I've read that underdrive pulleys can give you up to 20 extra hp. Are they a good modification? How hard are they to install and how will it affect the performance of the air conditioner, alternator and power steering?

 

There are some people here who feel that they provide a noticeable increase in performance. Maybe they will respond.

Personally, I would find the 20 HP hard to believe. I would want to see some real dyno readings to back that up. Additionally, I would not want to reduce my alternator output. An alternator is quite efficient in that it does not add much to the load unless the system needs to draw current. In other words, under "racing" conditions, it would not be much of a drag. And of course, your AC would be off. That leaves the power steering and water pump/fan. Can't believe the PS would make that much difference. Don't think I'd want to slow the water pump when racing. Would the fan make much difference? Maybe, but not 20HP. It seems like an electric fan might make more sense, but others here have said they don't provide significant performance increase although they can solve overheating problems. And some load would then be added to the alternator.

In short, it doesn't seem like it could help much, and might cause problems in daily driving.

 

You will gain about 10 hp at higher rpm's (around 5000). Your alternator will not charge as good at an idle and the coolant will circulate more slowly thruthe system. The power steering will not be effected much.
I run an underdrive pulley on my Mustang and it doesn't fully charge until about 1100 rpm.
Jimmy

 

20 hp is laughable! I read a test in one of the mustang mags with dyno results on every bolt-on for a 4.6 2V engine. This is identical to the truck engine except the intake manifold, as far as I know. The pulley they installed netted them about 3-4 hp at the top end. Of course the pulley ratios may be different on trucks, but I wouldn't expect more than 5hp.

I wish I remember the title and issue of the mag, because it was great info about what worked and didn't on the 4.6...

 

s.hamstack, it would be nice if you could remember the mag that the article came from. It would be great to know what works for the 4.6 and what isn't worth the money.

Do you recall what kind of gains were achieved with an after market air intake?

 

I'll check with my friend that had it this weekend and post it. In reality none of the blot-ons helped that much, and some even hurt on near-stock applications. The best one was the cat-back exhaust, that netted about 10-15 hp and it was downhill from there. They did end up with well over 300hp but that included a new intake manifold and reworked heads and cost them over $5k.

If I recall correctly, the new intake elbow/ cone filter got about 7-8 hp for them but I'll post the mag and issue so everybody can check it out with their own eyes...

 

Thanks

 

Yeah, the article I saw was something like that. They changed a bunch of stuff on a stang and didn't gain much power, and it detonated to boot.
I will look for it. They used a bullitt Mustang I think.
Jimmy

 

The one I saw was in the Feb 2004 issue of "5.0 Mustang and fast fords"

The underdrive pulley netted 2.3 hp.

 

I looked into the March pulleys for my 6.4L. I doubt it would have netted me 5 hp.

 

you won't get much power out of pulleys on a mod motor, ford was very agressive from an oem standpoint with pulley sizes and weight.

JH