stupid pulley question

[swtstang]

When you get a underdrive pulley what exactly does it do? IS it bigger or smaller than the stock one? What does it do the the rotation on the other pullies? Is it a worth while mod? Thanks in advance

[95mustanggt]

A set of pullies is designed to increase the torque applied to the belt by increasing the size of the driven pulley and decreasing the size of the driving pulley.

What this does, is makes the driven components easier to drive and therefore requires less work (horsepower) from the engine to turn.

I have heard that HP gains are between 8 and 20. What it does in real life I'm not sure, but when I get the money I'm throwing a set on!

Just remember that there is a trade off here too. Your alternator will turn slower and therefore you will have less juice returning to your electrical system. So don't have a 600 watt sound system going full blast and leave your car for an hour idling, and you'll be OK.

Hope that helps!

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Driving: 1998 F-150
Far way in Edmonton==>
1995 Mustang GT

[Stang Runner]

The pulleys are smaller. They are for your alternator, Crank shaft, and fan. They make the belt go slower. So it frees up the power that would be used to turn the belts. If you have a big sub in the car dont get them. I had one for a while and the car would stall. So I did what any real Mustang fan would of done, get rid of the SUB. Other than that if your car has lights that make it look like a X-mas tree. Go and get them.

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1988 LX 5.0
Drivetrain: 2.73 Stock Gears, World Class T-5, Lakewood Bellhousing, Summit Adjustable Cluch Quadrant & Cable, Alumminum Driveshaft, Flaming River Manual Steering Rack
Suspension: MAC Control Arms,Maximum Motorsports Front Grip Package, H&R Sport Spings, Bilstein Shocks
Engine: Steal Mounts, Ram air, K&N, Under Drive Pulles
Exhaust: 1 5/8 Un-Equal Length Mac Headers, X-pipe W\cats, Edelbrock cat\back

It's a rather cheap mod that won't hurt/help you that drastically, so why not do it. Like 98Mstg said, just don't get a kickin' system or you won't be going anywhere fast It'll get you an extra 3-5 HP, realistically no more.

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'90 LX 5.0; 12K original miles (no sh*&); 3.55 gears; pulleys;Edelbrock Performer Heads; BBK shorties; MSD 6AL box w/ blaster 2 coil; Motorsport E303 cam; Pro-M 75mm MAF; BBK 70mm TB; Eibach spring kit; Southside welded subs; K&N cone filter charger; Hurst shifter; fiberglass turbo hood; A/C-less; rear seat-less; cat-less; 2 chamber Flos; Corbeau racing seats (fronts);
30# injectors; JMS Chip; 190 lb fp; TFS track heat Intake (12.299 @ 113)

[swtstang]

The battery guage is already running a little low when the a\c is on. What about the water pump flow. Does it slow that down a lot? Thanks for all the help

[StreetStang37]

I have a dyno book and it shows like an 8 hp or so gain at the wheels, but at like 5300 or 5500 rpm and the gains (not really gains, less loss) are higher as you rev so like 4 rwhp at 3000 rpm and so on.

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1993 Mustang GT - March Ram Air & Pullies, K&N, C&L 73mm MAF, 3.73 Gears, Super Competition Hooker Headers, 2 1/2 in. High Flow H-Pipe & Cat Back, Pro 5.0 Shifter, 16* Timing Advance, 8.5mm MSD Plug Wires

[DAVISinLA]

I just had pullies installed.

Car seems to run a bit hotter, and the turn signals blink slower (due to a lack of charging at idle). I compensate for this by driving at the red line more


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'87 5.0 LX Convertible 5-spd.

Headers, cat-back, Bilstein shocks & struts, springs, pulleys, K&N filter, full-length sub-frame, strut tower brace, 3.73s. Aren't these cars great?

[1BAD89]

My latest 5.0 mag dynoed underdrive pulleys on a stock 91 LX with a k and n and FRPP Plugs and it showed an increase of 7 rwhp and 7 rwtq so..... Let the dyno tell it all.

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3:55's,BBK Off-Road H-pipe,BBK jet-hot coated equal length shorty headers,BBK 70mm Throttle Body,BBK adjustable clutch quadrant,C & L 76mm Mass air meter,Cobra R's 17x9 w/ 245's,Trick Flow Intake,Flowmaster Force II exhaust system, Super Duty T5,Centerforce II Clutch,Heavy Duty Radiator,9mm Ford racing plug wires,Accel cap and Rotor
http://www.geocities.com/i8urvpr/JM.html?987369348700

[dinomite]

The pulleys are of different sizes, the DRIVEN pulley (on the crank) is smaller so that it moves the belt less with each rotation, and the accesorie pulleys are LARGER so that they take more belt to make a rotation. This all adds up to slower accesories, and less power loss too them. When i put on my 130 amp alt, i could run all the accesories (ac, lights, etc) at idle, and be just below halfway on the volts gauge. Previous to the 130 amp, at idle, the volts gauge would be there with NO accessories on. With the underdrives, it charges a little less, so i would NOT reccomend them if you have a stock, 75amp, alternator.

[RayScopes]

O.K. to get things straight, a set of power increasing pulleys decrease the speed/torque required of the accessory belt through the use of a smaller crank (driving) pulley and larger accessory (driven) pulleys thus slowing down the speed/torque required of the accessories.

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