Underdrive Pulley a MUST HAVE for HOs

[Archangel]

Epi, that's why Johny said you switch everything out - Mustangs use one longass belt, Panthers use two short ones. I will be using one short belt only cause I don't need the one that runs the A/C

[Blaze86Vic]

i'm all confuzzled here.

i have the stock Lopo setup, how the f am i supposed to use the mustang underdrive for this?

The underdrive pulley I linked in my first post is a direct replacement for the stock Crown Victoria crank pulley.

[1987cp]

Uslydawg (Bob) documented a .2 improvement on his car just from the pulley.

What was done to the car before the pulley swap?


Also, I just remembered something. I thought the most important reason for the underdrive crank pulley was not to spin the snot out of the water pump and start blowing green stuff everywhere. Mightn't it be simpler to use an underdriven water pump pulley instead, or is also important that the alternator not be spun too fast with the engine at 5000-5500rpm?

[Blaze86Vic]

ALL of the accessories need to be slowed down.

But there are more reasons. Having a smaller pulley makes the moment of inertia smaller, so it's easier to spin. To slow the accessories down you have to get either a smaller crank pulley, or larger accessory pulley.

[Nathan in MI]

What was done to the car before the pulley swap?


Also, I just remembered something. I thought the most important reason for the underdrive crank pulley was not to spin the snot out of the water pump and start blowing green stuff everywhere. Mightn't it be simpler to use an underdriven water pump pulley instead, or is also important that the alternator not be spun too fast with the engine at 5000-5500rpm?

You mean an overdriven water pump pulley.

Problem with doing that, other than needing to slow down all the accessories, as Blaze pointed out, is that the water pump pulley and the crank pulley run awfully close to each other as it is, so putting a pulley on there that's much bigger than stock would be pretty difficult.

[86VickyLX]

My alternator I'm running on the car now has a bigger diameter than the one that was originally on there, is that okay? That won't throw anything off right? The alternator was from a 86 towncar.

[1987cp]

Just means the alternator is currently running slower than stock, which is fine as long as it's spinning fast enough to charge the battery. The speed ratio is the inverse of the ratio of the pulleys' diameters.

[Archangel]

what mike said, I wouldn't be too concerned about it, most alternators are designed to produce max charge when engine runs at about 2000rpms anyways. Also dunno if you know, but 3G alternators have larger pulleys than most 2G, when I was installing mine I swapped pulleys cause I usually keep the rpms down low during cruise

[murphmobile2]

I'd like to see some pics of the install... any noticable power difference?

I have mine in my garage... waiting to get an HO before I even start to screw with it. I believe mine is Hawk brand though.

[Blaze86Vic]

No pics so far, I might go take some but I dunno.

As far as power...before I could spin the rear tires even if I punched it while already in gear from a 15mph roll. Now, 1st is truly a useless gear. If I have the car in first gear, driving at any constant speed, and I push the pedal, it's all wheel spin to 35mph period, in any place, any location, any surface, and thats with the 275 tires on it.

[1987cp]

Impressive. And I thought my car was pulling hard in First.

[gadget73]

Slight thread digging. I installed mine over the weekend (well, technically Scott did but lets not quibble ) and after much other assorted bs, I finally got it all together. Its definitely got a noticeable power increase. I'm hoping the underdrive will stop the exploding water pump problems I've been plagued with since I got this car. I put lucky #4 since April 2005 on this weekend.

Belts: Used a 48 1/2" (5060485) on the alternator side, and a 53 3/4" (5060538) on the AC side. I have no smog pump, just the tensioner. For those of you running a smog pump still, on the Boulevard Cruiser, the belt of choice was a 57 5/8" belt.


The alternator side really could stand to be a little longer. A 49-49 1/2" would have been excellent, but there is no spoon. I might have to try swapping on a smaller pulley off the stock alternator to get some more clearance, installing that tight belt with the 3g is a pain in the rear since the alt won't swing over quite as far as the stock one. The AC side could have been a smidge shorter, probably a 53 1/4 would have given me a bit more between the tensioner and the back side of the belt, but I had to work with available parts. One other plus of this, the AC belt no longer rubs on the water pump. In stock form, the way I had the tensioner set, the belt lightly rubbed the water pump snout, just enough to wear all the markings off the belt and make a shiny spot on the pump body.

[monterey1962]

Gadget, any updates on how your car is handling the new pulley? I just ordered mine. Will post results when the time comes.

[gadget73]

seems fine. No negatives that I can come up with, but it did take a little running around to get the right belts. Once I got that sorted out, its all peaches and cucumbers and lollypops and such. The alternator belt could stand to be longer but I made do with the parts I could get. I don't have any charging problems either, but I do have a 130 amp alternator. Not sure how well it would do with a 65.

[Blaze86Vic]

I have a 65 amp, does fine.