<VV> LM turbos and no lower shrouds

Mark Durham 62vair at gmail.com
Mon Oct 24 19:24:26 EDT 2011

I must agree, I think GM did an excellent job with the engine, its
pretty much bullet proof. Even temps work in aircraft, in fact people
who pay attention to that get a lot more life out of their engines. GM
figured this out and used the shrouds to keep a even temp in uneven rpm
and power situations. I do not like that the oil cooler dumps into that
hot air, I think the engines would do even better if the oil cooler air
went out the back, maybe with its own thermostat for getting the oil to
temp, but other than that, its a good durable motor.
I do remember I compensated for a overly active fuel pump by removing
the lower shrouds. Got tired of flood starting it. It did better when
not so hot. But I put the shrouds back on after adding a pressure
regulator to the fuel circuit. And it was fine.
Mark Durham
Sent from my Windows Phone From: Eric S. Eberhard
Sent: Monday, October 24, 2011 2:43 PM
To: Mark Durham; virtualvairs at corvair.org
Subject: RE: <VV> LM turbos and no lower shrouds
I agreed all the way through the sentence ending with "design
limits"  :-)  I believe that more consistent temps with the correct
range are a desired end result and that just making it run colder and
inconsistently and harder to warm up ... not so good.  E

At 08:48 AM 10/23/2011, Mark Durham wrote:
>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
>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.
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Eric S. Eberhard
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