<VV> Do Gen Pulleys Lose Their Grip?
Thu, 20 May 2004 17:06:08 -0700
>At 1439 05/19/2004 -0400, firstname.lastname@example.org wrote:
>>I have a modern (7127) alternator installed on an early with a custom
>bracket. It uses the original generator pulley. The system works fine until
>you put a really, really heavy load on the alternator (AC with condenser fan),
>then the voltage starts dropping.
>Not entirely unexpected. What *is* the rating on your alternator? And how
>much does the voltage drop?
>>An alternator rebuilder, whom I know and trust, says the unit checks out
>fine. (I had replaced the diodes, regulator, and brushes in
>He says the belt is probably losing grip.
>Do you hear any shrieking or chirping noises? One way is to simply watch the
>alternator with the engine running with a heavy load while you rev the
>engine. However, it's gonna have to be slipping a LOT to drop the voltage
>enough to become an issue.
>>When you look at it, on a Corvair the belt only grips the gen/alt and idler
>pulley over about 1/4 of the pulleys' circumference. Unlike on other engines,
>where the belt contacts about 2/3 of the pulley.
>However, a lot of people have been running standard alternators with AC and
>other accys all on at the same time and no real problems.
>>Any thoughts on what might be done to improve the grip? I have tried
>tightening the belt, using a "cogged" belt, and loosening the belt, to no
>It's been my experience that the belt needs to be relatively loose in order to
>stay on the engine unless you never rev the engine to any degree... better
>luck is had with Powerglide cars than manual shift cars.
>I'd work with a smooth polish on the pulley and use a cut belt... IF the
>alternator pulley is actually slipping. The standard cut belts will bulge
>slightly when pulled around a corner and grip the pulley tighter. A cogged
>belt will not. The cut belt on a polished pulley is gonna give you the
>tightest grip you can expect without excessive belt wear.
>I'd also check out the wiring, especially the heavy wire from the
>the battery + terminal. If that wire has a less than adequate connection on
>either end, voltage drops could become evident, along with hot connections.
>There are sharper people in here than me, who likely will have better
>information for you but this is what I've seen in my times.
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