Previous Thread
Next Thread
Print Thread
Anyone using a GM 10si or 12si alternator on a SB? #205516
01/26/09 10:31 PM
01/26/09 10:31 PM
Joined: Jan 2003
Posts: 1,482
Lake Orion, MI
goldduster318 Offline OP
pro stock
goldduster318  Offline OP
pro stock

Joined: Jan 2003
Posts: 1,482
Lake Orion, MI
After attempting to mock up my siezed '89 denso alternator I had from the 318 I bought 5 years ago (it was seized then) and finding that its hard up against the heads on my 360 with magnum heads. The ~60 amp round back alternator I have just doesn't cut it...its bad at idle. I have the amp gauge bypass completed and I get roughly 11.5v at the dash at low idle with the lights on and the engine running. It gets 14.5 when the engine is above idle, so the car seems to have decent wiring now.

I got to thinking that using a GM 12si alternator might be the hot ticket. They are pretty slim (case without the pulleys and fan is 4.84")



they are cheap and also easy to take apart and rebuild yourself. You can also get tons of these in upgraded versions or even brand new from several sources. I would use the 94 amp unit which has a curve as follows:


Keeping in mind that that's alternator RPM and I'd likely have a 3:1 ratio...so at an 800rpm idle, the alternator would spin at 2400rpm...giving about 64 amps there, enough to run everything in my car and then some. I would also be updating the charging wire from my current 10ga to likely a 6ga with the corresponding fuse link.

So, I'd love to hear your thoughts...even the guys at MAD are recommending this type of alternator. If you're using one on a small block I'd love to see some pictures as well!


'70 Duster 470hp 340/T56 Magnum/8 3/4 3.23 Sure-Grip
Re: Anyone using a GM 10si or 12si alternator on a SB? [Re: goldduster318] #205517
01/26/09 10:45 PM
01/26/09 10:45 PM
Joined: Jan 2003
Posts: 30,945
Oregon
A
AndyF Offline
I Win
AndyF  Offline
I Win
A

Joined: Jan 2003
Posts: 30,945
Oregon
I don't think they fit a SB very well which is why I designed the Denso 60 amp alternator kit. The Denso alternator fits and works.

Re: Anyone using a GM 10si or 12si alternator on a SB? [Re: goldduster318] #205518
01/26/09 10:49 PM
01/26/09 10:49 PM
Joined: Feb 2004
Posts: 4,501
Gainesville,FL
G
goldmember Offline
master
goldmember  Offline
master
G

Joined: Feb 2004
Posts: 4,501
Gainesville,FL
I went with a 12si 5 years ago and would never go back to the factory setup. The case can be easily reclocked to locate the output stud and air intake in a suitable location. Mine is spaced somewhat to match the crank trigger mounted under the crank pulley.I might have a pic from a year or so ago? I checked and have no useful pics of the setup. Andys right,it may not be as easy as it looks. In my case I wasn't using factory cylinder heads which may have made it even easier. They are cheap and if you can make it fit I doubt you'd find a better a setup.

Last edited by goldmember; 01/26/09 11:08 PM.
Re: Anyone using a GM 10si or 12si alternator on a SB? [Re: goldmember] #205519
01/27/09 12:15 AM
01/27/09 12:15 AM

A
Anonymous
Unregistered
Anonymous
Unregistered
A



I used to run these a LONG time ago, back around 74 when I had the 340 in my '70 RR body, and later, when I had a SB in my old Landcruiser

They are very easy to adapt. So easy, that I don't remember the details, seems to me I just make a new spacer and played with the front spacing as well, I may have heated and bent the tension link, I don't remember.

In my opinion, you guys put way way WWAAAYYYY too much into this notion of "no charge at idle." Just how much do you idle at 800 RPM? Hell there were THOUSANDS (millions) of these old alternators that managed (somehow) to work just fine back then.

When my '70 (440sixpack) was in "its prime" I at some times had a considerable amount of amateur radio gear in the trunk, and part of it was VACUUM TUBE gear (ex-police, taxi, etc)

I ran 4537 landing lights in that car for a long time with no issues-- 100w per lamp

When you hook up the older GM, do NOT depend on this "self excitation" nonsense, which they were never designed to do. I've forgotten, but you can tie one reg. term to the battery term, but it SHOULD have a separate "sense" lead for more accurate regulation, and the other should go through an isolation diode (replaces the idiot circuit) to a keyed (ign on) spot.

Like this:

http://www.softcom.net/users/acnss/image/DelcoSI2wiring.jpg

only we didn't use a resistor, just a diode in the no1 lead, and once again, more accurate to run no2 directly--separate wire--clear to the battery

This diagram

http://www.autozone.com/images/cds/gif/large/0900823d8015a3ab.gif

shows a 10 ohm resistor in the excitation lead

LAST I modified at least one of them to bring out the brushes --may have been the early frame external reg.---and hooked it up to a '70--later Mopar regulator

Re: Anyone using a GM 10si or 12si alternator on a SB? #205520
01/27/09 02:46 AM
01/27/09 02:46 AM
Joined: Feb 2004
Posts: 4,501
Gainesville,FL
G
goldmember Offline
master
goldmember  Offline
master
G

Joined: Feb 2004
Posts: 4,501
Gainesville,FL
Not everyone needs to upgrade and most "racers" like the "1 wire" alt,but not me. I race my car on the weekends and use the electric fan between rounds and frequenty have to restart the car multiple times while in the staging lanes and run the fuel pump,ECU,ignition,fan,etc. A strong charging system really is a money maker.I don't haul a battery charger to the track as my car has a good one built in. Yes run the sense wire to a junction block or battery not the batt stud on the alt.

Re: Anyone using a GM 10si or 12si alternator on a SB? [Re: goldmember] #205521
01/27/09 10:54 AM
01/27/09 10:54 AM
Joined: Jan 2003
Posts: 1,482
Lake Orion, MI
goldduster318 Offline OP
pro stock
goldduster318  Offline OP
pro stock

Joined: Jan 2003
Posts: 1,482
Lake Orion, MI
I did end up finding these pictures by searching Google for this topic...not the cleanest install, but it gives you an idea about the size. It doesn't look like the pulleys are lined up well but it looks like if someone could push the bearing bump-out beyond the edge of the cylinder head, you'd be golden.



I would be using the factory GM style "3 wire" setup for the best performance.

I'd say people only lived with the old lights dimming at idle and no charge at idle because they had to. All the more modern cars i've ever owned can maintain a solid 14.2-14.8v at idle with all the accessories on. The duster can't even maintain 13v with nothing on at low idle. As soon as the headlights are on, you're down to 11.5 or so volts...that's with no wipers, radio or anything else on. That is a problem in my book. You're getting discharge when you're in traffic, which is cutting spark energy and possibly shortening the life of your battery, radio, ignition boxes, etc.

I also have my worries about using the small denso one...sure it makes 60 amps at cruise, but what does that make at idle? I'm still not even sure if that would fit with the magnum heads that have larger ends on the heads (kind of like the edelbrocks).

I may end up adding an electric fan and an electric fuel pump to this car down the road as well, and i'd likely be right back to where I started if I don't have an alternator that can supply at least 45amps at idle.


'70 Duster 470hp 340/T56 Magnum/8 3/4 3.23 Sure-Grip
Re: Anyone using a GM 10si or 12si alternator on a SB? [Re: goldduster318] #205522
01/27/09 11:06 AM
01/27/09 11:06 AM
Joined: Jan 2003
Posts: 30,945
Oregon
A
AndyF Offline
I Win
AndyF  Offline
I Win
A

Joined: Jan 2003
Posts: 30,945
Oregon
The Denso alternator provides plenty of amps at idle and it fits the Edelbrock heads just fine. I did my research on the subject before I designed that kit.

Re: Anyone using a GM 10si or 12si alternator on a SB? [Re: AndyF] #205523
01/27/09 02:19 PM
01/27/09 02:19 PM
Joined: Jan 2003
Posts: 1,482
Lake Orion, MI
goldduster318 Offline OP
pro stock
goldduster318  Offline OP
pro stock

Joined: Jan 2003
Posts: 1,482
Lake Orion, MI
I'd certainly like to be able to at least have the capacity to run everything that is installed on my car at full blast at idle at the same time, like you can on a modern car. The only thing that seems to upset my colorado is when the ABS comes on and the engine is down at idle since the clutch is in.

I also cross-referenced the alternator that is on the car right now that i picked up from an 83 slant six truck. Turns out its a 65amp squareback unit, Duralast DL75334.

If I use the tech archives for a listing of common current draws for items in the vehicle, I would have currently:

Component
AMPS

Backup Lights 4.20
Headlights 8.40
Heater -Defroster 10.00
Instruments 1.00
Instrument Lights .96
Ignition 2.00
License Plate Light 1.18
Parking Lights 1.26
Stop Lights 4.20
Tail Lights 1.81
Turn Signal 4.20
Windshield Wiper - Electric 4.00

for a total of 43.21 amps, and probably take 4.2 amps off for the backup lights, so 39.01 amps

I also have a 140 watt stereo, so say we were at 14.4v, that's an additional 9.7 amps. That would easily bring my total to 48.71 amps. That being said, I know the stereo doesn't always draw this much but I like to rock out just like everyone else. There may also be even more current dissipated by the older wiring that exists to some of these items.

I'd love to see an actual curve on the small Toyota denso if anyone has one for comparison. They do typically come with GOOD aftermarket reman alternators.

I do know that if I got the 12si 94amp to fit, i'd still have plenty of headroom for future add-ons...even at idle. I'm also very likely to drive this car a lot, even at night, and use everything including the wiper motor, radio, head lights, etc all at the same time.

If my 89 Denso didn't have the output stud where its located, that would have likely worked ok.

Just trying to get some discussion going.


'70 Duster 470hp 340/T56 Magnum/8 3/4 3.23 Sure-Grip
Re: Anyone using a GM 10si or 12si alternator on a SB? [Re: goldduster318] #205524
01/27/09 03:53 PM
01/27/09 03:53 PM
Joined: Oct 2008
Posts: 765
Shoreline, Washington
72roadrunnergtx Offline
super stock
72roadrunnergtx  Offline
super stock

Joined: Oct 2008
Posts: 765
Shoreline, Washington
Have you considered just upgrading your existing squareback with a kit such as this ?
105 amps for $43.


1972 Road Runner GTX 440 6bbl 5-speed
[img]http://72rrgtx.com/carpics/bucket/DSC06730r-1.jpg[/img]
Re: Anyone using a GM 10si or 12si alternator on a SB? [Re: 72roadrunnergtx] #205525
01/27/09 04:16 PM
01/27/09 04:16 PM
Joined: Jan 2005
Posts: 12,406
Kalispell Mt.
H
HotRodDave Offline
I Live Here
HotRodDave  Offline
I Live Here
H

Joined: Jan 2005
Posts: 12,406
Kalispell Mt.
I think people over complicate it, make sure you have good wires and conectors and a decent altenator won't discharge at idle.

My 68 cuda always dimmed the lights for the last 2 years at idle till the original altenator died a couple months ago. I installed an altenator for a 75 chrysler from oreilley auto parts and at the same time put on a VR from NAPA that was listed for my car, I soldered new conectors on instead of the factory clamp on junk now it no longer discharges at idle with the engine fan full speed, heater fan on high, brake lights and head lights on and electronic ignition running at 800 rpm idle. There is a second field wire on the newer altenator just find a good ground and make a good wire to go to it.

If I needed more I would upgrade to the denso altenator, way more reliable and puts out lots of amps at very low RPM


I am not causing global warming, I am just trying to hold off a impending Ice Age!



Re: Anyone using a GM 10si or 12si alternator on a SB? [Re: HotRodDave] #205526
01/27/09 04:43 PM
01/27/09 04:43 PM
Joined: Jan 2003
Posts: 1,482
Lake Orion, MI
goldduster318 Offline OP
pro stock
goldduster318  Offline OP
pro stock

Joined: Jan 2003
Posts: 1,482
Lake Orion, MI
Those upgrade kits are inexpensive, yet I still have yet to see anything about the idle amperage. I have heard that some of them are actually worse than the stock alternator. Not to mention I have longevity concerns with souped up alternators in cases not designed with them.

As for the '75 model year chrysler alternator..are you using a squareback or one of these big ugly's (which are great alternators, just large and heavy)


The GM 10/12si and the CS series alternators appeal to me as they clean up how much is on my firewall as well as being extremely easy to come by. They also put out a lot of amperage at idle.


'70 Duster 470hp 340/T56 Magnum/8 3/4 3.23 Sure-Grip






Powered by UBB.threads™ PHP Forum Software 7.7.1