jwillman

Doing the AC Delco upgrade this weekend and have an overdrive pulley. Goal is to eliminate the low voltage at idle situation I have with the dual electric fans and AC running.

Any long term experience with the over drive pulley installed?

928mac

I would like to decrease the crank pulley by 3/4 an inch and solve alt, steering and ac low RPM problems

Alan

Err - you'd be going in the wrong direction...

Alan

Alan

You risk easier belt slippage and you should check the max alternator RPM at max engine RPM via the new ratio.

Alan

FBIII

Smaller pulley results in the alternator spinning faster at any given rpm therefore higher output at lower engine rpm's. He is not looking to do the old hot rod hp saving trick of running a larger pulley to slow the alternator down.

medipedicman

I think that Alan was advising correctly on the diameter of the CRANK pulley.

Correct for the pulley on the alternator...NOT the crank.

jwillman

Anyone tried the Powermaster overdrive pulley on the Bosch Alternator?

Mrmerlin

please post a picture of the pulleys your thinking of swapping.

NOTE there will be a pulley diameter that will bee too small for the belt to grip properly when the alternator has a very high load.
In other words the belt will slip even though you have made the belt tight.

NOTE damage to the main bearing can result from over tightening the belts,
this damage will occur when the engine is started since no oil pressure is available

GlenL

What's the voltage at the jump post when idling?

jwillman

So the belt I had was a bit looser than I image based on the constant recommendation to be "tight" and tensioner was at max so I went to the next smaller belt.

How tight is tight enough without risking bearing damage?

dr bob

The tension on the belt isn't related to pulley size, except when there's a temptation to put too much tension on the belt when trying to solve a slippage problem with a pulley that doesn't have enough contact with the belt. I use a rule of thumb, with moderate thumb pressure in the middle of the span giving a deflection equal to half the thickness of the belt. That makes the ribbed alternator belt pretty darn tight.

For those playing along at home, ribbed belt tension and slippage are somewhat counter-intuitive. First, you don't get much if any noise from a ribbed belt that's slipping. Second, a ribbed belt may slip more at idle than at speed.

I would wager a beer that many of us who suffer from low idle charging could replace the alternator belt, set the tension correctly, retension after a few hundred miles, and find a lot of those idle charging symptoms would mysteriously go away.

Caveat: I don't drink cheap beer, but you do...

jeff spahn

I'll wager a beer with you. Granted, I don't have any charging issues at 13.4 V at idle w.Ac, lights and defroster on but I'll still wager a beer with you. Holy Ale (tempered with burning witches) works for me. That or a good bottle of Vintage Ale.

dr bob

It's a sucker bet, with some vague reference to "many of us who suffer". But I'll swap beers with you anytime. I'm cheap and don't drink enough beer to have a favorite. "Cold" and "wet" are primary criteria. Turns out I'm a cominsuer of beer.