Crankcase breather, PCV etc.

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Crankcase breather, PCV etc.

Postby -JC- » Tue Mar 31, 2009 11:07 am

When I replaced the vacuum hoses I bypassed the PCV valve, but I left the standard crankcase breather into the manifold in place. Reading something the other day made me realise this is probably a bad idea - the breather is no-longer vacuum controlled, so I'm guessing this means that it's either venting fully open, or fully closed? So what's best to fix? Leave the PCV disconnected and fit a K&N style filter and run the pipe separately? Or re-fit the PCV withe ither the existing system or K&N type system?
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burtonm
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Re: Crankcase breather, PCV etc.

Postby burtonm » Tue Mar 31, 2009 7:58 pm

is the PVC that goes into the side of the engine still connected to the inlet manifold?
i'm not sure but i think that's the only one that's vacuum controlled.
mine has that, and just a vented oil filler cap, that never was connected to my air filter, even before i had a k&n.
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Re: Crankcase breather, PCV etc.

Postby Supercharged Nat » Tue Mar 31, 2009 8:44 pm

-JC- wrote:When I replaced the vacuum hoses I bypassed the PCV valve, but I left the standard crankcase breather into the manifold in place. Reading something the other day made me realise this is probably a bad idea - the breather is no-longer vacuum controlled, so I'm guessing this means that it's either venting fully open, or fully closed? So what's best to fix? Leave the PCV disconnected and fit a K&N style filter and run the pipe separately? Or re-fit the PCV withe ither the existing system or K&N type system?


i dont think the crankcase breather is vacuum controlled?- its just plumbed into the inlet manifold. which can be left as is or you can use a catch tank (once the inlet has been blocked off).
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Re: Crankcase breather, PCV etc.

Postby -JC- » Wed Apr 01, 2009 9:29 am

Hmmm, not sure now. I'll see if I can find the bit I was reading...

Burton Power wrote:With increasing environmental pressures Positive Crankcase was introduced whereby crankcase vapours were drawn up into the inlet manifold and, along with the air/fuel mixture, burned up in the combustion chambers. To enable this system to work safely and efficiently the ventilation from the crancase is controlled via a PCV valve. To avoid upsetting the fuel/air mixture the PCV valve must regulate the evacuation of these blow by gases and vapours (which will be minimal at idling speed but will intensify as engine speed increases) Since manifold vacuum is highest at low engine speeds the PCV plunger will be drawn forward to a position that will restrict crankcase ventilation to a minimum.....
(and vice versa I assume)
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Re: Crankcase breather, PCV etc.

Postby SmokeEm » Wed Apr 01, 2009 11:27 am

We replaced the pcv with an alloy block breather from ebay - £7 then fitted a Transit DCI filler cap with outlet. Plumbed into a T piece and ending in an alloy catch tank with K&N breather.

Sorted 8-)
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Re: Crankcase breather, PCV etc.

Postby -JC- » Wed Apr 01, 2009 11:51 am

So the catch tank feeds back to the engine via the filler cap? Or am I getting the wrong end of the stick?
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Re: Crankcase breather, PCV etc.

Postby Supercharged Nat » Wed Apr 01, 2009 4:32 pm

-JC- wrote:So the catch tank feeds back to the engine via the filler cap? Or am I getting the wrong end of the stick?


i think youve got the middle of the stick! ok here goes:

the pcv is fitted into the side of the block on a pinto (below the inlet manifold). it simply pushes into a seperate housing that fitted into the block itself. if you havent removed this valve then the pipe coming from it can be left plumbed into the inlet manifold.

if you have removed the valve, your engine is open to the atmosphere (and probably blowing oil vapour all over your engine bay).

I think your getting the small vacuum pipes on the carb/ inlet manifold confused with the crank case breather. maybe put up a couple of photos so its a bit clearer?
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Re: Crankcase breather, PCV etc.

Postby Terra-Kotta » Wed Apr 01, 2009 4:44 pm

open cap, open breather, or pipe off and run into catch tank, 1 litre castrol container if you wana be real old skool.

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Re: Crankcase breather, PCV etc.

Postby -JC- » Thu Apr 02, 2009 12:38 pm

Supercharged Nat wrote:I think your getting the small vacuum pipes on the carb/ inlet manifold confused with the crank case breather. maybe put up a couple of photos so its a bit clearer?


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Sorry, I might have worded it badly or got confused lol. I've removed the vacuum pipes (viewtopic.php?f=13&t=30405), but the actual breather is still in place. From looking at the haynes manual supplement, it looks like the metal bit behind the red circle is the valve that controls how much the vent is open, and the valve works on manifold pressure? Although I'm not entirely sure now, cos I can't see what the water pipe has to do with anything? I think I'll have to check the supplement again!
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Re: Crankcase breather, PCV etc.

Postby Supercharged Nat » Thu Apr 02, 2009 4:16 pm

ok that jibblet in the red circle is not to do with the crank case breather. that jibblet is to do with emissions control. if i remember correctly it is connected to the dizzy via one pipe and the the enrichment device on the carb by another pipe. the brass bit that fitted into the water pipe is used to control the jibblet (depends on water temp as to when the vacuum effects the enrichment device/ dizzy).

going back to the thread linked into your reply, you basically just remove that jibblet, joint the water hose, and then connect the vacuum hoses to their respective areas on the carb (i think).

crank case breather is something entirely different....
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Re: Crankcase breather, PCV etc.

Postby Conor » Thu Apr 02, 2009 4:36 pm

Take off all those pipes and throw them in the bin. The red circle bit reduces the amount of vacuum pressure to the distributor vacuum advance. Don't need any of it as its just pointless emissions gubbins.

Look at the pictures below. You'll see I've got rid of it all and put a new bit of coolant pipe to go from the manifold to the autochoke.

All you then need to do is run a bit of vacuum pipe from the outlet at the base of the carb on the front corner nearest the inner wing to the union on the valve just above it and the vacuum pipe connector on the base of the carb under the automatic choke goes to the distributor vacuum advance.

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Re: Crankcase breather, PCV etc.

Postby -JC- » Thu Apr 02, 2009 6:41 pm

Ok, I did get confused then :oops: I did disconnect it before but when I found the PCV bit on burton power I got confused with this gubbins (PVS). Damn acronyms! Thanks again guys!

edit: Lol, jibblet!
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