I think I've got the basic concept - less power for the accessories, more for the drive train.

I looked at howstuffworks.com and couldn't find the answer. When I do the search hear I get a 1000 "I did this mod..."

What I'd like is a pros and cons explination. If this is such a great idea, why doesn't it come as an option.

Thanks

 

Underdrive pulleys do exactly that...they underdrive the crank pulley. It is like using the smallest sprocket between the pedals of a ten speed bike. Easier to turn, therefore freeing up horsepower.

The trade off... all other things being equal... is that now you are driving the belt slower per each revolution of the pulley, so you need to use slightly bigger pulleys on the waterpump and alternator, or you will underdrive them at idle and risk not charging and overheating. This was far more prevelent on old 5.0s as their original alternators were rated at 80 amps. The newer cars are less prone to this because their alternators are bigger and water pumps are more efficient. I believe the bullitt mustang even came with underdrives from ford.

Unless you live in a climate that constantly stresses the alternator or cooling system, I don't think there is a down side. Ford has to build cars that run for everybody.

I have heard some report a cel after installing them on the '05, though. Good luck!

 

Thank you Smitty!

I've posed this very question a couple of times, and that's the most detailed concise explanation I've heard to date.

I live in one of "those areas" that stress the heck out of cooling and charging systems, and that was my main concern, as I too deducted that it probably wouldn't be a good thing to do for a daily driver. Especially when we're only talking about 10 hp. Doesn't seem worth the risk to me.

Thanks

 

I live 90 miles north of Sacramento and it hits 100+ most of the summer months. Probably not a smart move for me to do either.

 

You can have the pulley replaced on your alternator to make up for the change and bring charging back up to par.

As for the water pump, I have seen many underdrive pulleys on cars in S. FL with no problems, LT1 V-8's, 6 bangers and 4 bangers, no cooling problems. You have a thermostat that opens and closes for flow, and I can't imagine that Ford designs the cooling system so that the thermostat is open fully at all times.

I'm not sure how the fan setup works, but you could also wire the fans so they run whenever the key is on.

Also, another reason for the pulleys, at least on other vehicles is to reduce the rotational inertia. For every pound of valvetrain taken off, it is supposed to be equivalent to 6 pounds out of the car. For drivetrain, 1 pound equals 3 pounds. So when you put those wheels on your car that way 10 pounds more a piece, that is 120 pounds. The other pulleys are usually made out of billet aluminum, so there is about a 6-10 pound loss. I am sure there is more of a theory behind it, but that is what I have read.

Just something to think about.

 

No offense, but S. Florida is not hot. It's uncomfortable, and I wouldn't want to do it without A/C, but there's nothing like dry desert heat!

Now 110-120+.... ambient air temp, road temps appraoching 200 degrees on asphalt
(Yes, local news crews fry eggs on sidewalks every summer, just for the heck of it)

THAT'S HOT

 

The desert is not the place to play "chicken" with your cooling system!
You want your car to be your friend! Your very best buddy!

 

Yeah, but we have humidity. Like 100% humidity. I have a couple friends in Vegas, they said they would take 20 degrees hotter there than the 100% humidity in FL. But, I guess for our cars sake, that doesn't mean much? Just makes it stink for the driver if the AC doesn't work.

 

Yeah, I absolutely hate humidity!

My main concern is air conditioning. I don't want it running at less than 100%. When temps get in the 110-120 range, some cars start to have problems keeping the car even marginally cool.

I don't know how on earth I ran without A/C in the 66.... young and dumb I guess!

 

Yes, as 66 said a very consise and to the point answer. Thank you.

 

I ran a underdrive crank pulley for nine years now on a 95 Firebird Formula. I had to replace the pulley on the alt. to speed it up. Never had any problems with alt. or cooling in Chicago. The only thing I had to do is take the auto trans out of gear at a long stop light or train crossing and speed up idle with gas pedal, but only at stops I knew were going to be long , normal stops never did it .