The Stovebolt Site Forums The Shop Area The Electrical Bay Higher Amperage Alternator Advice Wanted

Hi All,

I'm thinking with my 350/350TH conversion with an HEI, that i need an alternator that puts out more amperage.

It currently puts out 48 Amps (i was told by local parts store).

Also, my truck has problems starting sometimes--lots of history behind this. I put a new battery in and my truck started RIGHT up--no problems. Now, after a month or so has passed, if i dont start my truck on the first try, i need a jump to get it started.


Anyways, if I put a higher amperage alternator in, what rewiring do i have to perform? My truck has basically, the original stock wiring.

I seem to remember that the guy at the local parts store told me that there is a chevy alternator that puts out 80 Amps--as opposed to my current (no pun intended) 48 Amps.

Your advice would be appreciated.


Thanks,


Tom

Tom........

As long as your truck is already running an alternator.......a change to an 80 amp unit will not require any changes at all.

Make sure you find one with similar plugs/orientation.
Just bolt it in and watch your starting woes, dim lights and ignition problems dissappear!

48 amps is really pretty small for running a truck with anything electrical fitted to it.....let alone charge the battery as well!
All the best............Doc Bob

The capacity of the alternator won't help your starting problems, unless the battery is chronically undercharged for some reason. A 48 amp unit will keep the battery charged OK unless you've got a lot of high-draw accessories like a high-wattage sound system that's running wide open all the time, or a lot of accessory driving lights, etc.

An alternator supplies the current required to run the ignition, air conditioning, fuel injection, fuel pump, etc. before it uses the leftover capacity to recharge the battrery. The only reason to have all that alternator capacity is to feed a lot of greedy accessories. 12 volt generators with a 25 amp output used to keep a battery charged, but there wer not many accessories to feed. It sounds like you've got a sulfated battery, not a lack of alternator capacity.

A battery that sits for long periods of time without being exercised loses a lot of cranking power, and it will only be good for one attempt at starting. Have somebody do a high-load current test on the battery. I'll bet it fails!
Jerry

My guess would be your battery has a cell that is going dead. I would suggest replacing it and I bet you will solve that problem. You can get a higher amp Delco that will replace your current alternator. I can build one in whatever amperage range you like in the 70-100 amp range in a one wire unit that is really nice. Does away with some of the wiring, you just need it to make a path to the guage and then to the battery. Private message me if you want more info on this.
Ken

48 amps is rather small, but you probably have other problems. Leece Neville makes a 1 wire 160 amp alternator that we used successfully for many years on our over the road trucks. Our newer ones now use a pad mount. The old are small enough to put any where and they are reasonable. 150 at a truck dealer and sometimes around 75 on eBay. We call them 1 wire but they are actually 2 so polarity can be reversed. We run a 6 gauge wire to the starter lug and another to a ground on the engine. No other wiring modifications are necessary.

I'm with Jerry on this, sounds like a sulfated battery.
How many other accessories are you running? I've got a Mallory ignition w/Promaster coil & a 3RLi spark box, electric fan, fog lamps, H-4 hi output headlamps, DeLuxe heater, and about 450 watts of stereo, all runing on a 65 amp alterator. I don't think I've ever seen the amp gauge (afteramrket Autometer, no the original) go any futher that 30 amps with a full load on it. Unless you're running an extremely high power stereo or a snowplow, I don't really think you would need much more than 60-65 amps.

AAAaahhh-but it's pretty hard to have too much of an alternator. Remember-If a lot is good,then more is better,and too much is just about right! ;)That's the American hot rodder's credo.
Speed

I think you can have too much alt. output. You have to have enough belt system to turn it under load. This little skinny belt drives the water pump & fan also. It will slip & squeal with a high amp. alt. 65 amps is enough for most trucks unless you are running A/c & electric fan. Then you may want 85-95 amps. mainly for the more output at idle & low speeds.

re-read longbox & HRL
change to a 2.0 gauge wire w/ good ends to the engine starter.
make sure a good ground is there, eng to frame, cab to frame & eng to tranny.
coat everything w/ a battery coat so corrosion can't start.
a 48 amp should work just fine to charge your battery
or
change to a 10 or maybe 12si alternator. DO A THREE wire system.
http://www.madelectrical.com/electricaltech/delcoremy.shtml
http://www.madelectrical.com/electricaltech/onewire-threewire.shtml

my .02