3.6 Crank Pulley

[VincentVega]

I need a new crank pulley for my 3.6. Several of the allen bolts worked loose and the pulley has nice oval holes for mounting points.

It's too late to call the dealer, or Pelican for a price, so I'm looking for my options. I see 2 choices, either replace w/ the same Porsche part, 964 102 150 00 , or go for an alternative from Patick Motorsports or some one else. It doesnt look like the stock 'big' pulley will fit in the car with the stock sc crossmember, I had to remove the crossmember to get the pulley out; tight fit.

Any suggestions?

[Bill Verburg]

If this is for a 964 you do know that the factory pulley incorporates a harmonic balancer, the 964 crank does whip a bit. The aftermarket do not. You can run the non balancer pulley, the result is increased NVH and possibly reduced safe rev limit and or crank life, the factory did this on a very few 964 race only cars but the mtbr(mean time between rebuilds) was very much reduced. The 993s had a substantally beefed up crank to eliminate the balancer.

[DW SD]

Bill,
If you have the complete rotating assembly dynamically balanced, in your opinoin, is it safe to run a 964 bottom end without the harmonic balancer?

Mine was spun balanced by House of Balance (los angeles, CA) and doens't have the harmonic balancer any longer. The engine hasn't been fired, yet, but I'm moving that direction.
Does anyone make a smaller harmonic balancer than the factory 12 lb (guess) beast? In the Chevy world there is fluidynamics (I think) who makes some nice one, which are also small and relatively light rotating mass.

Doug

[VincentVega]

Thanks, good info. This is the way the car was, so at least for now I want to get it back together, first event in a few weeks.

I might look at changing the pulley to stock, but I believe that will require using the 964 mount, or at least more work than I have time for now.

[Bill Verburg]

It's not a matter of balance at all. It's a matter of a harmonic or resonance point caused by the crank at some point in it's rev range. The factory went to great lengths to stiffen the 993 crank to get rid of it.


A very few Cups were run w/o the balancer so it can be done, the question then becomes what are the long term consequenses. I have questioned factory engineers, team mechanics and owners they mostly just comment on the increased vibration levels.

[VincentVega]

Thanks again Bill!

Do you happen to know the depth of the stock pulley?

[Bill Verburg]

No, but it sure does look big w/ all 3 sheaves

[911teo]

Originally posted by Bill Verburg
It's not a matter of balance at all. It's a matter of a harmonic or resonance point caused by the crank at some point in it's rev range. The factory went to great lengths to stiffen the 993 crank to get rid of it.

A little off topic but is this why you prefer the 993 crank to the 964 crank? I have lots of different opinions on this one...

[Bill Verburg]

Originally posted by 911teo
A little off topic but is this why you prefer the 993 crank to the 964 crank? I have lots of different opinions on this one...

That is a biggie, there are others

[JasonAndreas]

Originally posted by Chris Martin
Do you happen to know the depth of the stock pulley?

Do you want the inside depth? Front? back? the radial depth? outside dimensions? I have one sitting right here just let me know exactly what you want measured.