Brad,
I guess there are tollerances quoted somewhere for rocker shaft wear. On
mine the shaft had distinct wear ridges, and the case hardening was breaking
down in high pressure areas. If you start the car with the rocker cover off
you can see just how much oil is leaking out from the rocker bushes. I got
another shaft from the local scrap yard which looked a lot better and had
very little wear. It certainly slowed down the excessive flow of oil.
In theory, the exhaust valve stems should not suck oil down them as when the
valve is in the open position, the piston is rising to dispell exhaust
gasses. Opposite of the inlet valves which suck - if you get my drift.
However, it may have something to do with valve overlap. On mine oil was
certainly leaking down the exhaust valve stems and producing lots of blue
smoke. Oil seals stopped it. But don't put oil seals on the exhaust valve
stems if this is not the problem - they do need some oil. If putting seals
on makes no difference, then take them off again.
AND, you do not need to remove the head to do this. Use the string in the
combustion chamber trick . Easy to do and much quicker!
Quick way to check if the crankcase breather system is causing the smoke is
to disconnect it at the manifold. put a bung in the manifold orifice and go
for a drive. It will probably start to leak oil out of the crankshaft
"seals" but if it stops blowing out oil smoke then you have found your
problem.
Guy
----- Original Message -----
From "Brad Fornal" <toyman at digitex.net>
Cc: "mg" <spridgets@autox.team.net>
Sent: Monday, April 19, 2004 6:34 PM
Subject: Re: Rebuilt motor
> Guy Weller wrote:
>
> > The UK spec ones didn't use a PCV valve, just a direct pipe
> > connection to the carbs and they are not in the habit of sucking all the
oil
> > out of the sump by this means!
>
> I know that strong manifold vacuum "could" do possibly do this. How strong
it
> would need to be is something I don't know.
> I have another PCV valve that I had put on the old worn out motor, and it
had
> the ruptured diaphragm, and it smoked something fierce. Once it was
blocked, it
> didn't smoke anymore. I finally put in a standard PCV valve, with a few
nuts in
> the hose to "graduate" the orifice, and it smoked a little, but not near
what it
> did with a bad diaphragm.
>
> >
> >
> > I had similar problems on my part rebuilt engine a few years back.
Turned
> > out to be a combination of things.
> > First a worn rocker shaft, allowing too much oil leakage from the rocker
> > bushes and into the valve cover area. Changed that and it was a good
deal
> > better, but...
>
> How does one determine what is "too worn" as I have a large selection of
used
> rocker shafts on the shelf.
>
> >
> > Secondly, my engine was pulling too much oil down the exhaust valve
stems.
> > I know it shouldn't do that, but the eventual cure after much
experimenting,
> > was to add those little oil control seals to the exhaust valve stems as
well
> > as the inlets.
>
> I have some stem seals, so perhaps I may pull the head after I try the
diaphragm
> and rocker shaft first.
> Thank you for the suggestions sir.
>
> Brad
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