how big of an alt do i need? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

low 84 · 04-22-2003, 12:17 AM

i'm looking at getting one of the magnum alternators in summit thats powder coated black. but the are 80 amp alts. is this enough if it will eventualy be running an air compressor?

gchemist · 04-22-2003, 12:19 AM

I would run at least a 100 amp and higher.

LOHRTBT · 04-22-2003, 01:07 AM

Agree wit G!

79BIG10 · 04-22-2003, 03:33 AM

Ryan you can get a alt from my guy here in Richardson cheap. He carries on hand 100+ amps ready to go.

TX_Mudder · 04-22-2003, 11:02 AM

I got a 100 amp black one-wire alternator from JEGS for 89.95. It looks nice (much nicer than anything else on the engine), is easy to hoop up and keeps my battery charged just fine no matter what I have done so far, including using the winch.
-- Mike

low 84 · 04-22-2003, 01:03 PM

the reason i was looking at this one is because it comes powder coated black. i really don't want a chrome or silver one.

tx_mudder-whats the part number of the one you got? is it 555-10120? is it powder coated black or painted? and is it a glosy finish? thanks man

rockman20 · 04-22-2003, 04:37 PM

One wire alts are nice, but you have to figure a few things into account when using them.

1) They are easy to install. One wire running from alt to battery and you are done.

Bad sides.

1) You usually have to get the engine revved to about 2 grand before the alternator will start charging. (on startup. after it has self energized, then it will charge at an idle)

2) No more idiot light. If you are running a voltmeter, this isn't much of a concern, but if you only have an idiot light, you will never know if your alt dies until you notice dim lights or the truck just stops.

3) One wire alternators are usually more expensive and harder to find.

Now I am not saying they are bad by any means. I am running one on my 69 Cutlass. Went with it because it was the only thing I could find that could pump out 140 amps. Wanted that power to drive the dual electric fans, MSD ignition, headlights, dash lights, stereo, amp, and my other electronics on the car.

100 amp would be the lowest I would go on anything with a computer. On an old engine with no electronics except for the ignition and the stuff in the truck, 80 amp should be fine. My Cutlass was running a 65 Amp, external regulator up until this year and it ran fine. Noticed a dimmer headlight at idle and such, but it did the job.

PHOENIX · 04-23-2003, 01:23 PM

To solve the low output at idle just get an overdrive pulley.
www.rpmoutlet.com $29.95

04-22-2003, 12:17 AM	#1
low 84 Registered User Join Date: Jan 2002 Location: Houston, TX Posts: 2,144	how big of an alt do i need? i'm looking at getting one of the magnum alternators in summit thats powder coated black. but the are 80 amp alts. is this enough if it will eventualy be running an air compressor? __________________ '51 F100, backhalf with a narrowed 9 and coil overs, 18.5" mickeys, monte front clip, +400" sbc in the works '05 1500 Crew Cab RIP '84 swb 5/7 drop, solid cammed 408 w/ fully ported dart heads, th350 w/ 10 inch hughes, 12 bolt w/ 3.73 richmonds and a locker '80 swb 4x4 in progress: 7" lift, 350 th350/np205, d44 and 1.5" ORD tie rod, 14BFF w/discs , armored diff covers, 40" MTR's

04-22-2003, 12:19 AM	#2
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	I would run at least a 100 amp and higher. __________________ Gerardo a.k.a. Mad Chemist Silverado XST videos

04-22-2003, 01:07 AM	#3
LOHRTBT BeWarE tHe eViL CrAnkTOe! Join Date: Oct 2002 Location: Yukon, OK Posts: 3,605	Agree wit G! __________________ ~Dave~ You can call me Mike, Mike Oxlong - 1986 Chevy SWB - Stock for now - *1986 Chevy Custom SWB* *Stolen 6/26/05* - 1985 Chevy SWB SOLD - 1999 T/A Some mods www.cardomain.com/id/ramairdave AIM Screenname - Jester84

04-22-2003, 03:33 AM	#4
79BIG10 I'm back with 2nd truck! Join Date: Feb 2002 Location: Texas Posts: 3,774	Ryan you can get a alt from my guy here in Richardson cheap. He carries on hand 100+ amps ready to go. __________________ 1979 Chevrolet Bonanza Big10 "Tootsie Roll" 1985 Chevrolet Silverado (wife's) Member of the Southern Bowties Club "Don't underestimate how sexy a fat man who drinks to excess can be." Homer Simpson

04-22-2003, 11:02 AM	#5
TX_Mudder Registered User Join Date: Jun 2001 Location: Houston, TX Posts: 126	I got a 100 amp black one-wire alternator from JEGS for 89.95. It looks nice (much nicer than anything else on the engine), is easy to hoop up and keeps my battery charged just fine no matter what I have done so far, including using the winch. -- Mike __________________ http://home.houston.rr.com/chevy73/

04-22-2003, 01:03 PM	#6
low 84 Registered User Join Date: Jan 2002 Location: Houston, TX Posts: 2,144	the reason i was looking at this one is because it comes powder coated black. i really don't want a chrome or silver one. tx_mudder-whats the part number of the one you got? is it 555-10120? is it powder coated black or painted? and is it a glosy finish? thanks man __________________ '51 F100, backhalf with a narrowed 9 and coil overs, 18.5" mickeys, monte front clip, +400" sbc in the works '05 1500 Crew Cab RIP '84 swb 5/7 drop, solid cammed 408 w/ fully ported dart heads, th350 w/ 10 inch hughes, 12 bolt w/ 3.73 richmonds and a locker '80 swb 4x4 in progress: 7" lift, 350 th350/np205, d44 and 1.5" ORD tie rod, 14BFF w/discs , armored diff covers, 40" MTR's

04-22-2003, 04:37 PM	#7
rockman20 "The dude abides" Join Date: Apr 2003 Location: North Dakota Posts: 472	One wire alts are nice, but you have to figure a few things into account when using them. 1) They are easy to install. One wire running from alt to battery and you are done. Bad sides. 1) You usually have to get the engine revved to about 2 grand before the alternator will start charging. (on startup. after it has self energized, then it will charge at an idle) 2) No more idiot light. If you are running a voltmeter, this isn't much of a concern, but if you only have an idiot light, you will never know if your alt dies until you notice dim lights or the truck just stops. 3) One wire alternators are usually more expensive and harder to find. Now I am not saying they are bad by any means. I am running one on my 69 Cutlass. Went with it because it was the only thing I could find that could pump out 140 amps. Wanted that power to drive the dual electric fans, MSD ignition, headlights, dash lights, stereo, amp, and my other electronics on the car. 100 amp would be the lowest I would go on anything with a computer. On an old engine with no electronics except for the ignition and the stuff in the truck, 80 amp should be fine. My Cutlass was running a 65 Amp, external regulator up until this year and it ran fine. Noticed a dimmer headlight at idle and such, but it did the job. __________________ RockMan 1993 Chevy Silverado C3500 1 ton dually 1994 Honda Civic 1969 Oldsmobile Cutlass S 1953 IH Farmall Super M New to the fleet: 1992 Subaru Loyal

04-23-2003, 01:23 PM	#8
PHOENIX Registered User Join Date: Oct 2002 Location: Phoenix, Arizona Posts: 4,703	To solve the low output at idle just get an overdrive pulley. www.rpmoutlet.com $29.95 __________________ * AVOID: LOPER'S PERMORANCE / LOPERSPEED.COM OF PHOENIX, AZ & COTTMAN TRANSMISSION *

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