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460 swap into a 78 Bronco

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Gary Lewis

Re: 460 swap into a 78 Bronco

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ArdWrknTrk wrote

What loads do you intend to put on the existing cab harness, that would exceed 70A?

That's the key. If the battery-charging load is taken off the shunt by moving the alternator's output to the starter relay then the shunt is only carrying whatever load is in the cab. And if you put a headlight relay harness in that part of the load goes away. Ditto the HVAC fan.

But if the battery is still being charged through the shunt it is likely you'll have problems at some point. For instance, if you let the battery get really low and have to jump-start the engine the alternator is going to kick out everything it can to bring that dead battery up to 14.4V. If you have a 100A 1G in and kick the fast idle off quickly then you may get by as that alternator won't give you more than 70A until you get above idle. But Jim's 3G alternator tested at 106A at 1600 alternator RPM, which is about 550 engine RPM assuming you use the standard 460 pulley.

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

viven44

Re: 460 swap into a 78 Bronco

In reply to this post by ArdWrknTrk

The worst case scenario would be all of the below running

- Headlights/Stop light/Turn signals
- Electric choke
- Electric low-pressure fuel pump
- AC/Blower
- Maybe a decent speaker/radio
- Electric fan - TBD, only if the clutch fan isn't doing its job

Vivek

- 'Big Blue 2WD' - 1984 F350 RWD 460/C6
- 1978 Bronco with the heart of a 1986 F250 Bullnose - under restoration
- "Bonded Bronco" -1985 Bronco - 302 4-speed fuel injected, Hibernating future project

viven44

Re: 460 swap into a 78 Bronco

This post was updated on .

In reply to this post by Gary Lewis

I don't believe the shunt is truly bypassed in that case is it ? It will still carry about half the load (2 resistances in parallel). The shunt will always shunt

Also I wound't want to bypass the fusible link as it is the safety net if the alternator malfunctioned or shorted internally. Don't ask me how I know

viven44

Re: 460 swap into a 78 Bronco

In reply to this post by Gary Lewis

Gary Lewis wrote

And if you put a headlight relay harness in that part of the load goes away. Ditto the HVAC fan.

I thought about relay usage and its effect on alternator load. Even if the current was directly taken off the battery, wouldn't the alternator be in the "loop" and make up for that current loss. This is waay over my ability to predict, Gary, you are definitely better in electrical assessment. I try but always overlook something

Gary Lewis

Re: 460 swap into a 78 Bronco

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In reply to this post by viven44

Wire it this way but don't add the relay nor cut the Y/LG wire on Ckt 654 unless you are installing a Rocketman voltmeter. The output of the alternator goes directly to the battery and not through the shunt. Only the load "in the cab", meaning that going through fuse link L or M which go to the ignition switch, will go through the shunt. Which means the ammeter will always show discharge.

And, you should not put a cooling fan on "cab power". The wiring wasn't sized for that much load. Instead put relays out by the fan, powered directly from the battery/starter relay and use key-on power to pull them in.

But, having said all that, we've had a long discussion about a better way to wire these trucks and I shipped Jeff/Big Bro 84 a harness to prove out that plan. If you want to read how that is to be done go to this thread, but let's not rehash it here.

Gary, AKA "Gary fellow": Profile

Gary Lewis

Re: 460 swap into a 78 Bronco

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In reply to this post by viven44

Assuming you power the relays directly from the battery or the starter relay, which is easier, then using relays to power high-current devices takes the load off of fuse links L & M, meaning off the cab. Yes, the alternator is still in the loop, but the only load on L or M is the miniscule pull-in current.

Gary, AKA "Gary fellow": Profile

viven44

Re: 460 swap into a 78 Bronco

In reply to this post by Gary Lewis

OK thanks!! Yes, even for the fuel pump I will be using a relay. Horn, Fuel pump always on relay. I figured the fan was a significant current draw so a relay would be needed. The reason I didn't mention relays above is that I was pretty sure even if relays were used the alternator and shunt would see the load. But adding a second charging cable will help definitely. Its almost like halving the resistance of the shunt itself.

I'll read that thread fully.

Gary Lewis

Re: 460 swap into a 78 Bronco

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You do not want the shunt to see the load if you are adding things like electric cooling fans. And there's no reasonable place for you to get power for the relays after the shunt. So just tie into the starter relay's battery connection and run a fused wire to a fuse/relay unit like Jim and others have. Each individual relay can then have its own fuse and you have everything in a neat unit.

But I don't understand what you mean by "But adding a second charging cable will help definitely. Its almost like halving the resistance of the shunt itself." You don't want to add a second charging cable. The big red X means to take the factory charging cable out and replace it with one directly to the starter relay.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: 460 swap into a 78 Bronco

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In reply to this post by viven44

The fan & choke are NEVER going through the shunt.

The clutch driven fan will always be sufficient (if you have a proper shroud)

Gary already mentioned it, so I'm not going to point out the stupidity of electric fans in a remotely stock configuration..

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: 460 swap into a 78 Bronco

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Delco Remy says an alternator is 55% efficient. ScienceDirect says an electric motor is between 70 & 96% efficient. So if we assume the motor is 80% efficient then converting mechanical energy to electric energy & then back to mechanical will be .55 x .80 = 44% efficient. And that, in a nutshell, is Jim's point.

Gary, AKA "Gary fellow": Profile

viven44

Re: 460 swap into a 78 Bronco

In reply to this post by viven44

In my case, I'm not adding a separate voltmeter, the stock gauge will do the job (even if it doesn't really). I test my charge voltage very periodically for ripples, swings upon load on/off, battery health.... :) :)

I don't plan to remove the shunt as my expected loads are <70A.

And sorry for the brain fart, I understood that X meant removal of the primary charge cable, but for some reason momentarily forgot about that. Makes sense why it is redundant if you are replacing the voltmeter, and adding the new charge cable.

ArdWrknTrk

Re: 460 swap into a 78 Bronco

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I'm going to suggest that you fuse that shunt at 75A.
Because if you have a short in the cab it's going to vaporize like an exposed incandescent filament....

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

viven44

Re: 460 swap into a 78 Bronco

In reply to this post by ArdWrknTrk

I have never installed an electric fan, but again all the hipsters I talk to in my generation swear by it. As you know, I will upgrade the radiator, even the fan clutch before resorting to alternate means

And Jim, Gary mentioned it here maybe a few exchanges ago, but I will no longer bring up the topic of energy conversion intentionally here and raise your blood pressure...

That I STUPID, I get that. Just like the short-term plan "in the world" where fossil fuels are used to make bulk of the electricity to drive electric vehicles. Maybe I'm the dumb one who doesn't understand why that makes sense even short term.

Gary Lewis

Re: 460 swap into a 78 Bronco

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In reply to this post by viven44

You don't need to install a voltmeter or remove the ammeter. But if you move the alternator's output to the starter relay, which is HIGHLY recommended if you go with an alternator with more than 70A output, then your ammeter will only show a discharge, and that will grow as you bring on more loads. If you understand that then all is ok.

Gary, AKA "Gary fellow": Profile

viven44

Re: 460 swap into a 78 Bronco

In reply to this post by ArdWrknTrk

I have installed a Maxi-fuse in place of a fusible link before and it worked well. But that was in a truck where the previous ding-dong blew up the fusible link and just had a staight-up 12 gauge wire.

In this case, it will be Stock alternator, stock everything. Maybe better speakers, and radio, the stock fusible link should do it. It is still very much intact and healthy!

ArdWrknTrk

Re: 460 swap into a 78 Bronco

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In reply to this post by viven44

You might be surprised how much electricity is powered by renewables.
Almost all of Canada is hydro.
China installed more solar last year than the US has in total.
Australia has an almost perfect climate for solar.
Much of northern Europe is offshore wind (GB, Denmark, Netherlands & the Scandi countries)
Iceland is 100% geothermal...

Coal & gas power make sense because fixed plants have had over a century to optimize, like well over 60% compared to maybe 30% for ICE.

So, even with transmission losses and conversion in an electric motor you are still miles ahead of petroleum.
And a ICE will ALWAYS burn fuel.
An electric is agnostic.
Nuclear, solar, wind, hydro, gas or coal... it doesn't care where the electrons come from.
So the changing face of the grid only makes improvements in efficiency.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

ArdWrknTrk

Re: 460 swap into a 78 Bronco

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In reply to this post by viven44

How many amps can your battery deliver?

Because that's what counts. 🔥💡

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

viven44

Re: 460 swap into a 78 Bronco

I agree, that's a good point... in a wire short situation, assuming what is shorted is not protected by a fuse, it will be a smoky spectacle. And it better be a smoky one because you don't want the leakage to persist under the radar. Fuse is definitely the best thing to do. I personally am comfortable with a fusible link because I am very particular about monitoring current draw on all my classics. I take the wiring part very seriously as well. On the Bronco, I pulled out all the wiring "enhancements" from the previous owner. It is completely stock.

For example, on the Bullnoses, I have used the clamp meter quite a bit to study all of them. On cold start the current flow into the battery is approx ~15A and if the battery is really low in charge, closer to 25A. When everything is in steady state and all lights / AC are off and the battery is charged, a mere 3-4A is all that's flowing through the "loop". When AC and headlights are on, the total draw is as high as 35-40A.

On my Bronco now, I have the clamp meter permanently attached to battery negative until i'm comfortable with it and a good baseline is established. If it doesn't meet my baseline expectations I'll go into every wire/fuse and see where the higher current draw is.

ArdWrknTrk

Re: 460 swap into a 78 Bronco

Administrator

Alternator in & out of the battery is one thing. (But again, 1G & 2G alternators don't really put out much at lower rpm)
I'm talking about the battery dumping into the cab harness (protected by 2 fuselinks at the splice)
Ammeters aren't telling me the actual state of charge, like a voltmeter does.
And, I really don't care if I'm having a charge or discharge situation, except long term..
Like there's too much load for an alternator to keep up.
With the 130A 3G (that can put out 160) I never have to worry.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

viven44

Re: 460 swap into a 78 Bronco

So how about adding a maxi fuse between the starter solenoid and fusible links ? Maybe thats what you've been saying all along. I had incorrectly assumed you wanted me to get rid of the fusible links (sorry).

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