<VV> LM turbos and no lower shrouds

Sun Oct 23 11:11:33 EDT 2011

Hello from Germany,

your discussion sound interesting. I do own a Porsche 964 - with no eat problems, a Spit Window VW bus - with the same heat problems as the Vair and a 66 Corsa Turbo. I would like to see some pictures of your modifications if possible. Thanks.

Regards from f... cold Bavaria
Ulli

Am 23.10.2011 um 13:51 schrieb jvhroberts at aol.com:

> 
> Given the amount of air that blows out of the bottom of the engine, I wouldn't worry too much about stuff flying up there. After all, what's exposed is actually more robust than the shrouds! They aren't there to protect anything, they are there to keep the air under control. Or so we thought... <G>
> 
> My experience with no shrouds was wonderful! Warm up is still reasonably quick. I cut back the shrouds because the heater was suffering, and my thinking was, by retaining a short section near the front of the engine, it would capture more air for the heater. And it did, with no obvious change in CHT. Also, I got a lot less steaming of the windshield when I drove through a puddle with the heater on. 
> 
> Remember, 911s don't have any lower shrouds, and they also warm up quickly. They also use shrouds on the exhaust system for heat, not engine heat. 
> 
> 
> 
> John Roberts
> 
> 
> 
> 
> -----Original Message-----
> From: Carlton Smith <carlton55 at comcast.net>
> To: 'Eric S. Eberhard' <flash at vicsmba.com>; virtualvairs <virtualvairs at corvair.org>
> Sent: Sun, Oct 23, 2011 7:02 am
> Subject: Re: <VV> LM turbos and no lower shrouds
> 
> 
> Hi Eric,
> 
> Thanks for your opinion. I am seeking those with experience and you have
> shared yours.
> 
> I have owned my particular 1965 turbo Corsa since 2007. The previous owner
> had rebuilt the engine in 2000. It was totally stock with the exception of a
> Clark's 260 cam. On the highway in the Midwest if I went over 65MPH for any
> length of time  on a 75-80 degree day the head temp would reach 425-450
> degrees (the gage is accurate as I have a infrared temp gun). The engine
> always had a couple of (loud) clacky valves that were lifter/cam oriented. I
> decided to have the engine rebuilt last winter by a professional Corvair
> mechanic. The engine was totally rebuilt stock, head veins cleared as much
> as possible, correct valve geometry restored, etc. We discovered the bad
> Clarks cam grind on 2 lobes is what was causing the 2 clacky valves and
> replaced it with an Isky cam of the same 260 spec. (I checked with others
> and found they also had problems (on occasion) with this particular Clarks
> cam). Anyway I now have normal quiet engine now. However, with the shrouds
> on I still would go to 425-450 degrees on long distance highway traveling.
> So I decided to try the shrouds off option and it usually travels at 300-325
> degrees and on a hot day might go to 350. I am told by may turbo owners and
> the folks at Clarks that the shrouds on temperatures are absolutely normal
> for a turbo. Also that those temperatures will eventually shorten the life
> of the engine as compared to a standard engine. I drive the car every day in
> the summer and garage it in the winter. I drive it as long as I can every
> year so that does involve fall and spring days in the upper 30s and 40s. I
> can still get heat in the cab from the upper shroud hose so that is ok with
> me. However, I don't like having the bottom of the engine exposed all of the
> time to possible road debris (rocks, etc.). I am a little worried about the
> start up/warm up factor although it seems it warms up fairly quickly. So you
> can see I am already at the point of making a possible mod decision. I am
> interested to know what John Roberts is suggesting.
> 
> Thanks for your input Eric!
> 
> Regards, 
> Carlton Smith      
> 
> 
> 
> -----Original Message-----
> From: virtualvairs-bounces at corvair.org
> [mailto:virtualvairs-bounces at corvair.org] On Behalf Of Eric S. Eberhard
> Sent: Sunday, October 23, 2011 2:29 AM
> 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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