.

 

fd alt to fc i mean

 

If it helps you, visualize the two pulleys (e-shaft and alternator) as direct coupled gears (since they are functionally identical).
Say the ratio is 5:1, the alt gear (pulley) makes 5 revolutions for each revolution of the drive gear/pulley.
Since the alt shaft is affixed to the alt pulley, it too will spin five times- no matter if the shaft is 2" diameter or 1/2" diameter.

Maybe a little but what are you going to do?
Remember, the two pulleys use different belts, so the OD is not directly comparable anyway. I'm not sure how one computes the effective OD of a v-belt pulley but in practice I think they're pretty damn close.
The alternator doesn't seem to mind.

 

I bought a dual alternator pulley from Innovative for my FC alternator, soon it will be a real boy...er I mean an FD alternator swapped in.

I had trouble with belts also. The problem being it's hard to find similar length belts even in the same brand belt. There is some variance in their length. I ended up buying every Gates XL belt my local auto parts chain carried at all the different stores (4 total). What I found was that even within the same brand there was different construction. Two of my belts had an inner reinforced layer on the pulley side and 2 did not have that layer....all of them Gates XL belts though. 2 of each kind were similar in length to each other and I matched them up and returned the other 2.

 

I got my fd alt with plug (i have s4) and the double pulley already mounted from silverrotor. Brand New!

 

One negative I've found is, after installin an FD alt, my cheap eBay strut-bar no longer fit.
not that bit a deal though, since I just traded the bar away for some other parts.

So does anyone Have a Strut Tower Bar that will clear an FD Alt?
What kind ? & post pics please.

 

My FD Alt swap is not going so good.

I have the new S5 plug and the double pulley from Banzai. I bought an FD alternator from Auto zone.

When I put the pulley on the FD Alt it binds on the housing. I need a shim or washer ( oddball size and hard to find ) or I need to grind/clearance the Alt housing. It has a small ridge, maybe 1/8 of an inch, that might allow the pulley to spin without a shim.

Still waiting to get the 100 amp project working.

Rob

 

that shim is deffinatly needed, if you look at the stock pully you can get the dimensions of the spacer that is on the back of that pully and probably find something, somewhere, havn't started looking for that yet myself...

and i think the spacer would be required becuase without it the pully will not line up with the water pump and main pully, cuasing your belt to snap

 

Not a clue what brand this is, sorry.

 

I couldn't find it doing a search, but I remember reading that someone used a spare crush washer from their oil cooler lines as a shim.

 

As has been stated by several people, it makes no difference. The outside diameter is all that matters.

Only if you get a pulley that's a different outside diameter. The stock FC and FD pulleys are very close in size.

Genuine Infini strut bar. See pic in sig.

 

The bar in that pic is a corksport bar.

 

The above is what I did and have been running strong for a week. Drove about 400 miles over the weekend as well.

GG