No thermostat and no vents flaps

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Aug 21, 2019
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Hi our bay has both. The trekker has neither, the dog house has the air block offs as does not use the heat exchanger. Both engines are 1641 twin port

What are the pros and cons to having no vents flaps and no thermostat?
Or would you source getting them and fitting them?
So, the thermostat and vents allow the engine to warm up when its cold, blocking air to the barrels/heads until the stat expands and the flaps open, allowing air to pass over the heads and barrels, as I suspect you already know.
Personally, I kept them all in our buggy engine, mainly because at the time (early 90's) I thought it was necessary, however, the tinware for the bus engine i'm putting in, i've deleted the lot. My thinking is that they were originally fitted to allow the engine to come up to temp in the winter, my bus wont see winter use, not proper cold use anyway, so I left them out. That and hearing that the 'new' thermostats fail in the closed position, allowing no air flow at all, made me think this is also the better option for an occasional use car.
Just my opinion, I'm sure their will be others that think they are extremely necassary.
The general argument is that VW would never have fitted them from factory if they hadn't been required.

The thermostat allows progressive cooling on start up so the engine warms up efficiently and doesn't get full bore cooling when its cold, so it prevents premature engine wear. The flaps direct the air so the hottest parts of the engine get priority cooling, and make the heating system most effective.

All that said, our VW's are now in general, low mileage hobby cars that are modified and subjected to fairly regular maintenance, so I think the effects mentioned above will be minimal. If you have the parts and they are in good order, then fit them and use them, but I really wouldn't worry about not having them.
Here in California it was common to remove the thermostat, flaps, levers, etc., as they were thought to either be unnecessary in our temperate climate or because folks were worried that the thermostat would fail (and that would fry the engine).

In essence, my Hippie forefathers were convinced that they knew more than multi-generational teams of German engineers.

My ‘71’s engine has no thermostat. The levers are long gone and the flaps are welded in the “open” position.

Now, (1.) it takes about 30 minutes to come up to proper operating temperature where it runs its best, and (2.) my heater never really heats, even though my mechanics have repeatedly assured me that everything is correct underneath (heat exchangers, insulated covers, cables et al).

I live in the desert now. For most of the year, a heater is not needed, but right now it is, damn it!
I managed to source some and fitted them last year when changing to twin webers.
As others have said they don’t fully open in colder weather, allowing the engine to be controlled at a nice operating temperature.

I noticed this on our last trip of the year last December and was slightly concerned because the flaps weren’t fully open after a long run, but then realised it was perhaps because of the fact it was Baltic outside.
The van ran a nice steady temp on the gauge throughout all of this and the dipstick was cool to the touch.

My basic understanding is that the flaps regulate the temperature rather than being either open or closed. I’m happy to have them 👍 mine’s a 1970 1641 S/P
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Basically if I can find some before engine goes back together get them and fit them, guessing there is s a size difference between twin and single port ones.
Basically if I can find some before engine goes back together get them and fit them, guessing there is s a size difference between twin and single port ones.
I’m not 100% sure about the flaps themselves being different, but the actuator bar at the back differs between single and twin because of the doghouse cooler.

Hopefully someone will post to clarify that.

Return springs are readily available, as are the retaining clips that secure the actuator bar at the back.

Thermostat and brackets are a bit hit and miss, but they do pop up on eBay. You’ll need the actuator rod too.

I ended up buying a couple of shrouds that had some but not all of parts, then cobbled it all together and sold the bare shrouds on.

They’re out there, it’s just finding them.

Here’s a pic from Bentley manual

Good luck 👍


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