Removing SC heater Fan

[Guest]

As part of some modification to my 1982 911 SC I am trying to reduce
unnecessary weight. As part of this process I am looking
into removing the electrical heater fan located in the engine compartment
that boosts the air flow from the engine cooing fan to the heater.

If I remove this I would then intend to duct the outlet from the engine
cooling fan direct to the heat exchanger inlets on either side of the engine
compartment. To do this I need a 'manifold' that will bolt to the outlet
aperture of the engine cooling fan and provide two spigots to connect the
flexible pipes to the heat exchanger inlet pipes.

Does anyone know who might provide such a manifold.

If I decide to do away with the heating system all together, should the
outlet from the engine cooling fan be blocked completely.

 

[bones]

This is a relatively straightforward mod' Stuart, you can see most of what needs to be done in the engine pics on my car, there is a wealth of information on it at Pelican Parts and Rennlist. You should - if you still want heat - and want to make a 'correct' looking installation get the parts you need from a breaker and blast and powder coat them if they are looking a little tatty. I believe some but not all these parts are still available from Porsche too but I imagine they will cost you dear.
Basically you need the two ducts that sit either side of the fan and you will probably need some engine tin (I have early heat exchangers on my car so it was a little more complicated as the HE heater ducts are in a slightly different place cmpared to the stock system) then it's a case of removing the unwanted items and with a little judicious hammering of the near side tin to fit it round the dizzy and some new 10mm bolts from Porsche you are there. The ducting I got from Type 911 but use what you like. the ducts and tin I bought from Pro-9 (in the back of PP) for £20 all in, blasting and powder coating should be about £10-£20 as they will do such little items as part of someone elses larger job.
If you decide to dispense with the heat there seems to be three schools of thought on this. A couple of guys in the states who race have just removed the parts and left things as they are, apparently with no ill effects but I don't like the idea of all that spare heat going nowhere in particular and hanging around the engine. The second opinion is to connect the fan end of the heat exchangers to each other creating a sealed system or just to block of with a drinks can or similar item each heat exchanger. The third way (my way) is to install headers instead of heat exchangers bolted up to a Triad Weast Performance 2 in 2 out exhaust. This is the most bangs for you buck, way cheaper than all the other alternatives and very lightweight, only problem is you have no heat. If I wasn't such a wimp I would definitely take the latter route.

Left hot air duct, 930.106.321.02,
Right hot air duct, 911.106.327.00,

 

[bones]

/

 

[Bazgillie]

Bones How effective is your heater now that it is running off the engine fan and does your engine stay cool enough? Did you have to cut holes into the ducting around the engine fan? If you were going to run the car without any heating system you could cut the heat exchangers away from the exhaust manifolds this would help to dissipate the heat from the engine. On the weight saving front you could then take out all of the ducting from under the dash area but you would lose all demisting effect I know its not very good but better than nothing and needed if you use the car all year.
Baz

 

[bones]

Since I put on the 'new' heat exchangers it is boiling hot in the cockpit! At tickover there is little hot air being blown through the car compared to the blower motor's effect but on the move it's hot. Demisting isn't a problem as I avoid crap weather. Engine cooling is exactly as it was before the removal of the heater blower motor, it's only effective at low revs after about 2000 rpm the engine fan takes over. The engine fan sucks in litres of cold air on the move, the only time you will get engine cooling 'problems' in this country in an SC is on a blisteringly hot day.
There is no cutting of holes required in the ducting the only 'modification to OEM parts was to hammer the rear of the left duct to fit around the dizzy.
You can cut the HEs away from the headers within but unless you have early style HEs you won't gain any performance benefit apart from a small decrease in weight and the total loss of heat. I would always plan to combine this mod with early heat exchangers or SSIs and a performance exhaust.
Having watched a friend grind of a small cold start HE from my '73 HE system I can tell you it isn't a quick or easy job.
I'd leave the front fan in situ unless you are stripping it for track use as the fan can be useful from time to time. I don't think the weight saving would be great - but it all adds up of course, far better to junk heavy stuff like the spare wheel (buy some tyre goo and recovery insurance), the jack and carry essential fuses, bulbs, relays, fan belt and relevant tools only.