I heard a lot of pros & cons on underdrive pullys. Just thought I'd give you a report. I decided to try them because they were cheap, easy to change back if they sucked and I am always looking for a little more power.

I installed mine (ASP crank & water pump pullys, new serentine belt) in about an hour. Have used them now for a month or more, all kinds of driving. Here's the report:

- Yes, the alternator doesn't charge at idle as evidence by the voltmeter dropping. But even in Atlanta traffic, at night with lights on, Hi power amped sound system, AC and windsheild wipers on, no sign of any problems with electrical system. Truck has always started and battery works as before.

- Power steering, AC, Heater, engine cooling - operating temp all as before

- More power! Nice additional seat of the pants pull... like most of my mods another nice gain that adds up.

So, if you want a cheap, easy bolt on give underdrive pullys a try... unless watching your voltmeter drop at idle makes you too paranoid.


1996 Ford Bronco, 5.8L:
-Done:Hypertech III,Powerstat, K&N FIPK,cooler TBody bypass,Mac equal length headers, Gibson cat-back, Urethane bushings, BF Goodrich TA's, Roadmaster active suspension, Nozzle lights, Euro taillights,MSD Blaster Coil, MSD Cap & Rotor, Taylor spiral pro wires, ASP undredrive pullys
-ToDo: Edelbrock performer intake manifold & 56 Tbody, Granetelli MAF, maybe Kenne Ball supercharger instead!

 

Thanks for sharing, that's very interesting. I was thinking about doing pulleys, but I figured I'd just hold on to the $200 and do something else, later on. I'm interested to see how long your battery lasts, because lead cell batteries hate to be discharged, and they usually won't put up with it for too long before they quit. If your alternator isn't chargine at idle, then it's drawing off the battery. How does your power steering feel, is it any weaker? Good to hear from you, keep us posted!

'77 F100, 302 (the aftermarket Prodigy), C4
Cadet Second Lieutenant John F. Daly III
South Carolina Corps of Cadets, The Citadel
The TorqueKing

 

Power steering is not affected. Nothing seems to be affected, yet. Your point on the battery may well come back to bite me... It's a high quality battery I purchased at a local AutoZone that has a prorated warrenty. So it's still a reasonable experiment.

The two pully set I purchased from Performancecombos.com cost only $69.95.

I'll post an update if I have anything else to share.




1996 Ford Bronco, 5.8L:
-Done:Hypertech III,Powerstat, K&N FIPK,cooler TBody bypass,Mac equal length headers, Gibson cat-back, Urethane bushings, BF Goodrich TA's, Roadmaster active suspension, Nozzle lights, Euro taillights,MSD Blaster Coil, MSD Cap & Rotor, Taylor spiral pro wires, ASP undredrive pullys
-ToDo: Edelbrock performer intake manifold & 56 Tbody, Granetelli MAF, maybe Kenne Ball supercharger instead!

 

I assume you had serpentine belt before and after putting on the "underdrive=larger pulley". So, just the larger pulleys results in a noticable increase in horse power?
Thanks.
Joe

 

Underdrive pulleys can really wake up a motor. I have them on my 1989 5.0 mustang and the only prob. is with eating batteries. If you change out the alt. pulley for the stock one things should be fine though. Took me three batteries to figure that one out! DOH!!!

 

>I assume you had serpentine belt before and after putting on
>the "underdrive=larger pulley". So, just the larger pulleys
>results in a noticable increase in horse power?
>Thanks.
>Joe

Underdrive pulleys are smaller not larger, therefore turning your accessories at a slower speed, thats why you have voltage drop at idle.

I had them on my truck for about a week, and not only did the charging drop, but I also was running hotter than usual, just my 2 cents.

ps...the power was there, no doubt about that.

cruisen

 

The underdrive damper pulley is smaller to slow the belt down. Any driven pulleys that are part of the set, usually water pump and alternator are larger so they turn slower for a given belt speed.

 

I had a set on my 5.0 Mustang, and it did not charge well in traffic, and eventually I put the old pulley back on just the alternator, if I remember right. Things were fine until the belt sawed through the water pump pulley. I guess a little bit of slippage (?) over 100k miles wears down the aluminum, and bingo, you suddenly get a very low accessory speed. It just quietly wore a wide groove until it cut off the hub.
I'm back to the factory pulleys again.

 

As far as charging goes, would putting a larger (higher output) alt. on compensate?

 

Maybe. It may be that none of them charge well below a certain RPM, though. I think that I found that I could use the original smaller alternator pulley without going to a different sized belt, and alt performance did not drop as much (it still turned slower than stock because of the smaller main pulley).

 

ASP sells an OVERdrive alternator pulley for the seperntiene(sp?) models that makes the alternator charge like normal and you allieviate the problem all together, but still have your power gain. the alternator only thake 2hp to run at full speed any way :-)

 

My ASP kit only came with SMALLER crank & water pump pullies... so the alternator pully is stock. Yes it's for serpintine system and required a different belt.

So far so good. More power, battery is acting fine. I may look into an OVERDRIVE pully for alternator from ASP. I don't remember anything on their website about that. I'd feel better if I got full charge at idle, I suppose.

Thanks for all the feedback. Havn't been to the STE site for a while.


1996 Ford Bronco, 5.8L:
-Done:Hypertech III,Powerstat, K&N FIPK,cooler TBody bypass,Mac equal length headers, Gibson cat-back, Urethane bushings, BF Goodrich TA's, Roadmaster active suspension, Nozzle lights, Euro taillights,MSD Blaster Coil, MSD Cap & Rotor, Taylor spiral pro wires, ASP underdrive pullys
-ToDo: Edelbrock performer intake manifold & 56 Tbody, Granetelli MAF, maybe Kenne Ball supercharger instead!

 

the overdrive alt. pulley does not come as part of the kit. you have to ask for it separate :-)

 

If you are worried about damaging your battery switch it out for a deep-cycle with the same amp and volt rating. It will be more expensive, but should just as long, but regardless of the abuse it takes.