Fan shroud flaps

[Glenn]

[EVfun]

[wcfvw69]

[oprn]

vwracerdave, I see by your signature what you use your VWs for. That's cool and no you don't need temperature control on the drag strip. In fact you really don't need the fan and top tins either. Back in the '70's when I was following the VW drag scene in the magazines there were a number of fellows who ran the 1/4 mile without fans, tins and even generators. Just a set of Webers, an extractor and a magneto. Some even push started to save the weight of a battery and starter.

Darrell Vitton(spelling could be wrong)was one of them. He ran a VW powered Fiat at that time. I hear he competes in vintage now.

[wythac]

Most people don't have a complete set to run, or care to go to the trouble to find all the parts, therefore tend not to have them on their engines. I feel this is the primary reason so few use them on builds, not whether or not they find them necessary. Once deleted, the question of whether they are necessary is an exercise of conversational reverse engineering.. I've always used them and feel I have increased the longevity of my engine builds as a result. But I live up north.


Chopperimpala, Most (all?) aftermarket shrouds aren't drilled for them. The flap housings have threaded dropouts, so all you really have to do is drill some holes in the shroud for mounting screws to go thru. Your cylinder tin will need to be slotted for the shroud to fit over them with the flaps.

In order to determine locations for them, you'll need the crossbar that ties the two flap assemblies together. I think there are two different ones, for doghouse and non doghouse shrouds.

Mount the t-stat, housing, and actuator rod on your engine first. Rod goes between the combustion chambers on the head in an obvious wide galley. Since that rod moves the flaps above it, the alignment of that passenger side flap in the fan shroud is key.

Once that side is done, use the crossbar to determine spacing for where the second set of flaps should be in relation to the first.

Do yourself a huge favor and don't have anything mounted on your shroud, you are going to have it on and off of your engine dozens of times and won't want the extra weight. Its optimal to have the engine at bench height for this work as well.


EDIT: Forgot to mention that each side has its own distinct flap assembly, beware that you get a right and a left when buying them. Right hand side flaps have a small fabricated receptacle for the actuator rod that goes between the t-stat and the flaps on that side.

PM me if you have questions, I may be able to help. Good luck with your project.

[wcfvw69]

I think two things are really overlooked when it comes to having these thermostat and shroud flaps on a stock engine-

1) The car's heater works SSOO much better and the air coming out gets hotter much faster.

2) Cold engine driveability.

I bought my 67 in Los Angeles where it lived it's life. Of course the engine was missing the thermostat, flaps, etc. The warm air hoses were not hooked up to the oil bath and it was missing the pipes at the heads to hook them to. The engine was a cold blooded pig until after about 7 minutes of driving. The heater never got really hot and took a long time.
After installing those missing items, the engine runs perfectly and drives perfectly first thing in the am. Start it up and drive off. The heater will bake you now and it does it fast.

The good news is these parts are plentiful out there in good used condition. So many were removed that we'll never run out. Many people sell complete sets in the classifieds on this site.
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[Wetstuff]

Guys, To those of us who have not taken the engine apart—how do you tell if you have the system, or not? (looking from the outside of an intact engine) Thanks.

Jim
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Manx #2614

[wythac]

Look between the passenger side sled tins and the pushrod tubes on the RH side and you should see a ribbed cylindrical object. That's the thermostat. See if it has a small rod protruding from its top into the head.

From the rear of the car you should see two machine screws going into the shroud on each lower outside corner, just above the cylinder tin. These would be the two rear mounting screws for the flap assemblies, with two more around the front on each side, 4 each, 8 total.

And, if you reach around by the cooling fan inlet you should feel a 20" long metal bar going across the motor behind the fan that connects the two flap assemblies over each cylinder bank.

You may have just some of the hardware...its likely not functional if you are missing a piece.

[Glenn]

[drumbum68]

[oprn]

[drumbum68]

Uhmm. Windchill factor has nothing to do with an engine.

[chrisflstf]

Flaps may be good for preheating the motor, but not good when they stick shut and you fry the motor

[Glenn]

[wcfvw69]

[wythac]

Possible, yes, but in over forty years of being around these engines and around all the people that drove the cars that used them, I've not heard of one failure attributed to the thermostat system getting stuck in the closed position.

[oprn]

[Ken]

Boy, a simple question sure ruffled a lot of feathers!!

As far as windchill factor, as I see it, if it's 30 degrees out and a fan is blowing that 30 degree air fast across the cylinder fins, I'm pretty sure that air that's moving is colder than the ambient "non moving" air is?

Then again I'm just a dumb car guy wanting my daughter and I to be warm during the early spring and fall months in the PNW, so what do I know?

[wythac]

I'll stop this line of contention before it gets going. Windchill is most commonly used to measure the perception of temperature on skin...the quicker heat is whisked away from the surface of your skin, the colder it makes you feel, so 30F with a 0 mph wind feels warmer than 30F blowing across your skin at 30mph. This is because heat generated by your body warms a thin layer of air next to it...the more the wind blows, the quicker this layer is removed, and the colder you feel.

However, the same principles apply for blowing air across a heated surface like your cylinders and heads...if there was no difference in the cooling ability of air at 0mph than the speed at which your fan can blow air across your engine's cooling surfaces, there would be no need for the fan, because it would make no difference in the temp of your engine surfaces.

Both processes involve the movement of air over a surface and the difference between the temp of the air and the temp of the surface, creating a dynamic environment where heat is exchanged. The increase in the speed at which air flows over a surface effects an increase in the rate at which the temperature of that surface will change.

[oprn]

Exactly right!

The term "wind chill" is not normally associated with inanimate objects but the principle is the same. As long as there is no source of heat, there is no loss of heat therefore no wind chill.

Those of us from the frozen north are pretty familiar with this transfer of heat caused by moving air. At -30 you plug the block heater in to be able to start your car in the morning and there is a world of difference between plugged in parked in the car port or plugged in in the open yard when the wind blew all night!