Overdrive Alternator Pulley Installation: 4.0 SOHC

[aldive]

In an endeavor to resolve my charging voltage at idle quandary ( http://www.explorerforum.com/forums/...ght=alternator ),
I ordered an overdrive alternator pulley from Underdog Performance ( http://underdog-performance.com/index.html ). Of course it had to be red to match my underdrive water pump pulley (http://www.explorerforum.com/forums/...ght=underdrive ).

The pulley cost $40.00 delivered to my door.

For those who don’t understand underdrive/overdriving, let me reiterate; to underdrive the crankshaft, you use a smaller ( than stock ) diameter pulley, whereas to overdrive the alternator ( or any other accessory ), you also use a smaller diameter ( than stock ) pulley; a larger pulley on an accessory would underdrive it.

My 130 amp alternator ( http://www.explorerforum.com/forums/...ght=alternator ) is being underdriven via the UDP/harmonic balancer ( http://www.explorerforum.com/forums/...ght=underdrive ); this overdrive pulley should restore the alternator speed to stock and restore my idle voltage issues.

To facilitate access ( since my air impact wrench would not fit with alternator attached to the motor ) to the alternator pulley retaining nut, the alternator had to be removed.

The first step in this mod was to disconnect the negative terminal of the battery. My Mac Intake ( http://www.explorerforum.com/forums/...ght=mac+intake ) was then removed to gain access. The next step was to remove the serpentine belt by rotating the drive belt tensioner counterclockwise with a 3/8” breaker bar. Now the wire harness to the voltage regulator was unplugged and the B + terminal cover lifted and the nut (10 mm) and wire ( also the supplemental 4 gauge wire [ http://www.explorerforum.com/forums/...ght=alternator ] removed. The 3 bolts ( 13 mm ) holding the alternator in place were detached as well as the additional grounding wire; then the alternator was detached from the truck. Air tools made removal a snap.

Subsequently, the alternator was padded and placed in my bench vice and the pulley nut (15/16”) removed with my air impact wrench.

The stock pulley was 2 9/16“ in diameter, whereas the overdrive pulley was 2“ in diameter. In contrast, an underdrive alternator pulley is 2 5/8“ in diameter.

The overdrive pulley was installed and the nut tightened with the air impact wrench and torqued to 80 ft/lbs. After that the alternator was reinstalled in the truck by reversing the removal procedure. A new ( size ) serpentine belt was not required for this mod, nor did I feel the need to replace the existing belt since it’s only a few weeks old. NOTE: after a couple weeks, the belt started squeeling; it was resolved via a 5060850 belt.

The motor was started and observed for any troubles; none were present.

After allowing the motor to reach operating temperature ( 190 F ), the voltage at idle was 13.4 volts ( as determined with my Dakota Digital [ http://dakotadigital.com ] voltmeter ). Idle voltage prior to the new pulley install was around 12 volts. The voltage at 1000 rpm was 14.0 volts. A short road test at 70 MPH, showed the voltage to be as before (13.9 volts) the mod. This test was in the daytime with high beam lights, the stereo/amp on and the AC blower on high.

This simple and inexpensive mod took about 30 minutes at a unhurried pace.

Finally, the voltage at idle problem appears to have been resolved. This sure beats purchasing an expensive new alternator ( even though a glistening red one would be nice ) that might have the same idle voltage issue.

[BrooklynBay]

Al, is there a mathematical formula that is used to calculate the pulley sizes according to the pulley's diameter? How much faster would a pulley like this make an alternator turn? I'm just wondering if there would be any improvement to use this pulley along with a stock engine pulley.

[techieman33]

Will the bigger pully increase drag? Hurt your gas mileage?

[aldive]

Originally Posted by techieman33

Will the bigger pully increase drag? Hurt your gas mileage?

A larger in diameter pulley is an underdrive pulley. It "should" slightly improve HP as well as gas mileage but it will cause voltage issues at idle. I tried one.

[aldive]

Originally Posted by BrooklynBay

Al, is there a mathematical formula that is used to calculate the pulley sizes according to the pulley's diameter? How much faster would a pulley like this make an alternator turn? I'm just wondering if there would be any improvement to use this pulley along with a stock engine pulley.

An overdrive alternator pulley might help with a stock crank pulley; worth a try for $40.

Good luck ....

[spindlecone]

Originally Posted by aldive

An overdrive alternator pulley might help with a stock crank pulley; worth a try for $40.

Good luck ....

Beg to differ Al, it will not help with a stock crank pully, and it is not worth 40 bux.
I am amazed that you had a charging problem with the ASP underdrive crank pully.
Out of many people that have done this mod, enc me, long before you did.
Nobody has ever had a problem as to alternator output, it has never exsisted, prior to your install

[aldive]

Originally Posted by spindlecone

Beg to differ Al, it will not help with a stock crank pully, and it is not worth 40 buxl

Once again, you knowledge of pulleys is lacking. Why not give it a rest; all you want to do is stil up trouble.

A smaller in diameter alternator pulley will overdrive the alternator and "possibly" help with his voltage issues.

[spindlecone]

Originally Posted by aldive

Once again, you knowledge of pulleys is lacking. Why not give it a rest; all you want to do is stil up trouble.

A smaller in diameter alternator pulley will overdrive the alternator and "possibly" help with his voltage issues.

Am not in any way trying to stir up trouble Al. and in all fairness, next time you Quote my post, please do so in its entire context.

[BrooklynBay]

I once saw a pulley advertised somewhere that was as small as a cylinder with raised sides. It probably had the highest ratio available. I don't remember who made it.

[96limitedX]

Al, thanks for the write up! i'm hoping to order one of those pullys soon. i'm having issues after a new alternator that came with a bigger then stock pully.

anyway looks good and thanks

[96limitedX]

well i orderd my alternator overdrive pully tonight. i'm really concernd about getting the old pully off tho. how exactly do i do that without destroying it?

thanks Al nice write up.

[aldive]

Originally Posted by 96limitedX

well i orderd my alternator overdrive pully tonight. i'm really concernd about getting the old pully off tho. how exactly do i do that without destroying it?

thanks Al nice write up.

On mine, it was very simple; I just put my air impact wrench on it and that did the trick.

Good luck ...

By the way, where did you get yours?

[96limitedX]

from the site in your link...

[aldive]

Originally Posted by 96limitedX

from the site in your link...

Great; be sure to post how it works for you.

[whoathere]

does overdriving the alternator shorten its life expectancy?

[aldive]

Originally Posted by whoathere

does overdriving the alternator shorten its life expectancy?

I doubt it at normal speeds and RPMs; however, if one revs the motor a lot, I bet it would.

[96limitedX]

uhoh..lol i have alot of 5000rpm shifts..haha

yea i'll post how it turns out..i cant wait for it to get here.

[aldive]

Now that I have had the overdrive alternator pulley installed for 2 weeks, the belt has started to slip and squeel.

Tomorrow I shall get a 1 inch smaller belt since the pulley difference is 9/16'.

[96limitedX]

i got mine installed (week and 1/2) with a 1 1/2" smaller belt. i'm loving it..absolutly no voltage issues anymore stoped in gear with all accys on. thanks Al for the link.

[aldive]

Originally Posted by 96limitedX

i got mine installed (week and 1/2) with a 1 1/2" smaller belt. i'm loving it..absolutly no voltage issues anymore stoped in gear with all accys on. thanks Al for the link.

What belt number did you use?