alternator

**money pit** · 10-27-11, 10:54 AM

85 vette how do i find out if i have 120 amp or 108 amp. alternater need to be replace keep geting asked same ?

**gmjunkie** · 10-27-11, 02:25 PM

Originally Posted by money pit

85 vette how do i find out if i have 120 amp or 108 amp. alternater need to be replace keep geting asked same ?

You may have to remove it to see it,But it should be stamped on the alternator case!~!!

**boomdriver** · 10-27-11, 09:23 PM

Question to Junkie or anyone that would know....

would it harm the system to install a 120 where a 108 used to live? There is enough demand that the extra amperage would be used I'd think.

Were there both 108 and 120 amp alts used on C4s ?

**gmjunkie** · 10-28-11, 03:54 AM

Originally Posted by boomdriver

Question to Junkie or anyone that would know....

would it harm the system to install a 120 where a 108 used to live? There is enough demand that the extra amperage would be used I'd think.

Were there both 108 and 120 amp alts used on C4s ?

No not really if it mounts the same,the system is only going to charge what it needs.I put 200 amp Alt for a Chevy Cop Car on my Olga Truck after I added a second winch and battery set up! I didn't have to change the wiring a bit except to tie the second battery and winch into the system,I did have to modify the mounting brackets a little to keep it up off my LS6 Big Block valve cover though,But I don't have to leave the truck running so it will start after I'm winching anymore and I can jump start a Caterpillar!

**boomdriver** · 10-28-11, 07:09 AM

Originally Posted by gmjunkie

No not really if it mounts the same,the system is only going to charge what it needs.I put 200 amp Alt for a Chevy Cop Car on my Olga Truck after I added a second winch and battery set up! I didn't have to change the wiring a bit except to tie the second battery and winch into the system,I did have to modify the mounting brackets a little to keep it up off my LS6 Big Block valve cover though,But I don't have to leave the truck running so it will start after I'm winching anymore and I can jump start a Caterpillar!

Cool

Thats kinda what I figered. I was wondering because the next time I was going to look for the bigger alt. My stock size does exactly what it is supposed to do but when everything is on while sitting at a stop lite it does dip below 12v....jumps back to 13+ with the slightest increase in rpm so I'm not concerned, I'd just like to see a charge at all times and not a trade at low speed.

Thanks for the info !

**TedC** · 10-28-11, 09:30 AM

Originally Posted by boomdriver

My stock size does exactly what it is supposed to do but when everything is on while sitting at a stop lite it does dip below 12v....jumps back to 13+ with the slightest increase in rpm...

If you verified that the voltage is indeed dropping to less than 12 volts , then I would suggest your charging system is not working properly. I'm guessing you have a stock setup with no belt speed reduction modifications. I have a similar rated alternator in my 1989 and with the high beams, rear defogger and primary engine fan on the voltage remains in the upper 12 volts to upper 13 volts range at idle. On my 1988, I had a similar problem as you describe and that was resolved by replacing the alternator.

**LLC5** · 10-28-11, 05:24 PM

Originally Posted by boomdriver

Cool

Thats kinda what I figered. I was wondering because the next time I was going to look for the bigger alt. My stock size does exactly what it is supposed to do but when everything is on while sitting at a stop lite it does dip below 12v....jumps back to 13+ with the slightest increase in rpm so I'm not concerned, I'd just like to see a charge at all times and not a trade at low speed.

Thanks for the info !

A higher output alternator will not necessarily change the charging voltage at idle, that is controlled by your idle speed and the internal windings of the rotor and stator. If you do go up in amperage output make sure that the battery feed wire is large enough to handle the additional current flow. Good luck with it.

**John Robinson** · 10-29-11, 02:02 AM

You don't say if you are looking at the analog or digital gauge. My gauges read the opposite of what your's are they read as high as 15.2 volts down to 14.5. Here is what I did to find out that the analog and digital gauges were way off.

gigarplug002.jpg

I bought a cigar lighter adapter from radio shack that had an on off switch and an inline fuse. Then I simply hooked my meter to it and checked the voltmeter readings against the analog and digital readings in the car.

You may find that you only have a problem with the cars gauges and not the charging system.

**Curious George** · 11-03-11, 10:38 AM

If you're going to upgrade your alternator, with say a Power Master unit, then you can usually just bolt these on and not have any issues.

However, if you have a stock (CS130 / CS144 for example) unit rebuilt (DIY or otherwise) say above 150 amp, you will more than likely need a overdrive pulley (slightly smaller diameter) to increase the rotor speed at idle to maintain correct operation. The increased windings on the high output stator require more magnetic field from the rotor, at low idle speeds. In some cases, the voltage regulator may fall out of regulation at factory idle speeds with a high output stator and OE size pulley.

My preference (from a technical point of view) was to have the rotor rewound, but no one was willing to do that, so a new pulley works just as well.

I rebuilt a CS130 for my 1897 Camaro and used a kit from ASP (Alternator & Starter Parts Wholesale - Repair Kits - High Output Alternators - DELCO CS130 220A HIGH OUTPUT KIT)

I also ordered a smaller pulley and everything works great together.

CG

**boomdriver** · 11-03-11, 12:59 PM

Originally Posted by Curious George

If you're going to upgrade your alternator, with say a Power Master unit, then you can usually just bolt these on and not have any issues.

However, if you have a stock (CS130 / CS144 for example) unit rebuilt (DIY or otherwise) say above 150 amp, you will more than likely need a overdrive pulley (slightly smaller diameter) to increase the rotor speed at idle to maintain correct operation. The increased windings on the high output stator require more magnetic field from the rotor, at low idle speeds. In some cases, the voltage regulator may fall out of regulation at factory idle speeds with a high output stator and OE size pulley.

My preference (from a technical point of view) was to have the rotor rewound, but no one was willing to do that, so a new pulley works just as well.

I rebuilt a CS130 for my 1897 Camaro and used a kit from ASP (Alternator & Starter Parts Wholesale - Repair Kits - High Output Alternators - DELCO CS130 220A HIGH OUTPUT KIT)

I also ordered a smaller pulley and everything works great together.

CG

a real classic !