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[Spridgets] Sucking oil through PCV valve

Subject: [Spridgets] Sucking oil through PCV valve
From: davriker at nwi.net (David Riker)
Date: Mon, 17 Jan 2011 20:31:41 -0800
References: <4D349FD3.6090805@cox.net>
Dave
If this has been happening since the first day the engine was de-smogged, 
then the setup is wrong.
If it just started happening, something changed.
The PCV system is designed to apply a slight vacuum to the crankcase and 
serves two functions:
1. To remove exhaust gasses that slip past the rings and valve stems into 
the crankcase and
2. To prevent major oil leaks in the engine by preventing pressure from 
building up inside the crankcase.

A PCV valve is mostly a check valve, to prevent backfire flames from 
igniting gasses inside the crankcase.
A hose from the timing cover through the PCV valve and connected to the 
intake manifold pulls FAR too much volume of air, and winds up pulling oil 
out of the crankcase.  Having a vented cap INCREASES the ease at which that 
volume of air can be pulled.
The system I have been able to get to work is this:
Sealed cap
No vent in the valve cover at all.  (This makes it so the only air that can 
be pulled out of the crankcase is pulled IN through the scroll seal at the 
back of the engine, and any blow by that makes its way past the rings).
Hose from can on front of timing cover
Insert a plug into the hose at the top end, and drill a 1/8" hole in the 
plug.  This gives you an orofice to restrict the volume of air that is 
pulled out of the crankcase.
Hose connects to the british diaphram style PCV valve, mounted to the intake 
manifold.

If the car still belches oil out the rear main seal or dip stick tube under 
heavy load, increase the hole size in your orofice to 3/16 and try again.
If the car still belches oil out the rear main seal or dip stick tube under 
heavy load, increase the hole size in your orofice to 1/4" and try again.
If the car still belches oil out the rear main seal or dip stick tube, you 
probably have bad rings or a broken ring causing excessive blow-by and 
excessive crankcase pressure.

If you are running 20/50 engine oil and you experience oil fogging that 
begins about 2 minutes after you start driving but clears up after the 
engine has risen to opperating tempurature, try running 10/40, or even 5/30 
oil.  I had an issue where the thick oil wouldn't drain out of the head fast 
enough, and would then be pulled in via the valve guides and burned.  The 
thinner oil drains from the head faster and won't fill up the valve cover 
like the thicker oil can.
David Riker


----- Original Message ----- 
From: "David Ambrose" <stargazer1 at cox.net>
To: <Spridgets at autox.team.net>
Sent: Monday, January 17, 2011 12:00 PM
Subject: [Spridgets] Sucking oil through PCV valve


> We have a desmogged '70 Midget. It has the earlier carbs without the 
> vacuum intakes for crankcase ventilation and has been fitted with a PCV 
> valve. It's taken to pulling oil into the carbs via the PCV valve. The 
> valve itself seems OK, but I can't think of any other reason for the 
> problem. We've already been through the sealed vs. vented oil filler cap, 
> and have a vented cap on the car.
>
> Any ideas appreciated. I don't particularly want to order another PCV 
> valve for no good reason.
>
> Thanks,
> Dave Ambrose
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