Did a quick search for this. Seems like a neat way to get more idle juice out of the alternator. Didn't find any for sale. Do these exist?

When I had my TPI, I bought the March "Power and Amp" series. the crank was underdrive, but the alternator was an overdrive. I think March sells the smaller alternator pulley separately

https://www.summitracing.com/parts/mch-112

This is the whole kit
https://marchperformance.com/aluminu...-kit-3494.html

Ebay has them for $20, have one on my car. Works great with my 250A alternator.

Thanks. $250! I'll check eBay... :-)

heat seeker do you have a link or part number for a stock LB9?

It's 250 amps, not dollars. lol

No prob!

Hah. That was the March pulley set.

Does this look right?

https://www.ebay.com/itm/Delco-17Si-27Si-CS121-Alternator-6-Groove-Overdrive-Pulley-Increase-Amp-At-Idle/192037293405?hash=item2cb6508d5d:g:HpAAAOSwgQ9VidIb:sc:USPSFirstClass!91206!US!-1:rk:1f:1&frcectupt=true

Yep sure does.

https://www.ebay.com/itm/POWERMAXUSA...frcectupt=true

I bought this one. It's slightly smaller, but not by much. Mine is the CS130 alternator style....shaft should be the same size.

I would just upgrade to an AD244 alternator. Very easy and inexpensive upgrade.

gets you 130 amps at idle.

https://www.thirdgen.org/forums/electronics/755380-ad244-conversion-took-plunge.html

I use a pulley from a fox body mustang, its a bit smaller than the factory one.

Using a slightly smaller alternator pulley works. But need to keep the RPM down. Otherwise can wreck the alternator.

RBob.

all the more reason to just upgrade to an alternator that's designed to put out the higher amperage at lower rpm, like the AD244.

I keep it under 8000rpm all good

Thanks for the help. Works GREAT! Needed one size smaller belt. My belt was already on the ragged edge of too long. Volts stay nice and strong at idle and it powers the 60A of audio without a hiccup.