[Lear35A]

I have the 18# flywheel and used an S2 pulley on the front of the crank based on the recommendation of others on this forum. The reason is to reduce vibrations.

However, I notice that the 968 pulley uses 8 M6 bolts to attach the pulley to the hub which also serves as the balance shaft belt drive pulley. The S2 pulley only uses 4, yet is heavier.



I have to believe that the clever German engineers had a reason for this change (like, 4 ain't enough). Since I have now added a supercharger, which possibly puts even more load on this pulley, I am concerned.



Comments?

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[flash]

um - not sure you have the right pulley. i had the S2 pulley on there, and it used all 8



to answer the question though, yes, i too would be concerned.

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[MB968]

Interesting, when I look at the following parts manuals I see



S2 85-88 4 bolts

S2 89-91 X bolts (only has an x in the quantity column)

968 92-95 8 bolts



And the bolts all have the same part number. There are more than one pulley listed for the balance belt. I assume that some have 4 and some have 8 holes.



So, you may both be right. Even though the large bolt secures the keyed timing and bal. belt pulleys, I'd suggest finding the S2 that will accept 8 bolts for the added serpentine belt pulley loading with the SC. It looks like all the timing belt pulleys have 8 holes in them, so that shouldn't be an issue.

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[flash]

could be a tough find. last i heard, the pulley was discontinued.



you could always just drill the pulley and use all 8 screws.

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[Lear35A]

No. The pulley has 8 holes. It's the hub (balance shaft belt pulley) that only has 4 holes on my S2 part. Different design.

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[flash]

i'm confused. why are you changing? i just used the balancer pulley. it bolted right up. no other parts were needed.

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[MB968]

Yeah, why change the 968 pulley. I'd just put them side by side. I suspect that they are identical in all dimensions except the 4 bosses for holes instead of 8. If so, use the 968 part.

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[Lear35A]

That's not what I see. The pulley that drives the A/C, alternator and SC seems to be the same for both the S2 and 968. It is drilled with 8 holes. This mounts on the pulley that drives the balance shaft belt (BSB) and slides over and is driven by the crankshaft. This is the part that differentiates the S2 and 968 versions. The S2 piece I bought only has 4 drilled and tapped holes. Period. No way to add 4 more. The 968 piece has 8 designed into it.

The net result is I now have the alleged vibration dampening properties of a S2 BSB pulley. But my A/C, alternator, SC pulley is only held to it by 4 bolts. Is that risky? For some reason a Porsche engineer thought so.

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[Dubai944]

It's not the balance shaft drive pulley that needs to be changed, you should keep your 968 balance shaft pulley on there.



The S2 harmonic balancer, which is the pulley that drives the AC, alternator etc is the one you need. If that pulley looks the same as your 968 one, then I don't think you have an S2 pulley.



The S2 harmonic balancer has a rubber coupling between the inner and outer shell. 951 on left below and S2 on right. The 8 holes will bolt straight to your 968 balance shaft pulley. Maybe you got a non S2 944 balance shaft pulley, which only has 4 holes?

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[flash]

correct.



lear - i'm not sure what you are changing. the harmonic balancer from the S2 is the crank pulley.



at no time did i mess with the balance shafts. simply remove the 968 crank pulley, slightly modify the front belt cover to allow for the rear flange of the S2 pulley, and then install the S2 pulley just as the 968 pulley was.

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[Lear35A]

Ok. Call it the crank pulley. My S2 crank pulley only has 4 drilled and tapped holes. This aspect of the S2 pulley which I have (others may be different ) is a different design than the 968 crank pulley. Really I am not making this up. I may be able to post pictures later, but trust me. They are different b

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[Lear35A]

Well stupid me. Caveat emptor. And all that. Apparently I didn't have a true S2 damped pulley all along and didn't know it. Bought it from a gentleman on the forum who I see hasn't posted in a year. It was different than my 968 so I assumed it was the right thing.

Anybody have a true S2 pulley for sale?

For now I'm going to put my old 968 pulley back on there.

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[flash]

not me - sorry - i already sold it to mrmister.



the good news is that if you find one, the job is pretty darned easy.

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[Lear35A]

Yeah, simple. All you have to do is take off the supercharger and radiator fans. What's your idea of a difficult job?

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[flash]

you do not need to remove the supercharger at all, nor do you need to remove the fans.



i have a procedure to allow you to remove the crank pulley without doing any of that. all you need to do is remove the belt. if you don't have enough slack to do that, then there are 2 ways to get it. you can either remove the alternator idler pulley, or you can remove the driver side upper idler pulley. all of that can be done with the supercharger in place.



as for the fans, while it does give you more room, if you have the right size extension and socket, you can get to the crank pulley with them in place.



this entire job, including the mod to the cover, should be less than an hour.

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[Lear35A]

Got it figured out. I did get the harmonic balanced S2 pulley. But it was attached to an S2 balance shaft belt pulley. That vintage only has 4 attachment points even though the AC/alternator/SC pulley that came with it has 8 holes. I didn't know any better and put the full S2 assembly on.



Actually the harmonic pulley started to come loose (after 600 miles)! Maybe 4 fasteners isn't enough for a 968. Some Porsche engineer thought so. I'm putting the 968 balance shaft pulley with the S2 AC/alt pulley and reassembling everything. Should work now.

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[flash]

if you have the 8 and 8 combination, it should be fine. i ran it like that for quite a while.

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