topnotch at nycap.rr.com
Fri Dec 9 20:17:29 PST 2011
I don't think the valve swallowing problem was really heat related, they
broke when the guides wore enough to have them bending back and forth, I
suppose when they were really hot that would be the final straw...
I can say that at 12K feet and stock T3 injection the car would be gutless
but cool oil temps at low RPM even if lugged but if you upshifted for more
HP and higher RPM the Oil temps would ROCKET upwards....
Top Notch Restorations
topnotch at nycap.rr.com
71 Squareback "Hothe"
65 Notchback "El Baja Rojo"
65 Squareback "Eggcrate"
87 golf "Winterat"
93 RX7 "Redstur"
From: type3-vwtype3.org-bounces at lists.vwtype3.org
[mailto:type3-vwtype3.org-bounces at lists.vwtype3.org] On Behalf Of Jim Adney
Sent: Friday, December 09, 2011 10:17 PM
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
Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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