Alternator Upgrade...Single Wire?

[Bonebag]

Hi all. Getting ready to do an alternator upgrade on the 318. With the Sniper FI and all the other gadgets it's not happy and the Sniper dash let's me know that the voltage supply is not adequate from time to time, along with dim lights. Starting battery is an optima red top and cables are in good condition.  I'm wondering whether a simple alternator rebuild with a push up to 80amps or so will do the trick or if I should put in a one wire alternator and bypass the dash all together? Anyone do this and what are the in's and outs? Thanks much.

[Bonebag]

Ok..well I did this mod and so far so good. I'm on about 60 miles with the new 160 amp dodge alternator from power master. (this is a single wire that fits the dodge mount but it is a chevy case alternator). Be aware of people trying to scare you away from single wire systems, they are much better than they were a handful of years ago. You will not be able to put this on your stock 70s dodge without starting your engine bay and dashboard on fire unless you re-wire. On my 72, the wire size running from the alternator to the voltage regulator and to the dash, then to the battery (about 30') was 10G!!! The stock alternator mount will not work and this mod requires some fabrication skills...minor skills but here you go. I cut the spacers that came with the alternator to fit the top bracket on the 318. The alternator had a concentric aluminum shaft that was tapped off center to help put tension on the belt. I bought a 5/8 .625 aluminum rod from my local metal superstore for like 10 bucks (warning..do not order from amazon, they say they are 5/8 but they are mm sized and you will need a lathe to get these to work), cut it to size, sanded it a bit, drilled and tapped one side to 3/8 and the other to 1/4-20. I used a 3/8 bolt to tighten a Heim Joint to one end. I removed the alternator mount (Drain Coolant first, One of these bolts goes into the head and the water jacket). I drilled and tapped a 3/8 hole in the mount to attach the heim joint. I mounted the alternator and heim joint, adjusted the belt (takes 2 seconds now and zero effort to get tight). Might spend some time to get the alternator aligned perfectly with the other pulleys in the near future but I have zero squeals and it's pushing 14.4 volts at idle and super bright headlights. This mod did require re-wiring the starter and charging circuits, bypassing the amp meter in the dash. Not a small job and not cheap. I used 2G Welding cable from the alternator to the battery. 2G from the Battery to the Starter terminal Block, 2G to the starter and 4G to the dash for power (through a 100amp breaker) to all the accessories and Sniper FI/Engine circuits. I also rewired the entire chassis wiring system to new fuse blocks and separate relays. It's too soon to see if I burn through belts. More than one person suggested this wasn't possible and my 318 wasn't strong enough to turn a 160 amp alternator without converting to a serpentine belt system and at the minimum two belts. If I  need to run two belts I will. I'll need to most likely put a 3 belt crank pulley on and run two belts directly to the alternator.

[DaveVA78Chieftain]

You made a lot of changes. Wire rerouting and increased wire gauge size by themselves would have seen a improvement by themselves.  Add in the replacement of old weathered wire connections and you get even more of an improvement.  Hard to say at this point how much of an improvement those changes alone would have made.  Remember though, original system was actually only designed to just support the chassis system.

1. With just the normal engine loads how many amps does the rig draw right after starting then taper off to after say 20 minutes of driving (MOM/DUAL/NORM set to NORM)?

2. Using the same conditions as 1 how many amps are drawn with the headlights ON. Oh, I assume stock headlights are still installed.

3. With both chassis and coach batteries at full charge how many amps are drawn when with the MOM/DUAL/NORM set to DUAL (headlights OFF, Fridge not set to 12VDC mode, Furnace OFF, and any added inverters are OFF)?

4. Using the same conditions as 3 how many amps are drawn with the headlights ON, Fridge not set to 12VDC mode, Furnace OFF, and any added inverters are OFF.

5. Using the same conditions as 3 how many amps are drawn with the headlights ON, Fridge set to 12VDC mode, Furnace OFF, and any added inverters are OFF.

6. Using the same conditions as 3 how many amps are drawn with the headlights ON, Fridge set to 12VDC mode, Furnace ON, and any added inverters are ON.

Now shut the engine and Headlights OFF, set MOM/DUAL/NORM set to NORM, but leave the Fridge set to 12VDC mode, Furnace ON, and any added inverters are ON.

Let rig set for say 3-4 hours to get a good draw down on the coach battery (eg: boondocking at the lake).

Now, with Fridge set to 12VDC mode, Furnace ON, and any added inverters ON,  start the engine, turn Headlights ON, and set the MOM/DUAL/NORM set to DUAL.

Now that the new alternator is actually being asked to do close to what it was designed to do, what's the amp draw, is the engine straining at idle, how is the single belt holding up to the strain it is not designed to do?

Oh, almost forgot, when the belt breaks due to overload in this condition, you are 50 miles out of town, and the engine overheats because the belt broke what-cha-gonna-do?

This is the point that others are saying it is not designed to handle.
Though 160amp was a bit of overkill (100amp is more than enough), not saying this is not a good upgrade but needs some beefing up on the drive side. In fact anything above stock needs 2 belts or serpent.  Also anyone attempting this on these older motorhomes need to heed Bonebag's comments about the needed wiring upgrades.  The 72 and earlier stock routing of the main ALT wire through dash AMP gauge is a know Dodge design weak spot.

[Bonebag]

that's gonna take me some homework Dave

I have a couple spare belts and I'm in the testing phase now. The Sniper dashboard will tell me immediately when I lose the belt and the charge drops below 13v. I have a relay to connect both batteries but am using a Victron DC/DC charger to charge the house battery. I'll get you some answers soon and thanks much BTW, I've used your knowledge base and experience much throughout this journey..and it's very much appreciated.

[DaveVA78Chieftain]

Ahh, even more to this story comes to light!
To better understand where I am coming from, a lot of people come here to learn how to maintain, repair and upgrade their rig. You are making many upgrades that may be well beyond many peoples understanding without full details being provided. So, I am speaking up to ensure people understand all this before possibly trying to duplicate your setup without having all the information available.  The rewiring job you did is complex by itself.  Are you aware that the alternator wiring of a pre 74 M300/M375 rig is different from 74 and later M300(RM300)/M400(RM350)/M500(RM400)/M600 rig.  Also the 69 F19 (ford P350 chassis) is all together different.  That alone could create problems for the unaware.  So, I am cautioning people to be fully aware of what their doing before attempting something like this.

Based on the limited information you provided in your original explanation I was trying to demonstrate that you were not using anywhere near the 160 amp capability of the alternator, most likely less than 25% (40 amps) if even that much.  If you have some sort of an issue (say you forgot and left the headlights ON during the day while the engine was OFF) and the coach battery  was also being used then, the batteries may get very low such that you barely get the engine started. Once started that oversized alternator is going to be pumping out a whole lot of current trying to restore the charge of two nearly depleted batteries.  That's is when the other issues will raise their ugly head and place to much of load on the small engine and a single belt.  While the Victron DC/DC charger may limit it's max draw to around 33 amps (depending on model and coach battery state) combined with a low chassis battery condition may overload your setup. The Victron DC/DC charger is a 3 stage charger meaning it puts out near maximum amp output initially if the battery is low and tapers down to a trickle charge when battery is close to fully charged.

[Bonebag]

Oh yeah..I probably should have just started one big post with all the mods. I'm running a Holley Sniper with external fuel pump that draws more amperage than the stock setup altogether. I switched all the lights to LED except the headlights. The headlights are now "modern" H4 set up and are being fed by 10g wires including the grounds of course. I also have a stereo system with amp that draws about 25 amps. Together with the sniper that's almost 40 amps without lights, fans, heat, air compressor for the shocks, wipers or any of the house acc that are on while moving. Yes the 160 amp is overkill but I researched the hell out of products and found this unit to be the best bet, plus the tech people called me back directly anytime I had a question. I'm curious to see what happens when the batteries are low...sounds like a weekend experiment. I had read a few posts recently with people commenting that the heim joint adjuster had stopped most issues with single belt feeds. I'm pretty down and close with electricity but this task was complex and I wouldn't advise it to most diy mechanics. I've been testing and checking continuity during this task, thinking and rechecking after any significant change. Wonder if there is a way to manually throttle the voltage regulator? Thanks again Dave!

[Bonebag]

Oh yeah..I probably should have just started one big post with all the mods. I'm running a Holley Sniper with external fuel pump that draws more amperage than the stock setup altogether. I switched all the lights to LED except the headlights. The headlights are now "modern" H4 set up and are being fed by 10g wires including the grounds of course. I also have a stereo system with amp that draws about 25 amps. Together with the sniper that's almost 40 amps without lights, fans, heat, air compressor for the shocks, wipers or any of the house acc that are on while moving. Yes the 160 amp is overkill but I researched the hell out of products and found this unit to be the best bet, plus the tech people called me back directly anytime I had a question. I'm curious to see what happens when the batteries are low...sounds like a weekend experiment. I had read a few posts recently with people commenting that the heim joint adjuster had stopped most issues with single belt feeds. I'm pretty down and close with electricity but this task was complex and I wouldn't advise it to most diy mechanics. I've been testing and checking continuity during this task, thinking and rechecking after any significant change. Wonder if there is a way to manually throttle the voltage regulator? Thanks again Dave!