Replacement Alternator AMP Max

[Tyron68]

Needing to replace my alternator (68 charger 440, added AC). The alternator that was on the car had part # 3874271 on back. What is the biggest amp alternator I can go with without upgrading wiring?

 

[ckessel]

Maybe the 78 amp unit that came on the K cars. Back in the late 80's/early 90"s, that was an upgrade suggested on Mopar Action. I put that on my 70 Challenger. Pulley was different though but thats an easy swap. Going more than that, it would be a good idea to upgrade the wiring.

 

[RJRENTON]

Needing to replace my alternator (68 charger 440, added AC). The alternator that was on the car had part # 3874271 on back. What is the biggest amp alternator I can go with without upgrading wiring?

Use the 46 amp alternator that came as standard equipment on A/C vehicles. Changing the drive sheave, requires a special pulling tool and the alternator must be disassembled to press on the drive sheave (using a press to put it on in the position for belt alignment) as it's an interference fit. DO NOT heat the sheave to put it back on. Refer to the FSM for proper method......just my opinion.....
BOB RENTON

 

[Nacho-RT74]

Maybe the 78 amp unit that came on the K cars. Back in the late 80's/early 90"s, that was an upgrade suggested on Mopar Action. I put that on my 70 Challenger. Pulley was different though but thats an easy swap. Going more than that, it would be a good idea to upgrade the wiring.

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This could be a good option on the cheap, which with the propper pulley size (the one used on 80s alts) will be able to source up to 45 amps at iddle. Very important load capacity to feed the A/C blower along with some other accessories. Still a bit short if raining and needing to turn on wipers with A/C on (depending on blower speed selected thought) at a traffic light on nights.

However, like mentioned I still would advice get AT LEAST one straight path between alt stud and ammeter withouth going throught the bulkhead. If you are keeping the factory one throught the bulkhead, add a 12 gauge extra path won’t hurt. Not a huge or hard to make upgrade, just add one wire. But still check the factory charging circuit conditions at bulkhead.

My Charger was a daily driver for long time into the tropic so A/C was a bit of mandatory and this alt made a huge difference on the car with accs response.

These alts are around couple of millimeters wider and fits a bit tighter. On my 74 400 at least I had to get a longer belts setup because the rear of the alt was meeting with the block, so a longer belt will sway the block. Also had to grind a bit the rear spacer for a better belt alignment ( more reason to get a longer belt setup).

For a 68 if still using single field alt, using this alt will need to ground one of the alt brushes.

 

[Tyron68]

Use the 46 amp alternator that came as standard equipment on A/C vehicles. Changing the drive sheave, requires a special pulling tool and the alternator must be disassembled to press on the drive sheave (using a press to put it on in the position for belt alignment) as it's an interference fit. DO NOT heat the sheave to put it back on. Refer to the FSM for proper method......just my opinion.....
BOB RENTON

Bob, why is replacing the drive sheave required?

 

[Tyron68]

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This could be a good option on the cheap, which with the propper pulley size (the one used on 80s alts) will be able to source up to 45 amps at iddle. Very important load capacity to feed the A/C blower along with some other accessories. Still a bit short if raining and needing to turn on wipers with A/C on (depending on blower speed selected thought) at a traffic light on nights.

However, like mentioned I still would advice get AT LEAST one straight path between alt stud and ammeter withouth going throught the bulkhead. If you are keeping the factory one throught the bulkhead, add a 12 gauge extra path won’t hurt. Not a huge or hard to make upgrade, just add one wire. But still check the factory charging circuit conditions at bulkhead.

My Charger was a daily driver for long time into the tropic so A/C was a bit of mandatory and this alt made a huge difference on the car with accs response.

These alts are around couple of millimeters wider and fits a bit tighter. On my 74 400 at least I had to get a longer belts setup because the rear of the alt was meeting with the block, so a longer belt will sway the block. Also had to grind a bit the rear spacer for a better belt alignment ( more reason to get a longer belt setup).

For a 68 if still using single field alt, using this alt will need to ground one of the alt brushes.

I am planning on doing the ammeter bypass at some point as that seems to be something a number of people on this forum are recommending. I did buy and install the headlight relay kit from crackback.

 

[Nacho-RT74]

No need to bypass the amm, just source correctly all the accesories… and I would check the ammeter itself, not just outside but inside disassembling it.

My Charger is (was untill I dissasembled for a deeper resto job) a REAL daily drive car with A/C with stock system including ammeter… with that 78 amps alt and everything sourced correctly. Including halogen headlights with relays system, trust me. The amm needle barely flicked.

Also installed relays for each one of the blower speeds.

Those amm bypass recomendations comes mostly from ppl who don’t understand or don’t want to understand how to make it to work propperly. Or are still affraid about it.

 

[RJRENTON]

Bob, why is replacing the drive sheave required?

Because if, you are going to use the 46 amp alternator from an A/C vehicle, a double belt arrangement was used. You did not state if you're using the Chrysler RV2 Ccompressor or rhe Sundun.....which may or may not use a double belt drive. I assumed the double groove sheave. In all regards, special tools and techniques are required remove/installed the sheaves on a Mopar alternator. Accurate information results in accurate suggestions to your query........
BOB RENTON

 

[Tyron68]

Because if, you are going to use the 46 amp alternator from an A/C vehicle, a double belt arrangement was used. You did not state if you're using the Chrysler RV2 Ccompressor or rhe Sundun.....which may or may not use a double belt drive. I assumed the double groove sheave. In all regards, special tools and techniques are required remove/installed the sheaves on a Mopar alternator. Accurate information results in accurate suggestions to your query........
BOB RENTON

Understand. My set-up is a single belt with vintage air kit.