[T3] T-4

[Dave Hall]

When I dropped a valve on my 1959 Beetle at 105,000 miles, it happened at a
leisurely pace on a flat piece of road in Norfolk (UK), which is pretty much
flat everywhere! 

Mind you the car was driven hard in town!

The main reason it happens is valve guide wear causing valves to hit the
seat at a slight angle.  After a while stretching the neck, or due to
corrosion on the weld area they break.  Ouch!

I overheat running up hills - makes me sweat like mad!  SUVs are similarly
overweight for the frontal area - no wonder they can't get enough air to
cool them!  

Dave
UK VW Type 3&4 Club
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-----Original Message-----
From: type3-vwtype3.org-bounces at lists.vwtype3.org
[mailto:type3-vwtype3.org-bounces at lists.vwtype3.org] On Behalf Of Jim Adney
Sent: 10 December 2011 03:17
To: type3 at vwtype3.org
Subject: Re: [T3] T-4

On 9 Dec 2011 at 16:55, ftalker at gmail.com wrote:

> Hi there
> > Less air means less cooling.

> This may seem to be true, but altitude also means that CR is 
> contiguously lower which means, (all tuning being accurate), that the 
> engine runs cooler.

Interesting thought, but to get the same power at altitude, one would first
open the throttle a bit more, that should bring the manifold pressure
(vacuum) and cylinder pressure back up to the same as it was at sea level.

Of course once the throttle is wide open, you've got no more head room and
you can no longer compensate, but up to that point I think power output
should be a wash and cooling should be more difficult.

This is where turbos really shine. They never run out of head room.

I've heard that air cooled cars don't seem to suffer from cooling problems
at altitude as much as water cooled. That info dates from ~1960, however,
before water cooled cars had pressurized cooling systems. I'd expect today's
cars with pressurized systems to work much better, but I don't know if
they're now better than air cooled.

I know that in 1968 I helped a family with a mid-60s microbus that had
swallowed a #3 exhaust valve. Oddly, that happened on a long decent, where
there should have been lots of cooling and almost no power output. VWs of
that era seemed to bleed a bit of gas into the mix even on downhill overrun,
so I always figured it must have been running lean and hot. However, I've
never been very satisfied with that explanation.

--
*******************************
Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
*******************************

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