Difference in Pulleys from Carrera 3.2 to 3.0 SC
 

Are Carrera 3.2 pulleys interchangable with SC pulleys. Are SC pulleys interchangable with Carrera 3.0 pulleys. My assumption is yes, but can anyone confirm this?

The reason I ask is that I have friend with all the pulleys for supercharging on his 3.2 and he is willing to trade with my regular pulleys. This includes crank, fan, and compressor pulleys.

Thanks in advanced

I *believe* ( it's in my notes somewhere but they are not in front of me as I write), that Porsche used 80, 83, and 95 mm fan pulleys....and something like 120 and 130 mm crank pulleys ( 110 -120 ?) throughout the aircooled years. Fastest fan speed is with smallest fan pulley combined with largest crank pulley. I think for the 78-83 model run, that different pulley combo's were used...so I think there is more than one answer for "3.0" cars. The 84-89 Carrera's used the same crank pulley ( again...from memory) as the latest 3.0's...but there is a speed up option when using a Turbo piece,....so therefore a larger crank pulley from a Turbo might be still be available as an upgrade.
I'm sure someone with a spec book handy could corroborate this...but it seems incredible that Porsche threw in the 80-83 variation on the fan pulley, which I always thought was too small of a difference to notice... yet only causes parts mix-up problems.
--Wil Ferch

The diameter of the pulley driving the engine fan is critical. When I installed A/C in my 78SC I went to a double pulley of a smaller diameter. The result was a rise in engine temperature until I installed the right pulley. I'm sure over the years many cars have ended up with the wrong pulleys and have needed the $1200 oil cooler cure for lack of a $100 pulley!

Wil
Thanks for the info, I guess I will have to measure them. But, does this mean that they are interchangable, only that the diameter is different(and ofcourse cooling will be affected). In other words, same bolt patterns to the crankshaft and fan for all 3.0s and 3.2s.

The crank pulleys are conceivably interchangable...the upgrade to Turbo crank piece is sometimes mentioned ( others...help here please), but regarding the fan..I would think not. The fan itself creates 1/2 of the pulley..and the removable piece creates the other half. They have to mate properly, so you can't ( say) marry a 83 pulley half on an original fan that may have a 95 surface on it. The *real* problem is when you think you're OK, but find a 80 vs 83 mismatch....tough to find.. and of dubious value to have two sizes anyway...
---Wil Ferch

Looking at the fan that I just took off a 2.4TK that I'm taking apart, the inside half of the pulley is spot welded to the fan. So unless you want to drill the welds and have an alternative pulley welded on, your choices are somewhat limited.

Why did Porsche use so many different combinations? Because the engine speeds and heat rejection requirements changed. Early 2.0S's made 160 HP (HP ~ Heat) and spun to 7500 RPM. 3.2's made 240 HP and never saw anything faster then 6500 RPM. The electrical requirements of power windows, power seats and everything also drove up demands on the alternator, so as the alternators were updated, their requirements were also taken into account when determining the pulley speeds.

What timing... I'm currently working on my new Nickel plated Fan that I purchased, I noticed its pulley circumference is larger than the one I have installed on my car. The shaft hole is the same, The fan blade diameter is the same. If I use it I know I'll need to change the outter pulley what years had the larger pullies? also can anyone tell me what size belt I'll need to use?
Thanks, Jorge (Targa Dude)

The years / sizes matrix is diabolically complicated....I have the matrix at home but Automotion or other "glossy" catalogues also showed the list...I'm sure others here have it too.
---Wil Ferch

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.