Hi,
I am converting from 1600 single port 1600 to twin port and have bought the twin port fan housing. As this does not have flaps ( internal flow veins apparently) how does it operate. Do I need the thermostat- if so what does it hook up to

Thanks

If it's an OG fan housing it will / should have flaps.

If it's aftermarket crap, it won't have the holes to mount flaps, or the directional veins inside.

If you have an aftermarket shroud you may not have all the correct fins inside it either, depending on which one you’ve bought.

Best option is to try and buy an original one with the flaps.

Second best option if you think you’ve got all the correct fins inside yours is to transpose a set of original flaps and linkage bar into your fan housing. I did this for a 36hp shroud because they never came with flaps.

There’s a bit of complexity here because if you had an early 36hp shroud that never had flaps then it would cool effectively without them and the flaps just help it heat up to temperature quicker and therefore prolong the life of your engine. However you have a later shroud that was designed to have flaps so the flaps are needed to correctly divert the airflow evenly over all the cylinders. So even if you didn’t have a thermostat and just left your flaps open the whole time, you would still need the flaps!

Hope that helps


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Hi,
It's an aftermarket from vwcoolair.
https://www.coolairvw.co.uk/Item/Shop_b ... k-CB-.html

I,ll check it out when it arrives. I know it doesent have the flaps coz I asked about this before I bought it. "It comes with is own channels inside to flow the aura"
it still has to operate through the thermostat though-'or,it is cooling all the time ? I,ll give them a bell and see if they have fitting instructions. They must sell loads of these.

If all else fails yes I can adapt the flaps to fit somehow.

Thanks

lol.... fitting instructions....

You'd have to drill the holes in the correct places to mount the flaps inside, and without a stock fan housing to copy then that'll be a bit of a guess. As always, well nearly always, best to fit OG tinware.

Definitely go OG - aftermarket may be nice and shiny, but it doesn’t help your engine.

If you want a shroud with heat exchanger outlets then there’s no reason to get a 36hp style because all types of oil cooling and both single and twin port engines were made with heat exchanger outlets so you can get an original shroud instead.

Even though they say it has the correct fins inside they rarely do - only CB aftermarket shrouds are made close enough to work well. More importantly no 36hp shroud ever had heater outlets so the airflow doesn’t work properly in them - if you look they are just square cut into the front face whereas original shrouds the heater outlets sweep out and the fins inside are designed to use them as part of the overall cooling effectiveness.


This website has everything you need to know about fan shrouds and cooling:

http://www.vw-resource.com/cooling_system.html

http://www.vw-resource.com/vanes_thermostat.html


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Hi ther, that's a great website, many thanks.
My single port 1600 has the old. NOn doghouse fan with thermostat and flaps.,ran ok. Went for a top end rebuild when it spat a couple of plugs so went for a 1600 twin port. Would the old fan housing be enough? After all the only significant change is single port to twin port. Still running a single centre remount carb.

Thanks

Have you mocked up the thermostat system yet?

I thought SP and TP engines had different rods through the head? But that might be 1200 different to 1600. Can't remember where the change was

Not yet, getting to that on Saturday. There's a twin port dog house housing on eBay will clean up. no flaps . Will my flap mechanism fit onto this. (I have the non doghouse single port housing)

Thanks

Yes regarding the flaps, but not the cross bar.

Pretty sure the flaps will transpose across but you’ll need a different linkage bar as it needs to go round the doghouse. There’s a bar for each set of flaps and a third one to link them, as opposed to the single bar you have for a single port shroud.

You’ll need to pick up the mount which transposes the oil cooler too and a ‘Hoover bit’ (named after Bob Hoover, nothing to do with suction) which makes sure the airflow goes through the oil cooler and not around the edge.

I presume the doghouse cooler you’ve found comes with the two bits at the back too. And you’ll also need a set of twinport tinwear which has space for the manifold and also has a hole in the rear piece for the exit shute. Not sure if you can get away with just the head tins and rear piece or if you’ll need everything.


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Non-doughouse first:



Doghouse second:



You can see the Hoover bit in the second photo too.

Bit more light reading about fan shrouds if you fancy it too: https://www.thesamba.com/vw/forum/viewt ... p?t=492074



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Thanks both that's top info.

I think I have the gist of it now. I,m dumping the new set and on the hunt for a doghouse set up. Trusted and true

Cheers

Here’s a very good website to have a browse through. The video links on installing the tinware are very cool in an 80’s mullet kind of way. http://awesomepowdercoat.com

Ideal fan shroud is a trekker one. They’re rare, although Awesome will do you a fully refurbed one at a cost.

Another very handy website is this one if you want to learn more about airflow. http://www.volksbolts.com/faq/cooling.htm

As important as the shroud are the cylinder tins. Make sure you have OG with the internal deflectors. These push the air towards cylinders 1 & 3. 3 can suffer a lot as the shroud is offset.

If you’re not running heat exchangers get some of Butty’s heat shields https://www.buttysbits.com/product/bb-1 ... g-j-tubes/

Finally, if you want your tins powder coating give Birkenhead Powder Coating a bell. They’ll do it all for you.

Good luck and happy research !

Jonny