[ho428]

68 Bird, street car, 433 4 speed, MSD 6AL box, blaster coil, pro billet. Single fan on the cold case radiator, powermaster starter, no big stereo amps or other add ons.
Everything is still set up for 3 wire with OEM style but solid state replacement voltage regulator, but I need a new alternator. What amperage? Will the voltage reg need changed if I go with a 100 amp?
Also getting an Optima Red top 800 amp battery.

[Lee]

100 amp should be fine for your application. Make sure the charge wire is sized properly - http://www.powermastermotorsports.co...e_wires_a.html I'd go ahead and convert to an internal regulator.

I've never been impressed with the Optimas that I've used. I've had a few XS Power and a Braille, however, and will be sticking to those. Smaller, lighter, and more powerful. The CCA rating on these AGM batteries is VERY misleading, a 500cca AGM will outperform a 1,000cca lead-acid in my experiences.

[FrankieT/A]

I use a CS130 alternator...105 amp and charges at an idle(bright lights at idle). It is a direct bolt on except for the plug which is easily changed of course it is internally regulated.. If you are looking for an application...use one for a 1990 corvette. You may have to reclock it for your app. My car is fully loaded with A/C, and power everything. As for the Optima battery(Red), I've been using one for about 9 years that I personally killed flat three times in that period by leaving my dome light on for days. I've charged back up according to Optima recommendations each time and it has come back each time. It never labors while cranking even hot(10.5:1 455). I have nothing bad to say about Optimas. Mine doesn't owe me a thing...

[ho428]

Originally Posted by Lee

100 amp should be fine for your application. Make sure the charge wire is sized properly - http://www.powermastermotorsports.co...e_wires_a.html I'd go ahead and convert to an internal regulator.

Not real sure how to go about switching to a single wire alternator, so much goes through the main harness to the regulator and horn relay on the Radiator support.
The MSD instructions gives me a diode to install at the Regulator but I'm replacing it with a Solid State one which I think solves the run on issue.

[Bill Hanlon]

Internal regulator doesn't necessarily mean single wire. You may have to re-route the sense and indicator wires. I'd recommend against single wire.

[FrankieT/A]

Originally Posted by Bill Hanlon

Internal regulator doesn't necessarily mean single wire. You may have to re-route the sense and indicator wires. I'd recommend against single wire.

I second this...I would not use a "one wire" set up.

[george kujanski]

You need to be careful about the output ratings on some alternators...some aftermarket units in a 10DN (external regulator) or 10SI(internal regulator) case may be "rated' at 100 A, but that rating is at a shaft speed of 5000RPM, (about 1500-2000 engine) meaning it's output near idle is lower and may not charge the batt with the fan on.

A Delco 12SI or later Delco CS130 would be a better choice due to h1gher output at idle. One version I have seen is a 12SI from mid-80's Camaro rated at 94A. and it'll do about 50 A near idle.

George

[Lee]

Originally Posted by Bill Hanlon

Internal regulator doesn't necessarily mean single wire. You may have to re-route the sense and indicator wires. I'd recommend against single wire.

Correct! I do not do 1-wire conversions. Most of the PowerMaster alternators can be wired as 1-wire or 3 wire, you just have to pop out the plug.

I bought a "100 amp" PowerMaster 12Si earlier this year. I came with a dyno tag, signed by the person doing the test. That tag showed it put out 90-something amps at idle, and somewhere around 106amps at higher rpm.

[ho428]

Originally Posted by Lee

Correct! I do not do 1-wire conversions. Most of the PowerMaster alternators can be wired as 1-wire or 3 wire, you just have to pop out the plug.

I bought a "100 amp" PowerMaster 12Si earlier this year. I came with a dyno tag, signed by the person doing the test. That tag showed it put out 90-something amps at idle, and somewhere around 106amps at higher rpm.

Problem I'm finding with the pop out the plug is they look to have the later style GM blade plug, mine has the more square end on the two wires. Don't really want to splice in a new plug onto a brand new MH harness.

I don't know the nuances of model and frame style on these things.

[HWYSTR455]

Hm. So you're considering using an internally regulated alt with an external regulator still in place? Won't that cook the external regulator? Or the alt? Won't the regulator in the alt peg output since the external is handling the sensing?

It's fairly easy to convert to an internal regulator, and it would be easy to rewrap the harness.

One reference with pics:

https://67-72chevytrucks.com/vboard/...d.php?t=119379

Search and ye shall find many other examples.

Yes, PowerMaster does provide a 'dyno sheet' listing output, but a George pointed out, that's based on shaft speed of the alt. Shaft speed is controlled by the engine pulleys along with the alt pulley, so you can't take what's on the sheet without accounting for 'actual' shaft speed with your setup.

As for voltage sensing, and the buss at the horn relay, take a look at MAD Electrical tech docs:

http://www.madelectrical.com/electri...esensing.shtml

http://www.madelectrical.com/electri...evymain1.shtml

Contents page:

http://www.madelectrical.com/electrical-tech.shtml

For your case, that PowerMaster 12si will be perfect. And yes, they go both 1 & 3 wire.

EDIT: You can pop the terminals out of the old alt plug on the harness, crimp new 56 type terminals on, and plug them into the new connector.


.

[HWYSTR455]

Dorman replacement GM SI alt plug: ($3.00)

https://www.autozone.com/electrical-...ector/600718_0

Packard/Delphi 56 Terminals at Del City (can source other places too)

https://www.delcity.net/store/Packar...rminals/p_9291

You can get a cheapie open barrel terminal crimper, but everyone should have a good ratcheting crimper that has multiple jaws for different types on terminals. At some point, you will want to use at least weatherpak connectors. Try to find one that already has the multiple bits with it.


Klein 1006 closed barrel crimpers are excellent, industry standard, and not expensive.

https://www.homedepot.com/p/Klein-To...1006/203433805

Just use shrink tube over it, and never buy the barrel connectors with the cover. I like the nickel high temp barrel connectors.

.

[HWYSTR455]

Before someone goes into the crimp vs solder debate, do some homework:

https://millennialdiyer.com/articles...imp-or-solder/

.

[ho428]

I guess what I don't get about the alts that will go 1 and 3 wire is I thought the 3 was not internally regulated so I could keep everything OEM appearing, while the single wire was internally regulated. On Summits site I see listings for the single wire, 3 wire, and 1 and 3.
I run a single wire on the race car, very simple system with harness I made, but on this restoration I'd like to keep it OEM but I need more amps than the (I think) 70 amps, that came from the original.

Saw a new polished 100 amp at a swap meet a few weeks ago with the correct plug, knew I should have bought it then but I've not had good luck with swap meet electrical parts.

[george kujanski]

Another thing to remember, just to confuse the issue, is that published ratings by some mfgr's may list the initial output values in a quick test. Properly done, the ratings should reflect the output available with the alternator hot and stabilized such as in underhood temperatures. Outputs are lower when hot and stabilized.

Delco publications reflect real world conditions, as did ours, when I was in the biz.

george

[64speed]

You can get an adapter from M&H that will plug your square plug into the rectangular plug of a more modern alternator and it comes with a cap for the voltage regulator wires in case you want to go back to that too

[AG]

I changed my brother's '70 LeMans to a 12si and got the different 2 wire plug, the other mod is attaching leads across the plug that used to plug into the external voltage regulator. On my race car, I have a total load of 70 amps and use a 6 gauge wire that goes to the trunk battery and use a 12si rated at 100 amps. Works great.