Originally Posted by SpinMonster

On my C5 with head/cam ect and yes UD pulley, 900rpm idle, the station attendant said it was the cleanest running car he ever tested w/sniffer.

Understand that the UD pulley can come with an OD pulley for the alternator so no added idle speed is needed ( I have installed them for cars with the stock idle and no OD alternator pulley without issue). Why are you so insistant on finding something not right? Sometimes in life you win.

Its a gift mod.

One more fact. When you do this mod it is usually in addition to a cam swap and no cam that makes any real change in power can use the stock idle rpm. Its a tech section and people come here to discuss mods and ultimately do them. The ones that stand the test of time and 1000's of installs are worth doing and I dont know anyone that skipped this mod when doing a cam. I see no one complaining about not passing emissions, voltage, current, ect. One more thing. When you get an emissions test done, it isnt at idle rpm.

I have never seen a single person remove one for it having a downside. If you had a stock idle, automaic trans, and had dimming due to huge stereo amps being drawn, you get an OD pulley for the alternator and its done.

Originally Posted by SpinMonster

If you raise the idle of the car the alternator is spinning as fast as it was with the stock pulley at the slower idle rpm so no there is no difference between the old and new amperage. Further, if you use an overdrive pulley on the alternator and an underdrive pulley on the crank there is no amperage difference. Not sure why you posted here but just for UD pulley facts: My cousin's 2002 trans am still has the original battery in it. He has an UD pulley on it since 8k miles when I installed it and it now has 112k miles. No issues to this day with any dimming or electrical issues. No there is no downside to a pulley swap. I think GM should use it as stock. But, I do have a theory! I think since they use the same pulley on so many vehicles that may have an issue with the power, its possible that using the same one on the corvette keeps costs down.

Why dont they grind the cam with 208 on the intake side?
Why not mold the TB with the same shape as a ported one?
Why dont they put in a 160 thermostat?
Why do they release the car running so rich from the factory?
Why do they use a restrictive air filter?
Why do they have the air cleaner draw hot air instead of a cool air duct through the shroud?

They have to stop somewhere.

Originally Posted by Mike Villareale

That being said, do recommend just the underdrive pulley & skip the ovedrive on the alternator. As discussed, I will be swapping the cam, so w/ retune for all the mods the idle will but moved up so as you mentioned compensate for the pulley?