Cooling Fans

[John Clarke]

Hi gang
We are running with a late 912 engine in the 61 Coupe.(616/40)
It has the later stock 28 blade cooling fan. We have an Early 16 Blade early type in very good condition on the shelf. We run with 86mm barrels and pistons. Bursch exhaust 40 DRLA Dellorto carbs. Is there any advantage using the 16 Blade unit with fins carefully welded and unit balanced ?
Just a possible 'project / upgrade.
This for street use, never raced! Less Fins equals stronger ?
Porsche obviously saw a need for more cooling, we do have an Alloy Oil Cooler Tower and HPI remote Full Flow Filter.
TIA for any replies / advice
Regards Jay

[Mike Wilson]

Just some thoughts off the top of my head. I have read raced engines have the 16 blade fans as they are lighter and at higher rpm's deliver sufficient cooling. The other thought is that a 16 blade fan might be o.k. considering the engine has the aluminum oil cooler and remote filter. Both keep the temperature down.

Mike

[Chuck Allard]

In the late '70s-early '80s, I raced a Convertible D with ram air from the passenger headlight via 9 inch ducting directly to the fan shroud. I removed all but four blades from the fan, stripped the generator down to the shaft, used a small pulley on the crank, and removed and relocated an oil cooler to the front of the car (lots of plumbing). At speed, the engine never ran hot and the 4 blades was enough to keep it cool(ish) at idle in the pits.
When I build engines today, I put 16 blade fans on the appropriate earlier engines and 28 blade fans on the later ones. Both work with the 1720 cc kits and new aluminum coolers.

[C J Murray]

We are running with a late 912 engine

Does that mean the late 68 - 69 large diameter 12 volt generator? If so the 16 will not fit nor will a 28 blade from a 356.

There is no advantage to going to 16 blades on a street engine. Welding and balancing is a good move though.

[Paul Lima]

I'm with CJ. The only disadvantage of the 28 blade fan is the HP required at high RPM and the cavitation that can occur at high RPM. For a street engine with 6500 redline, the 28 blade fan gives the best cooling performance. Having the blades welded and the fan balanced are excellent, recommended steps.

[Vic Skirmants]

Detail information: Porsche used stock VW fans. When VW decided they needed more cooling, they went to 28 blades. Therefore Porsche did also.

[Alan Klingen 2]

They all sound good to me BTW if you are running an external cooler all the line help in the cooling process this shown to me by my late mentor Juergan Kirberg. Alan The Stable.