team39763

iTrader: (3)

I read on another forum that ATI doesn't recommend using a 25% underdrive pulley with a high hp motor. I hadn't heard of that before, but wanted to ask if anybody here has had a problem. I think they mentioned that it doesn't handle the harmonics well with big power. A friend of mine has an underdrive pulley on his sprayed 5.3L, but he hasn't run it yet. I'd appreciate some info or insight.

427

iTrader: (3)

The inertia ring is smaller on the underdrive, so the ability to do the work goes down. The full size ATI will do its job better on high hp engines. You should also use the softer durometer rings in a high hp engine and change them every couple of years.

Kurt

team39763

iTrader: (3)

At what point(as far as HP) does this become a factor? Is there a rpm limit? Does the SFI approval make a difference or not?

team39763

iTrader: (3)

What does SFI's 8.1 approval mean anyway?
EDIT: Meant 18.1

JL ws-6

iTrader: (50)

The SFI rating, means that it was tested for it's intended use and passes the required testing.

You can read more here: http://www.sfifoundation.com/