Alternator, how amny AMPS?

[Myles]

Hi guys, need to know what alt is ok for new build. 12sec Drag only car on trailer.

81 Malibu 355sbc 9.5:1 holley carb full mechanical no choke. All acc. Will be in toggles with fuses.

-elec fan 19amps
-elec water 6amps
-stock hei ign & 4 equuis gauges
-electric window (seldom)

New battery 1000 / 895 cold cranks

No power brakes
No head light use
No radio
No heater

Worse case I dont see the car totaling more than a 40amp draw at once, ever.

Local auto parts new alt 63AMP for 81$

Everyrhing else is much more expensive and some guys say no point in having 100+amp alt for this build.

Please let me know your thoughts,
thanks

 

[fleming442]

If it'll never see the street, you don't need one at all (generator and battery charger at the trailer).
Check to see if that 63a is external or internal regulated. I would say go for the 100a if you can. Reason being that the car won't see much run time, and you'll want as much recharge in that short amount of time as you can get. Or, take your generator and charger.....

 

[bracketchev1221]

I had 100 amp on mine. Point being like was said above, you will have the fan on with the car sitting and not charging it. But you do want an alternator because the ignition works better at 14.5 volts than at 12 or less. But here is a little tip I used. I would start the car at the end of the staging lanes and turn everything on. Do the burnout with everything on and then roll up to stage. Just before I lit the prestage bulb, I would reach up and turn the fan off and then roll in. Once I went through the finish line, I reached up and turned the fan back on for the ride back to the trailer. This was on an 8.80 car making 980 hp. The car had an alternator, and a 160 thermostat.

 

[Myles]

thanks guys,

my other 12 sec Malibu is all the same, minus the electric water pump. the 63 amp has been fine, i only run fan near the end of the day if the rounds are getting closer together. no generator or charger, however i have the bat on a charger the night before i race, thats it.

do the 100+ amp alternators cost significant power to run, verses the 63? and yes i also turn my fan off when i pre stage.

many guys have charging issues when the final rounds get close together when they have no alternator.

 

[bracketchev1221]

I tried initially putting the alternator on a toggle switch to kill the field when I staged. The car went no faster with it on or off. So I removed the switch and went to a 1 wire alternator that was just on.

 

[lilbowtie]

What ever you put on it will be a plus - the 100 amp alternator will pull more power only if it's pulling more amps than the 63. My Sonoma runs w/o an alternator and doesn't take much in between rounds to get fully charged, but working on installing a mini that will work with the engine plate. I'm going to suggest getting a single wire alternator for your situation. A low mount bracket works good with the electric pump. Watch your pulleys so your not spinning the crap out of it.

 

[bracketchev1221]

Look at Alan Grove for the brackets.

 

[Myles]

Thanks guys, and nice truck.
Sharp in white.

Stock pulleys I assume are ok ? Shift and trap around 6400.

I dont have much room, I now might be running power steering, new Holley fuel mechanical fuel pump on other side..

 

[Streetbu]

You also need to remember that the fans pull 19 amps when they are on. The alternator doesn't charge at 63 amps at idle though...