Serpentine fan belt conversion

[lightbulb8817]

I'm installing a 3.6L 993 motor into a 1975 911 s. The 3.6L motor I purchased didn't come with much so I'm piecing together the remaining pieces I need. I'm missing the fan, fan pulley, and crank pulley bits. I won't be running AC.

I'm considering going with the Clewett serpentine belt system and have a few questions before I make the purchase:

I will be mounting the 993 motor into my 75 car using the rennline stainless steel engine mount cross bar (2.7, 3.0L crossbar) instead of the 3.6L crossbar. As such, I will need to use the 2.7 or 3.0L engine console. Any ideas if the serpentine belt system will fit with the 2.7 or 3.0L engine console and Rennline RSR cross bar?

What is the issue with the serpentine belt system causing the low voltage light to go off? Are the pulleys sized incorrectly to not spin the alternator fast enough to properly charge the battery?

Photo attached of the Rennline cross bar on a 3.6L motor (not my photo). This photo shows the regulra vbelt (not the serpentine belt conversion that I'm trying to make work)

[willus]

I've also been considering the Clewett kit, but I don't yet have any personal experience to answer your questions. However, there is a bit of discussion on the low voltage situation here: Clewett kit finally installed! - Page 3 - Rennlist Discussion Forums

I think the 993 RS had a single belt system, but the RS was probably running fewer electronics so it could get away with less power out of the alternator. Porsche sized the alternator pulley on the standard 964/993 to support a full load (head lights, hifi audio, HVAC fans, etc) while still charging the battery at idle. (Imagine being stuck in traffic on a hot summer night - AC blowing, radio blaring, headlights on).

The Clewett pulley appears to have a ratio between the RS version and the stock version so it will get more power from the alternator than the RS, but less than stock.

I have no experience to go off of, but it would seem likely that your project car would have lower power requirements than a 964 or 993, so you'd most likely be fine?

[Bill Verburg]

Originally Posted by lightbulb8817

I'm installing a 3.6L 993 motor into a 1975 911 s. The 3.6L motor I purchased didn't come with much so I'm piecing together the remaining pieces I need. I'm missing the fan, fan pulley, and crank pulley bits. I won't be running AC.

I'm considering going with the Clewett serpentine belt system and have a few questions before I make the purchase:

I will be mounting the 993 motor into my 75 car using the rennline stainless steel engine mount cross bar (2.7, 3.0L crossbar) instead of the 3.6L crossbar. As such, I will need to use the 2.7 or 3.0L engine console. Any ideas if the serpentine belt system will fit with the 2.7 or 3.0L engine console and Rennline RSR cross bar?

What is the issue with the serpentine belt system causing the low voltage light to go off? Are the pulleys sized incorrectly to not spin the alternator fast enough to properly charge the battery?

Photo attached of the Rennline cross bar on a 3.6L motor (not my photo). This photo shows the regulra vbelt (not the serpentine belt conversion that I'm trying to make work)

Stock 964& 993 come w/ a 2 belt system for the fan w/ a 3rd for the AC.

the fan and alternator spin independently and run at different speeds in these systems, hence the belt minder to warn of a belt failure.

The RS came w/ a different fan hub that splines the alternator and fan together, like on older 911s. These systems eliminate 1 belt and the necessity for a belt minder.

w/o AC you only need a single sheave crank pulley, the 993 RS single crank pulley looks like this

the fan hub for the RS looks like this

installed like this


in the car




The RSR used a much more complicated serpentine belt system it looks like this







The single pulley/belt RS setup should be fine for most purposes, I've had zero problens in 10k mi of track use

RS crank and fan pulley is available oe or from Rothsport or Patrick

[SexOnTheBeach]

No problem with the RSR (Clewett) system whatsoever, bullet proof.

[mjshira]

I had the system and never had any issues.

[lightbulb8817]

Thanks for the helpful responses and additional photos. I picked up the Clewett serpentine belt kit today. Photos attached. Will try to get a pickup sensor bracket to read the trigger wheel.