Then you've never had a 10DN alternator (GM) with an external regulator. When I first got my old 327 Chevelle, it had that alternator, and when idling at 600-700 in drive, the battery would drain to under 12.5vdc consistently.

I would put it in neutral and rev it 'til the alternator would kick in, but that was my temporary solution. I moved up to a 105 amp one wire alternator, which worked fine until I got serious about drag-racing, went to a big-block 427, and used a 140 amp alternator (with deep-groove pulleys).

But, after continually throwing belts at 7200+ rpm (and disintegrating a rod at 7400 rpm when the limiter failed), I switched to a bigger/badder 427 with dual batteries and charging between rounds. No more alternator problems. P.S. that 14:1 compression BBC would rev all day to 7200, and still lives after 100's (1,000's?) of rounds (but now traded for my X5). Sniff!

__________________
01 BMW X5 E53,3.0i-5L40E, 7/13/01
topas-blau,Leder-grau,"resto-project car"

Here:
14 Lexus ES350,3.5L-U660E
09 HHR Panel,2.2L-4T45E
04 Chevy 2500HD,6.0L-4L80E
98 GMC Sierra 1500,5.7L-4L60E

Gone:
66 Chevelle Malibu 2dr ht.,327>441c.i.-TH350>PGlide/transbrake
08 Cobalt Coupe,2.2L-4T45E
69 & 75 C10s,350c.i.-TH350
86 S10,2.8L-700R4
73 Volvo 142,2.0L-MT4
72 & 73 VW SuperBeetles,1.6l-MT4
64 VW,1.2l-MT4
67 Dodge Monaco 500 2dr ht.,383c.i.-A727
56 Chevy 210 4dr,265c.i.-PGlide