Alternator pulley size

[CobraMac]

So I know that you need to change the alternator pulley when you change the lower pulley. For the longest time I had a 4lb lower on so I had the 3.2 alternator pulley, when I put the whipple on I changed the lower to a 2lb lower. So my question is, what size alternator pulley do I need now? Thanks for the help!

 

[IronTerp]

The answer to your question is a matter of opinion and debate......there is no proven answer. The VAST majority of 2 lb lower users have retained the stock OEM 2.60" alternator pulley.

The 03/04' factory alternators have had a tendency to fail prematurely, regardless of the lower pulley or alternator pulley being used. Some folks feel that an "overspinning" phenomenom increases the risk of premature alternator failure. Some don't feel this way. My personal opinion is that unless you're cruising around at 3,000 to 4,000 RPM all the time, it just doesn't make that much of a difference. I ran a 4 lb lower with stock alt pulley for 15,000 miles and upgraded to a 3.20" only when I went to a 6 lb lower.

You can actually probably retain the 3.20" aftermarket alternator pulley with your 2 lb lower with no side effects.

 

[Tractionless1]

+1 keep the stock with the 2lb.

 

[CobraMac]

Okay awesome...Thanks guys! I'm going to take off the 3.2 and put the stocker back on. I have just heard things about people changing the lower pulleys and not changing the alternator pulley to the correct size and then having fuel pumps fail because they are not getting enough power or something. I don't know if this is true, but I read it on two different threads. Thanks again!

 

[Tractionless1]

............or stay 3.2, according to Lethal's site the 3.2 works with 2-4lb. lowers. Don't sweat changing it.

 

[96stanggt]

Exactly, just leave it on there.

 

[Senkak]

You may find this helpful.
I would keep the 3.2 on there.

 

[CobraMac]

Great! Thanks everyone for the help. I'm going to keep the 3.2 on there...just in case I ever decide to throw the 4lb lower back on as well

 

[IronTerp]

Senkak, isn't that old chart that PA Alternators put out that "began" the whole alternator pulley controversy??? I believe this chart was originally designed for use as an application guide for their alternators and not the Ford OEM's.

 

[Senkak]

Senkak, isn't that old chart that PA Alternators put out that "began" the whole alternator pulley controversy??? I believe this chart was originally designed for use as an application guide for their alternators and not the Ford OEM's.

I've had it in my computer for several years and I forget who it originally came from.:shrug:
I don't think it came from PA though.
It's all I have for reference.
The PA site doesn't show the chart.

 

[Jimmysidecarr]

I run a 3.2 with a stock lower. I also do 20 minute sessions on track from time to time. I wanted to slow the alt down a little, hoping it would help it live a little longer.

It's been on for WELL over a year with no ill effects. Charges fine at idle, A/C(on full) and cooling fans(on high) with headlights on, don't seem to bother it a bit.

The battery is approaching "that age" so I'm expecting to have to replace it soon, but no symptoms so far.