Folks it must be stated that one cannot use the 993 pulley on the 964 due to the taper on the nose of the crankshaft. It must also be stated that one should not use a billet pulley without taking additional measures to straighten the 964 crank and balance it after straightening..

 

Just to be sure everyone understands I am talking in this case about the single pulley assembly at the top (at the engine fan) not the one on the crankshaft.
The triple pulley on the crankshaft is the vibration damper and is the same even unit for all normally aspirated 964s.
To replace the lower drive belt pulley with a single is not recommended without some major balancing modifications required.
Sorry for the confusion because the conversation started by Thom was really about the crankshaft pulley.
Ciao,
Adrian.

 

Thats not quite true, I have seen several 964RS w/ a single crank pulley, the owners in every case say it was stock.

Here's one


Here's another


In your earlier post you mentioned that the 993 Cup used the triple pully, that is also my observation. I am puzzled as to why, when the 993RS used a single unless AC was used. At first I thought that perhaps engines had been swapped but the owners universally claim otherwise.

 

Dear Bill,
I should not reply to peoples' posts at midnight my time. I end up confusing myself as well as others.

There are two pulley being discussed (partly my fault) the lower and the upper (under and over pulleys as they are often referred to in the USA).

The lower (under) pulley bolted to the crankshaft is never a single pulley unless you purchase a pure racing engine/Carrera RSR from Porsche Motorsports.

The 964 Carrera RS (M64/03) is fitted with the same triple lower pulley as the standard 964s part number 964 102 050 01. I have checked the standard parts cataloge (PET 5 and 6).
The Carrera RS 3.8 (M64/04) parts catalogue shows part number 964 102 150 20. I haveno time at the moment to dig up all my old RS 3.8 data and images but when I get time I will.

The standard 993 is fitted with a triple lower pulley. The Basic 993 Carrera RS is fitted with a special part number lower pulley which is basically a dual pulley.

The 993s fitted with lightweight flywheels (none of which are in the standard parts catalogue) but road registerable are fitted with the 964 triple pulley assembly (vibration damper).

I do not believe the pictures you have posted are stock certainly not in regards to the 964 Carrera RS and again seeing as the 993 Carrera RS was never exported to the USA as a road car either I would be very dubious of people in the USA or anywhere else claiming a single pulley as stock.

By the way the lower picture is not a 993 Carrera RS engine. The 993 Carrera RS has the varioram air induction system. That picture is of a model year 1994 or 1995 non-varioram engine.

The upper pulley assembly for the Carrera RS is certainly a single be it 964 or 993.

The answer I gave regarding replacement stands. The lower pulley can be replaced without removing the engine but remvoing the vibration damper requires a balanced engine for the 964 series and Kevin is quite correct a 993 lower pulley will not fit the standard 964 without serious modification. I am not familiar with the aftermarket pulley he mentions so I defer to his judgement and knowledge on the matter.
Ciao,
Adrian.

PS: The top engine is it a real M64/03 engine? I know the lower engine is not a M64/20 or M64/70

 

Yes, I am only refering to the lower


The upper pic is John Colesante's very stock 3.6 M64/03 964Cup, the lower is my mistake, it is obviously a 993, I have a lot of those pics and posted that one by mistake. It is a 993Cup, I had intended another 3.6 M64/03 964Cup w/ single crank pulley.

Yes, 993 stock and Cup use the 3 pulley sans harmonic balancer, the 993RS and 993RS/CS use 1, 2 or 3 pulley depending on the aux. used. Mine has a stock 993RS single. The 993RSR i have seen either used the single or wide single belt.

 

Dear Bill,
You are going to have to find the Porsche part numbers of the single 964RS/964 Cup and 993RS single lower pulleys to convince me.
The parts catalogue only provides one part number for the M64/01/02 and 03 engines and that is the 3-pulley version.
I do not believe that Porsche ever let a road going 964 or 993 out the door with a single lower pulley.
The 993 Carrera RS manual clearly states that the Clubsport version is fitted with a vibration damper because it has a LWF. The 3-pulley 964 version is the damper. Page 3-1 by the way.
Page 1-1 only states a shared belt drive for fan and alternator. It does not mention a single pulley and nothing in the pictures shows a single pulley either.
In the differences between the Basic and Clubsport nothing about single lower pulleys.
The 964 Carrera RS manual clearly shows the 3-pulley vibration damper fitted.
The RSRs had single pulleys but they were not standard cars and they had balanced race engines.
Andial converted USA Carrera Cups are not standard nor stock cars either.
I doubt that they ever released the road versions with just a single lower pulley either. The race cars would have probably been delivered with them but even if they did this cannot be claimed as stock or standard because these are converted race cars.
Ciao,
Adrian.

 

I have a Andial USA Cup, and it has the lower 3-pulley version running with a single belt.

 

993RS single pully 993.102.050.40
993RS dual pully 993.102.050.41 for use w/ AC



and I must re-correct myself, the lower pic in my previous post is this 964RS, I had failed to notice the rear coilpack mounts, ala 993, never seen that before on a 964 either.

 

Thanks Bill for the confirmation of the part number.
I will try and check to see if this part number was offered as standard on
any road legal cars.
Follow up: Just off the blower (yes some people are still available
on a Sunday) and I can confirm that the 993 Carrera RS Basic version without
air conditioning is normally (standard) fitted with a single pulley.
The 993 Carrera RS Clubsport road version is not fitted with a single but
with a triple off the 964. None of the 964 road cars were fitted with single pulleys.
These pics you are posting are of race cars in nation where they were never
exported to as road cars and good examples for such discussions when using the word stock or standard.
I also appreciate you going to the trouble of proving the point using factual and verifiable information. It is very helpful when people do this instead of just saying something and not providing any supporting evidence.
I am a stickler for accuracy and detail and this discussion has been very helpful to me and my 993 book section on this subject. I have actually learned something from the efforts of another and that is nice.
Ciao,
Adrian.

 

Here is a photo of the original lower pulley from my 964 Carrera Cup (series race car). The part number stamped on it is 964.102.150.00 but it does not appear in the normal Porsche parts catalog. It consists of a steel center section bolted to the outer section with 9 bolts. I have only seen one other one like it also on a 964 Cup.

 

This is a Porsche Motorsports part number and produced part.
It is not a road car component and cannot be classified as stock or standard.
964 RS parts have the last two digits modified like 01 becomes 81 and 964 RSR parts have the third set of three digits modified like 050 becomes 150.
The exception if you like to this was the 964 Carrera RS 3.8 which used a mix of standard parts, RS parts and RSR parts.
Porsche Motorsports never sold a 964 Cup or 993 Cup for the road either.
The ones that are road registered were done privately and cannot be claimed as stock or standard legitimately.
As is revealed in my 993 book, many of the genuine 993 Cups ended up as RSRs as did many of the 964 Cups before them.
When the teams ran out of Cups they started converting Clubsports and even de-converting GT-2s to RSR specs.
Porsche Motorsports North America was heavily involved with this conversion program.
Ciao,
Adrian.

 

Thanks for the clarification Adrian. Since it is a racing only part, do you know where I can get a replacement of the above pictured 964 Cup two piece pulley?

 

It doesn't show up on the Carrera Cup parts list either.

 

Damned fine question.
Porsche Motorsports or one of the major Porsche teams would be my only suggestion. There are plenty of 964 RSRs still around.
Ciao,
Adrian.

 

Gert has access to Porsche Motorsports and can supply parts available thru them. Or you can contact PMNA.