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Old 02-08-2005, 11:12 AM
blndweasel's Avatar
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Care to guess?

Hey everyone,

It's been a long time, but I'm in need of your opinions.

I am about to get rolling on my project wiring, and need to try and decide what size alternator to install. Let me try and give you a detailed breakdown of the components, with some draw estimates...

chevy 350:
HEI Dist with Pertronix coil draw: ??
SPAL dual fans: draw: est 25 AMP
Moroso water pump: draw: est 7 AMP
Headlights (Halogen): ??
Fog lamps (H2 Halogen): ??

For the most part, I'll be driving during the day so I'm guessing all I need to account for is the coil, the fans, and the water pump. But it would be nice to know whether I could drive during the day with my headlights on while still charging the battery.

If anyone can contribute knowledge relating to the average AMP draw of a typical HEI setup, I would greatly appreciate it.

I currently have a 60 amp stock alternator, which I have used in the past and could not overcome the load, as well as a 105 amp powermaster alternator which seemed to work for a while but I was having so many electrical problems (old harness, bad electric fan motors) that i couldn't tell if it was big enough or not.

I am fully replacing the wiring harness, and all other components, so I'm guessing things will be a lot cleaner with the new setup. My intuition tells me to try it with the 105 amp unit, and if i'm still having problems, to wait until that point to purchase a new unit.

In fact, just by having written this down, I think I've decided that's what I'll do. I'd still appreciate any input on HEI charge load in a typical setup though.

Thanks in advance for any help or insight you can offer! T minus two months to launch!! (it's been two years since my poor ride has left the garage)


the blonde weasel

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Old 02-09-2005, 02:42 PM's Avatar Moderator
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I can't imagine a 105 amp alternator not keeping up. I would go with it.
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Old 02-10-2005, 01:48 PM

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Did you omit the windshield wiper motor, electric fuel pump and heat/air blower motor on purpose or do you not have them? Motors = big amp draw (relatively). The electric water pump at 7 amps sounds low, but every one I have seen has fine print that does not recommend for street driving. If you have air, current is required to keep the compressor clutch engaged.

As Willys said, 105 amps should cover you. When you get into power seats, windows, butt warmers, electric defoggers, BIG sound systems, door poppers, EFI, electric air compressors and hydraulic pumps, you better think BIG.

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