Does anyone know what's involved in running a 3.2 or early fan/alt/shroud on a 3.6?
 

Hey there folks,

I'm in the middle of installing 964 3.6 engine in my '77 911 chassis. For a few reasons (better cooling, nicer looking heat ducts) I'm interested in mounting a 3.2 or earlier fan/alternator/shroud on my 3.6 engine.

Basically what I want to do is this:
http://forums.pelicanparts.com/uploa...1292935551.jpg

Does anyone here have any first hand experience this setup?

I've got the proper shroud on the way from Damon at Series 900. He mentioned in passing that I'd need an "early alt ring with no boss at coil mount or machine that off".

I"m also wondering what, if any, mods will need to be done to the engine harness to be able to connect to a 3.2 or earlier alternator.

Thanks for any help you can provide!

Does an earlier fan actually provide better cooling?

According to what I've read, yes! One variable which I need to check into though is pulley sizes between the 3.2 and 3.6 setup.

From Bill V:

I don't have the pulley sizes, but here are the ratios and resulting air flows
Early 911 245 mm fan with 1.3: 1 pulley ratio 1390 ltr/sec @ 6100 rpm

1976-77 five bladed fan with 1.8:1 pulley ratio 1265 ltr/sec @ 6000 rpm

1978-79 226 mm fan with 1.81:1 pulley ratio 1380 ltr/sec @ 6000 rpm

Turbo fan with 1.68:1 pulley ratio 1500 ltr/sec @ 6000 rpm

964 fan with 1.6:1 pulley ratio 1010 ltr/sec @ 6100 rpm

New twin turbo with 1.8:1 pulley ratio 1210 ltr/sec @ 6100 rpm.

More info:
http://forums.pelicanparts.com/porsche-911-technical-forum/157478-3-6-fan-blade-911sc.html

I've been chatting with Keith at Zuffenhaus about this mod (he built the engine in the pic above) and he walked me through what needs to be done. He was also willing to let me share this info with fellow Pelicans. In addition I've been looking at the PET catalog comparing part numbers between the 3.2 Carrera/964/965.

In order to pull this off what needs to be done is:

1. Source a 3.2 or earlier fan/alt/ring and machine off the rear mounting boss for the early coil.

2. Source a 3.6 fan backdate shroud from Damon at Series 900 (I believe Keith developed the mold for this part).

3. Source a turbo left heat duct and a 911 right heat duct.

4. Consider sourcing a lower crank pulley that's sized about the same as the 3.2 Carrera stock pulley. I believe the Patrick Motorsports 964/993 single crank pulley is the correct size (smaller than stock diameter 964/993 lower pulley). This is to keep the pulley ratios similar to stock and not overdrive the 3.2 fan.

5. On the 3.6 case machine off the fan strap mount bosses.

6. On the L + R heat ducts reposition the lower mounting tabs to match the 3.6 case.

7. Put it all together!

The net result of doing this mod is:

A. Fan output of ~1500 ltr/sec @ 6000 rpm vs. 1010 ltr/sec @ 6100 rpm.

B. Dual heat outlets that easily attach to heat exchangers.

C. The 911 fan sound (louder than the 964 fan).

D. It looks cool.

E. Additional horsepower is used to drive the 3.2 cooling fan. However some folks say the additional horsepower used for more cooling will actually generate more horsepower overall due to a cooler running engine.

I'm not 100% sure I'm going to do this mod but I can post pictures of what needs to be done. The reason being is I want to see if this mod is reversible. Step #5 above is what's holding me back. I'm going to look to see if there's a way to remount a stock 3.6 fan after performing this mod (this will probably require a different fan strap since the original mounting bosses will be gone).

Stay tuned! Thanks again to Keith at Zuffenhaus for sharing this info!

Oh yeah - here's another interesting link (especially page 2):

That "old" porsche sound - Rennlist Discussion Forums