[tcb] Re: Speaking of Valves
- From: "w.wood" <evil.scientist.boo@xxxxxxxxx>
- To: tcb@xxxxxxxxxxxxx
- Date: Tue, 26 Jan 2010 07:40:02 -0500
Most of the big dollar VW race setups now are using vacuum pumps as well.
There's obviously enough power to be made to overcome the power drain on
using the pump. But yes, venting the valve covers and a good breather box
are definitely good things to have.
On Mon, Jan 25, 2010 at 11:39 PM, Gerald Livingston <
gerald.tcb@xxxxxxxxxxxxx> wrote:
> Add an airbox. Popular with racers with higher than normal case
> pressure at high revs.
>
> Add a nipple high on the valve cover and pipe (hose) it up to a
> breather box that gets hooked to your air cleaner.
>
> Just for an idea go poke around the Gene Berg catalog. They sell stock
> valve covers with vent nipples added and also sell breather box setups.
>
> G2
>
> On Mon, 25 Jan 2010 19:15:00 -0800 (PST)
> atx <atx_bus@xxxxxxxxx> wrote:
>
> > Good stuff. How do you vent the covers?
> >
> >
> >
> > Jeff
> >
> > sent via iPhone
> >
> >
> > On Jan 25, 2010, at 9:02 PM, "w.wood" <evil.scientist.boo@xxxxxxxxx>
> > wrote:
> >
> > it's heat and pressure related. even when an engine has very little
> > leakdown (piston rings, valve guides etc.) there's still a lot of
> > pressure that builds up in the crankcase. In a stock ACVW the 3/4
> > side also get a lot of oil slosh (windage) into the valvetrain area
> > which further causes some pull when it drains back in. This means
> > that the air inside those covers is also less dense than the air
> > outside the valve covers. all it takes is enough pressure
> > differential and heat and you'll pull a gasket.
> >
> > I used to think it was just bad gaskets or warped covers but venting
> > those same covers and alleviating the crankcase pressure helps solve
> > the problem. If you don't want to vent the covers then a little
> > permatex works wonders. Just be prepared to do a little scraping
> > between gasket changes.
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > On Mon, Jan 25, 2010 at 12:49 PM, sammie smith
> > <bugcollections@xxxxxxxxxxxxx> wrote: Here is a good tech question
> > for you Will or any other ingenious VW engineer/mechanics that want
> > to chime in. What causes the valve cover gaskets to "suck" in, i.e.,
> > sometimes work loose on the bottom and move up into the rocker
> > chamber, which of course causes tremendous oil leakage. Happened to
> > a VW mechanic friend of mine a while back on his daughters car and
> > she ran it out of oil with all of the resulting burned up engine
> > problems. Valve cover gasket had "sucked" resulting in loosing all
> > of the oil in the engine. I know how to prevent it: have talked
> > about that before; but what causes it. Got into an academic
> > discussion with another VW mechanic friend about how is it possible
> > to "suck" a valve cover gasket. Normally there is positive crankcase
> > pressure and the pressure through the push rod tubes should keep a
> > positive pressure inside the valve cover/rocker assembly resulting in
> > the pressure to attempt to "push" the valve cover gasket outwards,
> > which of course it can't do because of the lip around the valve
> > cover. Have talked to one old VW dirt track racer who ran big
> > stroker motors on the dirt tracks where there was a lot of
> > acceleration/deceleration of the engine and it he says it was a
> > common problem which they usually cured by welding some tabs around
> > the inner side of the gasket channel. Have had it happen to me and
> > it is a rather common occurence in the VW engine. But what causes
> > it? For the engine to "suck" a valve cover gasket there has got to
> > be at least some time when there is a negative pressure (vacuum) in
> > that chamber. With my knowledge of the flat-four, 4-cycle engine, I
> > don't know how that is possible. The only thing I have been able to
> > deduce is that it might be possible under extreme engine deceleration
> > for the piston on the down-side compression stroke (since it has no
> > positive pressure on that stroke under deceleration) to have a vacuum
> > so severe that it sucks pressure through the valve guides and creates
> > a vacuum in the valve cover chamber. But I don't really think that
> > is possible. Comments?
> >
> >
> >
>
>
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