There will always be blow-by. That is why there is a crankcase ventilation
system. It will usually be high in a new engine until the rings seat and in
older engines as they wear, but it can't be eliminated entirely. As for the
gases "moving up" the gases don't care which direction they move, they just go
in the direction of least resistance. The blow-by pressurizes the crankcase
and the gases exit through the valve cover port or the road tube depending on
the pressure differential.
Bill Lawrence
> Date: Sun, 26 Jun 2011 14:03:14 +0000
> From: bspidell@comcast.net
> To: austin.healey@gmail.com
> CC: healeys@autox.team.net
> Subject: Re: [Healeys] Question
>
> That was our first thought, too. But the head was rebuilt by an extremely
meticulous mechanic (a New Zealander living in Modesto, CA) so although it's
possible it's not probable.
>
> Trying to figure out if/how installing a rear main seal could cause this.
>
> Bob
>
> --------------------------------
> Bob Spidell - San Jose, CA
>
> ----- Original Message -----
>
>
> Worn valve guides??
>
> Sent from my iPhone
>
> On 26/06/2011, at 12:58 PM, Bob Spidell <bspidell@comcast.net> wrote:
>
> > After bragging about our 100M's compression numbers I have a
> > concern. We seem to be getting a lot of pulsed pressure in the valve
> > cover, as felt at the oil filler hole. There is very little pressure
> > at the end of the road draft tube. Given we have good compression,
> > so, theoretically shouldn't have a lot of blow-by, what could cause
> > pressure in the valve cover? The engine was totally rebuilt, and I
> > believe we cleaned out the road draft tube but don't remember for
> > sure (we were otherwise pretty careful).
> >
> > All hints, ideas, even knowledge welcome.
> >
> > TIA,
> > Bob
> >
> > --------------------------------
> > Bob Spidell - San Jose, CA
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