SC belt length with 2.7`` pulley

Good day!
Just installed 2.7 SC pulley instead of 2.85 stock.
I hear whistling sound because of slack belt. I don`t know know original length exactly, probably 1463mm. It`s difficult to take it off and measure. Anybody knows what lenght should I use with 2.7 SC pulley?

.15" is not a much of a difference in size. the tensionser should take up the slack unless it is at the max position.
what most of us do with the S2 motor is just upgrade the tensioner pulley size from 3" to 3.5". and that is for a .4"+ pulley drop.

I have to ask since you dont have it in your sig, but what are your supporting mods with the 2.7?

Also, if you do actually have slack in the belt to the point that is it slipping at WOT then you may need a new tensioner, not a smaller belt or larger idler.

If this is on the series one, (which the stock is 2.85), then your stock belt is fine(if its new). I run stock belt size and tensioner on a 2.5"

Also FYI, the series one is a breeze to change to a new belt. None of that removing engine mounts like the series 2.

it`s all right at WOT. I hear whistling sound when idling. May be tensioner isn`t very good.

95 SC Riviera, AL-104 plugs and 95 octane gas for today. 180 t-stat, FWI and catalytic converter cut soon.

Before installing 2.7 pulley I measured KR by Tech 1, it displaed "YES" and figures up to "14" on WOT. But I don`t remember, are theese figures KR level or timing adjustment. Also I had "Weak 2nd cylinder" error at that time. Fixed now and I hope KR reduced too.