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Lower shroud cooling slots?
Posted by: bobvair ()
Date: February 11, 2021 11:52AM

Decades ago I saw a nifty mod to the lower shrouds for additional cooling but cannot locate a description/photo/diagram.
A slot cut into the shroud bottom with a slight flange on both sides to capture a metal closing strip. On hot days the strip could be temporarily removed for additional hot air exhaust.

Anyone old like me recall this mod and perhaps have instructions for the mod?

My thanks

Bob Slusher

Portland, Oregon

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Re: Lower shroud cooling slots?
Posted by: RobertC ()
Date: February 11, 2021 12:26PM

Over thinking.

You do not think GM tested for hours the Corvair in the desert outside Phoenix?

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Re: Lower shroud cooling slots?
Posted by: bobvair ()
Date: February 11, 2021 12:44PM

Friend in HOT southern Oregon needs a tad bit more cooling on his summer romps. Rather than removing the lower shrouds I thought this mod would be easy for him.

Bob Slusher

Portland, Oregon

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Re: Lower shroud cooling slots?
Posted by: RobertC ()
Date: February 11, 2021 12:56PM

bobvair Wrote:
-------------------------------------------------------
> Friend in HOT southern Oregon needs a tad bit more cooling on his summer romps. Rather than removing the lower shrouds I thought this mod would be easy for him.

Could the higher temp of his engine be from running too lean?

I made carb changes decades ago (on a 140 Corsa) and the head temp went up 50 degrees (freeway cruise in a temperate area).

Increased the jets and the head temp dropped back down to the previous normal.

But, you (he) can make any changes you want.

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Re: Lower shroud cooling slots?
Posted by: steve c goodman ()
Date: February 11, 2021 01:00PM

Hi Bob: The only time I saw the mod was customer who moved here from northern Calif where temps vary. He sacrificed 2 sets of shrouds to make his. A bit smaller cutout in each side under exhaust manifolds and then a larger/overlap but same shape from the other pair with sheet metal screws through both to hold cover in place or ease of removal. Obviously the inner edge of the mounted tin needs to stay in place due to thermostat mounting.

When he got here he discovered having water leaks at the cutout places would steam his windshield in winter when water hit the hot exhaust and defroster on.

best wishes, Steve
Rear Engine Spec. Inc. Golden, Colo.

1962 spyder 3.0L turbo---1965 Crown V8
1967 monza 110/4---1968 monza 110/4
1971 amante gt 110/4
CORSA/RMC/PPCC/V8 Registry

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Re: Lower shroud cooling slots?
Posted by: jamesolefjensen ()
Date: February 11, 2021 01:03PM

I like the idea. Perhaps louvers would work. A sheet metal shop might be able to do the punch work.

I agree that GM tested the snot out of these cars and that they determined quite scientifically that the cooling was sufficient for hots days in Arizona.

But they also tested the heater design in Minnesota, for God's sake. I'd bet the happy medium was more than a little biased towards cold environments. I'm sure they figured cooked oil was better than frozen passengers.

James
65 Corsa
SF Bay Area

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Re: Lower shroud cooling slots?
Posted by: bobvair ()
Date: February 11, 2021 01:21PM

His fresh turbo motor does have a stock jet/rod which to my thinking is a tad on the lean side. A recommendation to him would be to fatten it up. The motor clearly overheated which left him on the side of the road last August.

Good advice from Steve about the steam room interior during wet weather. Very wise. My thanks to all.

Bob Slusher

Portland, Oregon

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Re: Lower shroud cooling slots?
Posted by: PGVair ()
Date: February 11, 2021 03:29PM

I saw an Ultravan at the 1980 CORSA Convention that had hinged flaps that could be opened and closed with a cable or cables from the dashboard. The flaps opened up about a 2" - 3" wide area on the bottom of the shrouds, running front to rear, so they opened sideways. I don't recall if they still had the thermostats; the thermostat brackets would have been in the way, so the thermostats may have been removed.

The best thing I ever did for cooling was de-flashing the heads. Based on the stock cylinder head temperature gauge, I estimate the head temperature was reduced about a 40 - 50 deg.

Wade

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Re: Lower shroud cooling slots?
Posted by: 63turbo ()
Date: February 11, 2021 05:55PM

One of the other ways I've heard of to accomplish the same thing is to put holes in the lower shrouds, and for cooler weather operation, put a block off plate on.
There is a fairly large drop in head temperatures when removing the lower shrouds vs having them on. Turbos and 140's are the ones that see this done, at least when it is hot enough. One fairly controlled test that I've read about at Bryans Autcross page done by Bruce Shrug with a stock 140... 80 degrees outdoor air temperature, 80 miles an hour, lower shrouds on, head temp = 380, lower shrouds off, head temps = 300.

------------------------------------

Kevin Nash
Friday Harbor Washington
63 Spyder, Daily driver, EFI read about my project here: [corvaircenter.com]
first test start on EFI here:[www.youtube.com]
first official EFI boost test here:[www.youtube.com]
My new fan! [corvaircenter.com]
engine less 62 Spyder
Canadian 64 Monza Parts car



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Re: Lower shroud cooling slots?
Posted by: Frank DuVal ()
Date: February 11, 2021 06:13PM

I just take the lower shrouds off and put them back on for cooler weather when I need defrost. No need to jack up the car, you can reach all the hardware. It was common for 110 PG engines to ping when it shifted to high gear around here on the 80s gasoline.

Of course, that was me years ago, I haven't removed a lower shroud for seasonal changes in 10 years.....winking smiley Maybe because I have 95 HP engines.

I just pull the hinge pin, and remove the damper door still attached to the assembly, as trying to remove and reinstall the "Jesus Clip" is way too much trouble.grinning smiley

Frank DuVal

Fredericksburg, VA

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Re: Lower shroud cooling slots?
Posted by: irfgt ()
Date: February 15, 2021 01:53PM

If your car overheats with stock shrouds and properly operating thermostats the problem is not the shrouds. Modifying the shrouds is just masking over another problem. Look elsewhere.

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Re: Lower shroud cooling slots?
Posted by: RexJohnson ()
Date: February 20, 2021 09:47AM

To add extra cooling for pulling my trailer in the summer I took an early set of lower shrouds that have the thermostat towards the front of the car. These were used up till '63 I believe. I then cut out the bottom behind the T stat and left the sides complete. This opened up about 2/3 of the bottom. The T stats stayed hooked up so the doors didn't flop around and with the front part still intact the car still had great heat when needed. For winter driving I would switch back to the full shrouds.

RJ tools
Salem,Oregon

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