Hey Guys,

I am looking to change over to the smaller 356 alternator pulley.  I will also add a welded and balanced fan.  Does anybody know what size belt to use with the 356 pulley?  Also any recommendation on where to buy a good welded and balanced fan at a reasonable price?


Original Post

Yeah. I wouldn't down size the alternator pulley with a stock 7" crank pulley. Even with a balanced and welded fan you could explode it.

If you go with the 356 alternator pulley, you'd want the appropriate size crank pulley to keep fan speeds just right. I'd get a power pulley which is around 6" or so.


It's been a while since I messed with a power pulley, but the crankshaft power pulley is smaller in diameter than a stock (6-3/4") VW pulley, which would make a stock sized alternator/fan pulley spin slower, thereby giving you a bit more power feel.

A 356 fan pulley is slightly smaller which, given a stock VW crankshaft pulley, would spin the fan faster.

I'm no way sure, but combining a power crank pulley (slower fan) and a 356 fan pulley (faster fan) might just get you back to where you started for fan speed.

If you want a faster fan, (and why do you want that, might I ask?) then go with a stock crank pulley and the 356 fan pulley.  That should increase fan speed about 15% IIRC.

Don't forget to get the Berg welded, balanced fan to go with it, just in case you drive like Danny P. or Mike Pickett, up around 7 thousand rpm......        See Mike's long thread elsewhere on here, about rebuilding his engine after a cataclysmic fan detonation in sleepy old Hawaii.  If he can do it where his (legal) speed limit is around 35mph, then you can too.

On the belt size, many auto parts stores (NAPA for sure) have a fan belt measuring device.  My suggestion would be to take your old/existing belt to the NAPA store and ask them for the next two smaller sizes and get them to take back the one you don't need after you've tried installing it.  If unused, they should.  Any decent VW service manual will tell you how to install both the fan pulley and the belt for proper tension.  If not, let us know and we'll give you at least a dozen different ways of doing it - some may even be right.

The stock, dual-port engine fan belt (which you now have) should be:

9.5mm - 11.3mm wide by 905mm long.  You want a shorter one.

I would also strongly recommend the thicker belt, like an 11.3mm instead of the 9.5mm puppy.  It'll last a LOT longer.

Last edited by Gordon Nichols

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