MalP
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| posted on 30/8/25 at 07:32 PM |
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Crank case ventilation and emissions on a Zetec engine
I am converting my 1.8 Zetec Silver-top engine from Weber 40's to ITB's controlled by an Omex 600 ECU.
Q1 Can I remove the crank case positive ventilation box on the RH side if the bloc and fit a blanking plate?
Q2 Is it necessary to have an catch tank for oil fumes emitted from the outlet on the cam cover or will a small filter attached the stub pipe be
OK?
Malcolm
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coyoteboy
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| posted on 30/8/25 at 09:20 PM |
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It will likely be fine but you will lose some herspers to extra windage losses.
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Andrzejsr
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| posted on 1/9/25 at 06:53 PM |
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I have made a mistake and removed crank case positive ventilation box on my track Weestfield. changed to plate with tube, tube to oil catch can
(second inlet to cactch can from cam cover).
Before that silly decision I had almost no fumes/oil in catch can, and no leak around dipstick. After - on every trackday need to cleat oil arounbd
dipstick and afer few trackdays there is some oil/dirty fluid in catch can. That would be fine if not that oil mess around dipstick. And it is close
to hot exhaust manifold.
Leave that ventilation box, connect its out to catch can, also connect out from cam cover to this catch can. Clean catch can once a year and all will
be good.
https://aswestfield.wordpress.com/
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cliftyhanger
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| posted on 2/9/25 at 08:38 AM |
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It depends....
I fitted a blanking plug, but got a lot of oily smells in the cabin.
I then added a 1/2" pipe out of the blanking plate, up to a catch tank. Seemed better, but when I did a trackday and spent time at high rpm (over
7K) the catch tank filled with oil. The OEM oil box thing is clever, I would keep it. (mine is back on)
I have the outlet of the catch tank going into my airbox, very old fashioned but effective at reducing oily smells to zero
I am changing my EFI to single thottle body over the winter, and will then incorporate the original PCV valve. OEM setups tend to work way better than
what some bloke down the pub reckons. And racing setups are fine for that, but not very good for more regular use. My car does over 5K a year, a few
trackdays, plus at least one tour Alpine/Dolomite passes. So a real jack of all trades.
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Andrzejsr
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| posted on 2/9/25 at 11:02 PM |
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Yes! The same experience with high rev engine on track . oEM vent box is waiting to be installed again in my track Westfield. Happy i have not blanked
IT in road Westfield . Keep this part attached . Not much weight gain for sure troubles
https://aswestfield.wordpress.com/
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Charlie_Zetec
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| posted on 9/9/25 at 07:40 AM |
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Tin of worms here....
The original PCV valve in the casing that mounts to the block was fitted to assist with emissions and the re-circulation of crank case fumes (I think
primarily for the European market) to the intake system, and was vacuum operated. Unless you're running the OE inlet and pipework, it won't
operate properly; a lot of people often remove the valve and keep the casing with an external breather as it allows for any expelled oil to drain back
into the sump from memory.
I'm pretty sure some of the well-renowned engine builders for Zetecs (Scholar, Raceline etc.) say that blocking off the block breather isn't
an issue, as long as the cam cover is vented - usually via a small circular filter, or a catch-tank with breather on it.
I've purchased (and this is only a personal thing, and have no relation to the seller!) a block mount that has an angled output on it from Kinzy
Fabrications *HERE*, which I will be taking
to a baffled catch tank along with the rocker cover outlet. The tank has multiple adaptors - rocker cover to upper attachment, and I am considering
whether to mount the crank case pipe straight to the bottom attachment to allow for oil to drain straight back into the sump, or if i use a higher
attachment and feed a second pipe back down with a manual valve so that I can manually open and drain back after any spirited driving. If you look at
the design, it seems to have some thought behind it to allow venting without being overly 'open' into the crankcase.
FYI, I'm building a supercharged blacktop Zetec with a target power output of 320-350bhp on a single TB plenum input, so also have the option to
vent back to inlet - but will probably save that port some some methanol! 
Artificial intelligence is no match for natural stupidity!
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baz-R
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| posted on 24/9/25 at 01:38 PM |
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ex automotive engineer here
crankcase ventilation is often overlooked how important it is and one of the reasons engines last a lot longer and leak a lot less
on warm up our combustion is taking fuel (HC or hydrocarbons) and burning it with air (O2) and you get water (H2O) think water dribbling out the
exhaust on warm up. this works its way past the rings plus unburnt fuel.
PCV or positive crank case ventilation was a breakthrough and basically requires clean filtered air (often from air box) to pass into one place in
the crank case (often lower) and be drawn out from somewhere else (often upper cam cover) and pass into the inlet manifold to be burnt off (unburnt
fuel and any moisture exits the crankcase) in a metered way below atmospheric condition (anywhere under max throttle)
you also gain a lower air pressure in the crankcase reducing oil leaks and the combustion blow by been evacuated out prevent the chance of the oil
getting acidic and carbon build up increasing the time oil life span or service intervals.
there is also claims that a lower air pressure in the crankcase reduce aerodynamic drag on the crank but i suspect it so little i couldn't be
noticed
the race boys don't leave the oil or engine in the car to worry about it and old classics have a real short oil change interval
i built mine into my ITB setup and i would say if you can retain it keep it especially on road use cars
also if you are carrying out any form of motorsport you can still have a filtered vent on your catch can and keep pcv
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