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I need to replace the old and nasty pullys on my 65' FB. I only have a crank pully, waterpump and alternator. Do I get the underdrive set-up from March or do I get some standard - non underdrive aluminum pullys or the such. Will Underdrive pullys be a bad thing? Will it cut down on Alternator output when you slow down the rotations? Kory

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All depends on you. Definately not stock! But you should notice an improvement in the seat of your pants. I just put a set of Ford Racing underdrive pullies in SWMBOs 94 GT and you definately can feel the difference. She was pleased. For sure your alternator output will go down....

TJ - Highland Village, TX (DFW area)

66 coupe 302 2v c4 -daily driver
94 GT vert -SWMBO's
93 Aerostar - hauling stuff
50 Mercury Pickup - waiting to be restored, stored back home
 
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Kory,
Under-drive pulleys may be great for the late model Mustangs because they have so many accessories to drive but for a classic Mustang I do not see the benefit, it does not take any energy to turn your alternator. I would be more concerned about the reduced speed of your cooling fan and therefore the possibility of over heating at stop lights on a hot summer day.

By the way, thanks for the seat belt input.
Kevin
 

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Sorry, but have to disagree. Take a look at how many dragsters have an alternator ... they DO rob horse power.

I have the March Underdrive pullies on my '66 coupe and love them. Can't say if there was any performance difference since I've never had any other pullies on this car, so don't have a base to compare against. The alternator output is no problem, but as you said, the slower spinning of the fan/water pump is a little problem on days when the temp exceeds 100 degrees. Anything below about 98 degrees and cooling is not a problem either.

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