfire. ;-)
Gryf Ketcherside

Generally, when a Weber is fitted most people simply vent to atmosphere via a catch tank. However, this does lose the advantage of oil leak reduction that the slight vacuum of the closed system achieves.

Excessive pressure in the crankcase usually calls for checking the piston ring seal.

You could fit a closed breather system to see if that is enough to sort it, but you'll need a valve in there. Direct connection would see the sump contents sucked trough into the inlet tract in very short time, accompanied by clouds of smoke from the tailpipe. I wouldn't trust a restrictor either, but would fit a purpose-designed PCV valve.
Paul Walbran

Thanks, Paul... I may just leave it as-is for the time being, or drain the vent into a catch bottle temporarily. I consulted a friend who has some experience with a similar setup in his midget, and he said that right after the rebuild his engine oozed oil in a similar fashion until the rings had bedded in, at which time the blow-by apparently diminished and the leakage dwindled and finally quit.

Cheers,

-:G:-
Gryf Ketcherside

This thread was discussed between 26/06/2013 and 28/06/2013

MG Midget and Sprite Technical index

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