How much HP will I get out of Mac Underdrive Pullys
 

I'm about to buy MAC Underdrive Pullys and I was wanting to know how much HP I would get after the install?

Probably around 5 rwhp...

What about at the Fly Wheel?

In general,
A stang with a 5 speed manual transmission will suffer about a 15% drivetrain loss before the power gets to the wheels...

so, maybe about 7 hp?

mac power pulleys
 

I have a set of the mac power pulleys on my 97 stang gt !! It was a good mod and for the cost not a bad mod ! But the aftermarket people that state this and that about the horses you will gain from there mods are lies , I take what ever they say ( like 15 horse gain ) and cut it in half , so you will see like 5 to 7 rwhp maybe !! The more mods that you do the better everything gets !!!

If I were you I would go with the Steeda pullies because they have a new balancer built into the crank pully instead of having to try to reuse the stock one.

They are the same size as steeda's under drive pulleys. So according to MM&FF, you will get 3 HP, 12 lbs-ft torque.