underdrive pulley fitment issue on 3g

[mob]

Hey guys any of you ever had this problem? I have a 3g alternator I got new from a parts store. The pulley that came on it worked perfect on my stock setup. I just ordered a set of under drive pulleys from someone online, and got them in today. When I put the pulley on it rubs against the alternator case, and the stock pulley has about 1mm of an extra lip that lets it spin freely. There is no way this can work like that, and it probably wont even line up with my belt. Do they make some kind of spacer for it? I really would like to run all 3 under drive pulleys. Let me know if anyone has had this problem and what you did.

I think they are BBK pulleys. They are black steel ones so I dont know.

 

[Mustang5L5]

It's common.


I used a washer as a spacer. Not sure what size. Measure the shaft. I wanna say 5/8" but not sure.

 

[Saleen0679]

My stock 2G alt came with a spacer behind the pulley. It wouldn't have worked on a 3G without the spacer. The March UD alt pulley compensates for the spacer so it wasn't needed. I must depend on who makes the pulley set and if their design has the spacer thickness built in.

 

[mob]

Alright thanks, I measured the width of both with a mic and the underdrive is like .05" smaller. I'll have to see what washers I can find that wont through off the belt lining up.

 

[mob]

My stock 2G alt came with a spacer behind the pulley. It wouldn't have worked on a 3G without the spacer. The March UD alt pulley compensates for the spacer so it wasn't needed. I must depend on who makes the pulley set and if their design has the spacer thickness built in.

Well a 2g doesnt need a spacer either way because if the pulley is touching the fan, it will just spin with the fan. On the 3g the case doesnt spin. But I see what you are saying about the design, i will just have to find a washer.

 

[Saleen0679]

Well a 2g doesnt need a spacer either way because if the pulley is touching the fan, it will just spin with the fan. On the 3g the case doesnt spin. But I see what you are saying about the design, i will just have to find a washer.

On a 2G without the spacer you would shift the pulley and throw off your belt alignment if the spacer wasn't compensated for. My spacer here is a tad bit short of .06.

 

[67coupe]

With most underdrive pulley sets:

Crank is smaller than stock (spins all acc slower)
Water pump is larger than stock (spins slower)
Alt pulley is SMALLER than stock (spins a little faster to keep low RPM charging)

A stock 3G pulley is LARGER than the stock 2G and much LARGER than the under drive pulley. This is why most underdrive alt pulleys will not fit on the 3G.

What I've done is use the stock 2G pulley on the 3G with my underdrives. This is still spinning the alt slower than it would be with the underdrive pulley. Since it's a 3G, there are no low RPM charging issues.

I know people who have used the stock 3G pulley with underdrives. Spinning the alt even slower than the stock 2G size. Still no charging issues.

In both cases, you can still use the factory belt length.

 

[mob]

So they just use the smaller pulley on the alt to make up for charging issues not for "performance" is what you are saying? I have always been confused as to how underdrive pulleys work. Moviing everything slower is the goal right? So if I use the 2g pulley it will go slower and if I use the 3g pulley it will go even slower right? I am not too worried about charging issues, so if I use the 3g pulley I will get the most "performance gain"?? If I have problems I can always just swap pulleys.

 

[Mustang5L5]

I use an OVERDRIVE alt pulley on my 3G. It's a 1 7/8" pulley smaller than the stock 2G pulley.

When driving pulleys, (crank), the smaller you go, the slower everything turns. With driven pulley, smaller pulleys equals more rotations per crank rotation.

Reason i use the O/D alt pulley is to speed the alt back up at idle.

 

[67coupe]

So they just use the smaller pulley on the alt to make up for charging issues not for "performance" is what you are saying? I have always been confused as to how underdrive pulleys work. Moviing everything slower is the goal right? So if I use the 2g pulley it will go slower and if I use the 3g pulley it will go even slower right? I am not too worried about charging issues, so if I use the 3g pulley I will get the most "performance gain"?? If I have problems I can always just swap pulleys.

Yes...some kits come with smaller alt pulleys for this reason. The stock 2G is bad enough at idle. Spin it with a smaller crank pulley and the problem is magnified.

Yes. As Mustang5L5 said, reducing the size of the driving pulley (crank) turns everything slower. Increasing the size of a driven pulley (water pump), also turns that accessory slower. Conversely, reducing the size of a driven pulley (alt) will increase the speed. Ever had an 18 or 21 speed mountain bike? Same principle.

Yes. I use the 2G alt with my 3G and ASP underdrive pulleys. With all accessories on and electric fan on high speed, I'm at 13.1 volts at idle. A friend is using the stock 3G pulley with ASP underdrives. 12.8 volts at idle.

Unless you have electrical loads out of the ordinary (I consider an electric fan ordinary), the 2G or 3G pulley should be fine.

 

[Mustang5L5]

Unless you have electrical loads out of the ordinary (I consider an electric fan ordinary), the 2G or 3G pulley should be fine.

Or an AOD, as they tend to idle lower than 5-spds while sitting at a stop light in gear. That is why i ran an OD alt pulley. When i had the AOD in my car, the difference in RPM from Nuetral to Drive was enough to bring the volts to under 12V. I needed the OD pulley for that extra RPM at low idle.

Now that i'm a 5-spd, i'll prob toss the other underdrive pulley on for the sake of having matchning pulleys.

 

[67coupe]

Under 12V with what alt? If 3G.....WOW!

 

[mob]

KK thank for the help guys, I'll prob stick with the 2g pulley and see how many volts I am putting out. As of now I am using the stock clutch fan, but nothing other then the stock stuff like radio and lights. Probably going with a electric fan soon.

 

[Mustang5L5]

Under 12V with what alt? If 3G.....WOW!

Yes, but with underdrive pullies, an SN95 electric fan and an AOD.

The OD alt pulley fixed that issue, just needed a few more RPM.

I'm gonna take it off now

 

[67coupe]

At what RPM did your engine idle with the AOD?

Just for future info, I have the stock 2G pulley on my 3G and with a Taurus fan at full speed, I have right at 13V.

 

[Mustang5L5]

I can't remember, it's been 6 years or so. I wanna say 600 or so RPM but that's by the stock tach and who knows how accurate that is. But the 100-200RPM jump fron neutral to Drive did make a difference in charging.

I don't need it now with the 5-spd, so i'm gonna take it off so i have matching pulleys.