<VV> LM turbos and no lower shrouds

[Mark Durham]

Eric and all; it is true that the stock systems were designed to
provide reasonable temp, but there are two sets of baffles/shrouds that
are worthy of note here, and they both have different functions.
First, the shrouds that box in the front and back portions of the
engine, the design of the heads, the turkey roaster and the inner
cylinder baffles direct the airflow to keep the engine cool. The bottom
shrouds inhibit that flow when temps are below a certain value so the
engine temps stay in a determined range so heat is available and so
engine temps are more consistent. This extends engine life because it
keeps temp in design limits.
Turbos do raise the temps and turbo engines, in airplanes and cars, air
cooled ones, have a shorter life span, or in my mechanic lingo, shorter
TBO, time between overhauls.
I found my em 62 with a 270 cam and stroked to a 64 110 runs smoother
and cooler and hot starts better when I have the lower shrouds off in
the 90 plus temps we get in the summer when I Don't need heat. Mark
Durham

Sent from my Windows Phone From: Eric S. Eberhard
Sent: Saturday, October 22, 2011 11:30 PM
To: virtualvairs at corvair.org
Subject: <VV> LM turbos and no lower shrouds


I am always puzzled by this discussion which comes up every so
often.  The car was designed well from the factory.  If you have
everything correct -- all the shrouds as well as seals and so forth,
there is no better system.  I am in AZ, totally bone-stock, at
altitude (3500-8000 feet), summer temps of 110 ... and I NEVER have
even gotten remotely close to overheating.  Our speed limit is 75 and
I can go up a 6% grade at 80, no over heating.  From my 3500 to 7500
feet happens in 6 miles, no overheat even at 80.

I believe that those that overheat and think they need to
remove/modify shrouds simply have other problem they are compensating
for.  Mine is a 62 EM and perhaps it is different, but I have had to
EM turbos as well and neither ever had a heating problem.
And we get 20 degrees in the winter, so having those shrouds on then
is crucial and I don't need the hassle of swapping them on and off.

One writer pointed out the correct heat is required for quick
boost.  Correct.  Some people even wrap their exhaust to push temp
even higher, for that reason.  Some people mistakenly use a "free
flowing" muffler which actually reduces boost and is bad.  I used an
NOS turbo muffler.

Keep it stock and it will be absolutely reliable (my only mods are
electronic ignition and related upgrades).

If you have heating problems -- are your plugs too hot?  I use Nology
Silverstone plugs and they perform very well with a 38 gap and hot
ignition, no overheating.  They are made for vintage cars.  They are
expensive, but I have over 30k on them and they are clean as a whistle.

BTW -- opinions are like belly buttons and so I have one.  I respect
others, as other people have done neat things.  I am not a good
enough amateur mechanic to re-engineer things.  But I believe a
properly set up stock system -- not all that hard to achieve -- is
going to be reliable.  Doing the ignition and putting a Judson on one
of my cars is sort of the limit of my explorations.  However, my
Spyder always has instant boost (no lag), boosts at 2000 rpm in 4th,
pulls to redline, and I can't overheat it.

So if you are in the mood, you might try making it factory spec
first, seeing how that goes, and then modify.  Otherwise, you might
mask a problem that later gets ugly.

Eric

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