Fresh air delete/181 shroud clone done the right way

[AlteWagen]

Cant afford the $300+ price tag of a 1973 only thing shroud? I know I cant so I made a better than 181 shroud.

Im tired of hacks just cutting off the ducts, welding up the holes and selling a "cal look" or home made thing shroud. If the internal directional veins are not removed the air flow inside the shroud can cause problems with turbulence resulting in inefficient cooling. Using the plugs on the ducts also causes the same problem. The Raby trick of leaving the veins but drilling a large hole to simulate the "bleed off" the stock heater boxes is one way to do it, but I would rather show the correct way of doing the modification.

I used an early FI shroud with the velocity ring and large negative slot but the same will work on any of the DH shrouds that you can get for $20 at the swap meet.

In these pics I circled the spot welds that need to be drilled out in order to remove the two internal veins that direct air to the heater system.

this is the tricky one

After the welds are drilled out the easiest way to remove the ducts is to give them a squeeze with some channel lock pliers.

Once the top one is out the bottom one will just slide out

Once all the veins are removed, dolly the remaining metal and make your patch panel and weld it up.

Here is a pic of all the parts that need to be removed for best results

It took me a few hours from start to finish just to do the removal and welding, add a few more for bodywork and paint.

I use rustoleum semi gloss engine enamel, its close to stock and holds up to gas and oil spills well.

Happy chopping!!!

[swervyjoe]

Very nice. I'm fixing to do this. I had a basic idea of how to do it, but its nice to see the pics ahead of time.

[EverettB]

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[Bruce]

[AlteWagen]

I have a perfect set of flaps with linkage and tstat that will be used for this shroud. The ones on the shroud in the pics were $1 bin specials I used for mock up.

[rrcade]

I have a Doghouse shroud now with the round caps on the heat ducts, so is this procedure the same for any doghouse shroud? How much additional cooling will the heads/cylinders really see?

[rrcade]

Also, I've read about cutting off the ducts, patching the holes and then directly behind the ducts you patched you're supposed to cut a inch and a half hole in the backside of the shroud? How is that any different than just not capping your ducts on the front? You're still wasting air that could be used for cooling right?

[yellow73kubel]

[APPLEGREENVW]

[AlteWagen]

Im still using the short puma/brazilia non fresh air shrouds with venturi ring as they seem to work best for my applications. They do not have any diverter veins like the thing shroud which is why I removed them in the 181 clone mod. I would rather use all the cooling air directed to the heads than to drill a huge hole to "normalize" or reduce turbulence in the shroud.
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[APPLEGREENVW]

[Motor60]

Anyone??

[bugguy1967]

The engine won't overheat if you just delete the arms; it's just a good idea to give the air somewhere to go, to reduce turbulence issues. We run some f'd-up shrouds without major issues. Doesn't make it right, just saying we can get away with a lot. I hole saw out a 1 1/2" hole on the frontside too, but recently saw a guy just pull out the channels instead of making the hole. Was way cleaner. I think that's how Thing shrouds are internally; they are without the heater channel. There's just a few spot welds that hold them in place. Drill, and they can be pulled out.

Here's an engine that I just sent on it's way: O.E. doghouse shroud, modded to look like a Thing shroud. It has 1 1/2" holes in the front side. I used matching .030" sheet metal, got it spot-welded in, and used a thin layer of fiberglass resin to mask any imperfections. I got the rounded corners just right.

[esde]

Hell, if you are getting rid of the fresh air outlets, why even keep the "hips" ?
They just get in the way of nice things like injectors, so I removed them completely, including some of the internal vanes. Engine runs nice and cool

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[bugguy1967]

For nostalgia, duuuuuh.... lol!

[AlteWagen]

I added this info on the upright shroud thread and thought it was an interesting read

http://www.volksbolts.com/faq/cooling.htm

http://www.thesamba.com/vw/forum/viewtopic.php?t=492074


For me the fact that the early non fresh air large shroud was described as "Modified shape increased cooling air throughput" in Progressive Refinements using the same fan as before leads me to believe the shape of the shroud is important. When the heater system went fresh air the heater boxes had to have constant air to control heat even when not in use which dumped the cooling air via the bleeder valve on the top of the box. This bleeder valve is the reason for the 1.5 in hole mod Raby suggested when leaving the veins in place

Im wondering that even though the hole in the heater box measures the 1.5 in does the flap and flap housing cover cause a restriction allowing pressure build up to keep the majority of cooling air directed to the heads and cooler? To me it seems that a 1.5 in hole in the front of the shroud is just bleeding off too much air for my liking.



For the record every 181 shroud Ive seen with the exception of 1 had the heater diverter veins in place. That 1 shroud also had the positive cooler scoop while the others were mixed pos and neg. I still am unable to pin down every application of the 181 shroud. Im guessing that export/domestic/mexican varied through out the years.



Of all the testing Ive done (Factory DH with neg and pos slot, EMPI 36hp large pos slot, Puma neg slot, Brazilia working FA heat) the ring, flaps and 356 pulley gave the best results. All tests were performed on the same engine in my daily driver bus with factory finger, sled and industrial tins in place (when not using heater boxes) and german head tins with spark plug cooling veins.

-Factory DH and Brazilia with working heat ran the highest CHT (40* above no heater system)

-Positive slot lowered OT 10* compared to negative slot (did not monitor #1 CHT to see if cooling was compromised as mentioned by Raby)

-Venturi ring lowered CHT 30* and oil temp 10*

-Flaps to puma shroud (no t stat just spring keeping flaps open) hastened CHT cooling when not under load.

-356 alt pulley lowered CHT 30* and OT 10


The next test before I take the engine down for another inspection/rebuild (now at 160K miles) will be a late FI shroud rear section with internals with a non FA 40hp cover. It will have small slot which I have not tried before so I can see how OT and CHT temps are affected and to compare to the EMPI 36hp shroud.

These are the only pics I have but the shroud has been cleaned, welded and painted and ready to go in as soon as the baby gives me enough time to do it.

I may also test a positive scoop on the peanut slot and a half positive scoop on the large negative shroud as I now have 4 CHT gauges to help collect cooling data. I would love to test the Type 4 cooler mod with the 3 different slot types. Im thinking the positive slot is needed to take advantage of the greater area of the cooler vs the peanut slot which reduced air to the oil cooler to give more cooling to the heads.
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[dsrtfox]

On your custom shroud are you using the later, wider fan?

[neil68]

[Glenn]

I'd love to get one of these and see how it compares to a real Type 181 shroud. But i'm "old school" and like using genuine OE parts like back in the day.

http://usstore.concept1.ca/Fan-Shroud-W-OHeat-W-Holes-COOLED.1.2-62217/

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