pullyes
Elder User
Joined: Oct 1999
Posts: 917
Likes: 3
From: Kelseyville USA
pullyes
Underdriven pullyes,what is that,and how are they working?
Such as....
If the Supercharger pulley is smaller then the crank pulley ..you would be OVERdriving the supercharger..that is turning it Faster than crank speed.
If the pulley on the supercharger is Bigger than the crank pulley then you are UNDER driving it...
And so it is the same for anything you `Drive` with a common pulley (like the crank pulley)
When you here a drag racer say he is 10% overdriven ..now you have an idea !
__JOHN__Õ¿ö
FTE Club #7
Member-
http://www.cruisin-north.com/
Santa Rosa, Calif.
72 F-250
ICQ#6030753
http://www.ford-trucks.net/users/jbhf250/
https://www.ford-trucks.com/pictorial/big/1972_f250_2.html
Post Fiend
Joined: Feb 2001
Posts: 6,624
Likes: 8
From: Missouri
pullyes
Underdrive pulleys are just pulleys that are different sizes than stock. For instance if you put a bigger pulley on your alternator and power steering pump they will turn slower therefore taking less power to turn. The disadvantages to this are less power for power steering and less charge from your alternator. Also if you underdrive your cooling fan you can get into cooling problems.
Cargo Master
Joined: Mar 2001
Posts: 2,759
Likes: 71
From: Elk River, MN
pullyes
When you reduce the crank pulley diameter, it slows down the belt speed and all the accessories run slower, perform at less than normal and take slightly less HP because they are not working as hard. Don't confuse belt speed with RPM, think of something big like a propeller with belt wrapped around the tip and how fast the belt would move compared a belt wrapped around the hub that turns at the same speed. Most underdrive pulleys are in the range of 10% less belt speed than normal. You would be giving up 10% engine cooling, alternator charging, power steering, air conditioning, etc.
Thread Starter
|
New User
Joined: Sep 2001
Posts: 10
Likes: 0
Trending Topics
Junior User
Joined: Mar 2001
Posts: 94
Likes: 0
From: MONTANA
pullyes
I put them on my 1990 F250 351 E4OD. It felt like I unloaded a 1000 LB load. Big gain! Very noticible.
But shop around. $60 - $90
Good Luck!
Larry
But shop around. $60 - $90
Good Luck!
Larry
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
Post Fiend
Joined: Feb 2001
Posts: 6,624
Likes: 8
From: Missouri
pullyes
Just making the crank pulley smaller won't be the optimal setup. You may be able to comfortably remove a certain amount of speed from one accessory and a whole lot less from another. Buying the whole kit is what's going to make the most power/functionality.
Freshman User
Joined: Sep 2001
Posts: 25
Likes: 0
pullyes
When you reduce the crank pulley diameter, it slows down the belt speed and all the accessories run slower, perform at less than normal and take slightly less HP because they are not working as hard. Don't confuse belt speed with RPM, think of something big like a propeller with belt wrapped around the tip and how fast the belt would move compared a belt wrapped around the hub that turns at the same speed. Most underdrive pulleys are in the range of 10% less belt speed than normal. You would be giving up 10% engine cooling, alternator charging, power steering, air conditioning, etc.
You will not necesarily lose 10% cooling. It may turn the water pump 10% slower, but that gives the water in the radiator more time to cool, thus making the engine run cooler. At least, that's in theory anyway. I have used a set before on a staoutly built camaro and it still cooled just fine (using a flex fan, no electric), power steering was fine, and charged fine, except it wouldn't charge great at an idle. but as long as i was moving everything worked fine. I didn't notice any performance gain, however it did fix my belt throwing prob.
15 second 1979 f-100 - 302, 3.70's, Powertrax Locker, MSD box, 2300 stall, headers, 4bbl. SOON to be 14 second 79.
I would rather PUSH a Ford than drive a Chevy!
Thread
Thread Starter
Forum
Replies
Last Post