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Discussion Starter · #1 ·
Looking for a suggestion on which alternator to install on my 350, be it an 80, 100, or 140 amp. Any suggestion will be greatly appreciated. Thanks. Ted
 

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Trifive Automotive Electrical Wiring Expert
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There's other considerations, bigger is not necessairly better. If you have stock wiring, do NOT install a 140 amp alternator without upgrading the wiring. You must have a heavier wire from the alternator, directly to the battery or starter. A 63 or 80 amp is plenty large enough without electric cooling fans. A 140 amp alternator can burn down a stock wired car, especially a 55 or 56, since the charge wire runs inside the car before it goes back through the firewall to the battery, in the event of a almost dead battery. Beside, a battery should never be charged at that high current under any conditions.
 

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OK.. I see... I was going to ask you to clarify that but I see you said this

since the charge wire runs inside the car before it goes back through the firewall to the battery, in the event of a almost dead battery.
So only if the battery is very low will that much current ever go through in a 55 or 56. I didn't think about that because my 57 goes to the battery.

To bypass that you can just run a lager gauge wire from the ALT right to the battery and not have it run in the car first. Everything else will be fine if you have the correct size fuses installed.
 

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Trifive Automotive Electrical Wiring Expert
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Discussion Starter · #10 ·
Not a problem as long as the wiring is up to the task. :tu
After reading these responses I became concerned and contacted Summit via email to see if I can change my order from the 140 amp to the 100 amp alternator. I hope the 100 will be more than enough. Thanks. Ted
 

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After reading these responses I became concerned and contacted Summit via email to see if I can change my order from the 140 amp to the 100 amp alternator. I hope the 100 will be more than enough. Thanks. Ted
Probably a good move....Don will not lead you astray.
 
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I do a lot of ignition system conversion work, and recommend alternators for those conversions. That said, I have over 600 old, wrecking yard 12SI alternators running around on all sorts of different makes/models of automobiles, boats, fork lifts, name it.

ALL of those alternators came off Chevy Citation and their clones, all 12SI, 94 ampere, converted with just one jumper wire on the outside of the alternator, to "single wire" use, with only one failure, a diode went on one of my own units.

All of these were wrecking yard units, literally taken apart, cleaned, reassembled, installed, and run. About 10 percent of them required a simple, low cost rebuild kit, the rest, just cleaned up and run.

I do not, for any reason, run the CS series GM alternators, too much failure, problems, they just tear themselves apart. The factory CS alternator, and ALL subsequent replacements, on my 1986 GMC Safari van, died gruesome deaths. I finally got so irritated at those CS alt failures, I retrofitted a 12SI 94 amp Citation alt, some 12 years ago, NO problems since then. Sure is better than a CS alternator failing every 6 months or so.

It is also nicer to pay only 15 bucks at a wrecking yard, and use a little effort to redo an SI alt, ONE TIME, vs 100 bucks EVERY 6 months for a useless, failure imminent CS alt replacement.

Just my 40 plus years of hands on experiences.
 

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After reading these responses I became concerned and contacted Summit via email to see if I can change my order from the 140 amp to the 100 amp alternator. I hope the 100 will be more than enough. Thanks. Ted
the aftermarket wiring kit that you bought... is it a stock replacement or will it run from the alt to the battery? did you every say what your car was?
 

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Alternator info

I do a lot of ignition system conversion work, and recommend alternators for those conversions. That said, I have over 600 old, wrecking yard 12SI alternators running around on all sorts of different makes/models of automobiles, boats, fork lifts, name it.

ALL of those alternators came off Chevy Citation and their clones, all 12SI, 94 ampere, converted with just one jumper wire on the outside of the alternator, to "single wire" use, with only one failure, a diode went on one of my own units.

All of these were wrecking yard units, literally taken apart, cleaned, reassembled, installed, and run. About 10 percent of them required a simple, low cost rebuild kit, the rest, just cleaned up and run.

I do not, for any reason, run the CS series GM alternators, too much failure, problems, they just tear themselves apart. The factory CS alternator, and ALL subsequent replacements, on my 1986 GMC Safari van, died gruesome deaths. I finally got so irritated at those CS alt failures, I retrofitted a 12SI 94 amp Citation alt, some 12 years ago, NO problems since then. Sure is better than a CS alternator failing every 6 months or so.

It is also nicer to pay only 15 bucks at a wrecking yard, and use a little effort to redo an SI alt, ONE TIME, vs 100 bucks EVERY 6 months for a useless, failure imminent CS alt replacement.

Just my 40 plus years of hands on experiences.
Makes sense. I filed this info, Thanks Mike.
 

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Discussion Starter · #17 ·
I have a 55' hardtop. Years ago I bought a complete wiring kit for a 55' chevy pickup that I was working on, but sold the truck with out the wiring. I paid something like $450 for it, and it's still in the box. It was designed for the 55-59 chevy pickups, but I plan to install it in my hardtop. It is a complete harness with extra wires for a power seat, power windows and etc; also has a 10 circuit fuse panel that takes the stab in type fuses. I contacted Summit but it was too late, they had already shipped; which they are good at = fast shipping. I plan on returning the 140 amp alternator and go with either an 80 or 100 amp. My question now is what is a CS alternator, and are the alternators that Summit sells CS? Don, if you're reading this, should I go with the 80? Thanks for all of the input. Ted
 

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The amperage of the alternator won't matter if you do two things. (Above 80 is probably overkill though)
1. Make sure you have a heavy wire that goes from your alt directly to your battery. (to stop the issue Don talked about with a dead battery)
2. use the correct fuse values

The only way anything bad will happen (fire) is if you pull to much current. That will only happen if you splice into a line before the fuse box and have a bunch of stuff hooked to it (that would be the same way a Christmas tree catches on fire) or your fuse does not blow and what ever short you had does not stop.

An alternator does no push current (amps) and you'll only use what you need. If that wasn't the case, your TV would blow up each time you turn it on from too many amps. You can burn your car down just as easily with no alternator and just your battery, so it really comes down to things being hooked up correctly and not the rating of the alternator. In the case of a 55-56... that one wire from the alt to the battery will make a huge difference in safety with any alternator over 30 amps.
:anim_25:
 

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100 is what I ordered for my project and it will have the fans a good stereo, etc. and it will have a heavy wire from the Alt. to the battery.
Hope you are happy with yours, it will look great.
Larry From Tulare, CA
 
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