Underdrive Pullies

Topic: Underdrive Pullies (Read 2552 times) previous topic - next topic

Underdrive Pullies

January 06, 2008, 07:34:39 PM

I was bored today and since it was such a nice day (78 degrees:D ) I thought it would be a good day to take the underdrives off the 87 and try em out on the 86. I took some pics along the way... (I'm such a camera w, heheh) I didn't change out the alternator pulley, only the crank and water pump pulleys.

There seemed to be a seat of the pants difference with the change. The engine seemed to be more responsive and rev a little quicker. It didn't affect the coolant temp at all and the stereo was fine with the lights on. The dash lights would dim a little with the turn signals though (who cares).

Here's a pic of the water pump pullies. The big one is the underdrive.

The underdrive crank pulley is the small one.

And finally, the tensioner stayed within range with the stock (for my config) belt.

This is pretty basic stuff but I figured somebody might find this info useful someday. Also, you dont have to remove the fan shroud to do this job. Just leave the belt on to break loose the fan and crank bolts.

Underdrive Pullies

Reply #1 – January 06, 2008, 07:44:43 PM

sorry, i do more restoration on my car than modifications... and this is prolly a "newbie" question... but what exactly does an underdrive pulley do? i mean isnt the crank > cam a chain? and all other accessories run off the pullies? i mean im lost in the concept! can ya help a simpleton out?

Underdrive Pullies

Reply #2 – January 06, 2008, 07:54:38 PM

slows down the accessories so they have less drag on the motor

Underdrive Pullies

Reply #3 – January 06, 2008, 07:54:56 PM

The underdrive pullies slow down the BELT driven accesories. The small crank pulley reduces the speed at which the belt is being spun by the crank and allows the engine to spin more freely. The larger water pump and alternator pullies that come with the kit reduce parasitic drag by further reducing the speed of those accessories. They've been pretty well proven to increase HP across the RPM band by 7 to 9 HP.

I think I got that right.

Underdrive Pullies

Reply #4 – January 06, 2008, 08:52:47 PM

I have one of these on my Mark vii and even with a 4,000lb car you can still feel improved pull of the line. Add a K&N filter to add even more.
:burnout:

Underdrive Pullies

Reply #5 – January 06, 2008, 09:55:30 PM

i don't have a system or anything, but i have a nice head unit and decent component speakers (the head unit made the biggest difference in sound quality, for 500 bucks it better) so would this screw that up at all? what if i complimented the under drive pullies with a alternator upgrade, would that make up the difference if there was one? (also so i dont get any dimming what so ever?)

Underdrive Pullies

Reply #6 – January 06, 2008, 10:34:34 PM

I've got two 300 watt alpine amps and I have no issues at night with all the lights on. However, it's important to note that I'm using the stock alternator pulley and I have the 3g alternator upgrade. I'm not sure if it's the 95 or 130 amp version though. The car already had it when I bought it.

On my 87 bird I had a stock alternator with all 3 underdrive pulleys installed and had no problems with my Pioneer DEH P4600MP 50X4 Mosfet head unit. Turn signals seemed to be the biggest drain and even that was never a problem.

Underdrive Pullies

Reply #7 – January 06, 2008, 10:37:05 PM

O.K.,I'll go to Ebay and pick up a set asap.You talked me into it.

Underdrive Pullies

Reply #8 – January 07, 2008, 06:01:09 PM

I could use 7-10 ponys!!

Underdrive Pullies

Reply #9 – January 07, 2008, 07:33:12 PM

Update... I am having charging issues at idle with the stereo cranked up. The tach will start bouncing all over the place and if I turn the lights on the tach dies. It cant handle those two amps at full power at idle. And the alt is the 135 amp 3g.

The jury is still out but if it gets annoying I lose the crank pulley and just leave the water pump pulley on. So if you have a high power stereo I'd think twice about installing pullies.

My battery was on it's way out and I had corrosion on the positive battery cable at the terminal end. Once I bought a new battery and fixed that wire I have no more charging problems.

Underdrive Pullies

Reply #10 – January 07, 2008, 09:13:57 PM

I run MARCH underdrive pulleys on my cougar. regular old 2g alternator. ive never had any problems. highbeams on, windsheild wipers goin, radio on, radar detector on. never had any problems. sure a 3g would be better, but i dont see any need for me to switch if everything is still working fine.

Underdrive Pullies

Reply #11 – May 05, 2008, 11:40:52 AM

Question for you all.

I talked to several vendors and they said that the mustang underdrive pulleys won't work? So what did you guys/gals use?
I don't see the difference in a Tbird/cougar 5.0 and a mustang 5.0. My bird is an 88 and a masterpiece in the working.LOL

Underdrive Pullies

Reply #12 – May 06, 2008, 05:25:14 AM

Mustang underdrive pulleys work fine unless you got 3 amps but can be fixed as easy as a 3G swap after that.

Got a BBK set of my old motor and the new car i just bought only has 1 underdrive pulleys and not a full set.

So as long as you don't have a massive car audio set-up go order you a set ASAP.

Underdrive Pullies

Reply #13 – May 06, 2008, 06:20:47 PM

Since the crank turns all the accesorys I got a crank u/d pulley and im gonna run just that and see what that does.

Underdrive Pullies

Reply #14 – May 10, 2008, 02:31:27 PM

daboss351. let me know how that works for ya. The spare engine I have has just the crank UD on it. I don't have the full set so I was thinking of just throwing stockers back on it.