[FONT=Arial]I’ve got a 15% Webb pulley installed now. Which way should I go, add a 2% crank pulley or change to 17% SC pulley? [/FONT]

 

Put the right sized belt on and go with the 17%. The crank pulley spins all of the accessories faster, increasing wear while the 17 spins just the supercharger faster.

 

IF you are going to replace it with a dampened crank pulley....your alternator will run slightly faster, as will your AC compressor, resulting in possible overcharging and extra AC wear and slighly higher parasitic losses, BUT if your current factory pulley is worn, or showing signs of impending failure....you might kill 2 birds with one stone, so to speak, with minimal or even a cost savings compared to the OEM pulley. WMW sells a nice dampened reduction crank pulley, cheaper than OEM.
IF you replace it with an un-dampened one, it is cheaper, both of the above will be true, and you MAY have additional wear in the crank bearings and seals....much debate, but the guys who built the car spent the $$ to install a dampened pulley, so I'd keep it. Jan at RMW has pic of light weight ones that have physically failed.....so it DOES happen.
If you just put a new 17% pulley on, the belt will wear faster than the 15%, so expect more frequent belt replacement, and you may still need to replace you harmonic damper in the future, but you will not loose a bit of extra HP (like with the crank reduction pulley) to the alternator running faster (and possibly overcharging you electric system) and your AC compressor will run at the right speed..not faster as with the crank reduction pulley.. running a bit faster...again, using a bit of extra HP....so total power gain in greater with a 17%....less parasitic losses, but you could break even with future savings by getting an new light weight crank pulley/damper, and get slight better throttle response due to it lighter weight....
No clear cut answers....just options to weigh.
One more thing....the Harmonic Damper/crank Pulley may be harder to remove in a garage setting if you are DIY'ing it (depending on which WEB pulley you have...I'm assuming you have the newer, Collete style one (screws, not heat+press-fit from EARLY days of randy Web).

 

Thanks Zippy. Lots of good info. I think I'll go with the 17%. My Web pully has 4 screws not 6 like some others, so I guess I'll have to get the hole piece with the collete. It should be a little easier the second time around . I do all my mods myself in the garage (when the wife is away).

 

I would go ahead and get a 17% pulley. It will be only $100, and since your pulley has already been replaced it will be easy. Plus you'll be able to get some of your money out of the resale on the 15%.

If you really want to get the larger crank pulley, go with our custom 2% oversize ATI damper. That way you won't have to worry about it coming apart, damaging your bearings, or oil pump.