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Alt belt.

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Ifitaintbroke

Alt belt.

Been reading about the 3g swap, which I have done. It seems that others have used a single v belt with no problems? I currently have an oversized pulley which works fine, but I'm concerned the alternator work put out as much at peak because of the reduced speed. When adding more loads(winch), I know I'll need more output. I've thought of trying a small engine belt(the green kind), as I believe they are higher friction, and a normal sized pulley. Thoughts?

Bradley
86 f250 supercab longbed, 4x4, 460 bored to 472 cubes, ported heads, ARP rod bolts, EFI pistons, 5.08/5.41 lift 114° lobe separation flat tappet cam, notched lifters, Smith Brothers pushrods, stock rockers, Eddy Performer intake, Holley 1850 or 3310 depending on mood, custom curved points dizzy, MSD analog 6al triggered by Pertronix module, zf5 swap, 3g alternator, custom instrument cluster, dual tanks with 38 Gal rear for 57 Gal of fuel capacity, far too much more to mention.

98 Ranger standard cab, rwd, 5-speed, 2.5L, glass pack muffler, dual plugs wired to fire at the same time, coming up on 300,000 miles before too long.

Averaging 26-27 mpg.

South Georgia.

Gary Lewis

Re: Alt belt.

Administrator

A box stock 3G alternator puts out 106A @ 1600 alternator RPM, 134A @ 2500 alternator RPM, & 160A @ 6000 alternator RPM. And Ford put a 3:1 ratio on the 460's, so maybe your pulley isn't too large?

As for the belt, I've read that a single v-belt is not supposed to be able to handle more than about 100 amps. But people seem to make it work fine all the time, so I'd give it a try. If it doesn't work then you might look for the right pulleys to do two belts, but take it from me that isn't easy to do.

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

Ifitaintbroke

Re: Alt belt.

I tried the stock pulley when I first did the swap and it squealed like crazy. The pulley I have is about twice the diameter of the stock one, so rpms are cut in half. I'll have to do the math on that based on what you just said, but that may take a few minutes as math was not my favorite subject.

Gary Lewis

Re: Alt belt.

Administrator

The 3G comes online immediately, so when starting the truck it'll try to "fill the battery back up" very quickly. That'll make the belt squeal for sure. The fix for that is one of soft-start regulators, which are technically called LRC. This search shows several of them available from 2 seconds to 10 seconds.

Gary, AKA "Gary fellow": Profile

Ifitaintbroke

Re: Alt belt.

Thanks Gary! How hard is that to change? I've tested many an alternator at work, but I've never taken one apart.

Gary Lewis

Re: Alt belt.

Administrator

It is easy. It goes into the alternator from the back and there are a few small screws holding it in. You pull those screws and pull it out. The brushes will fly but you can put them back in and hold them in place on the regulator with a toothpick.

The new one will have its brushes held with pins and you just put it in, screw it down, and pull the pins.

Gary, AKA "Gary fellow": Profile

Ifitaintbroke

Re: Alt belt.

Ok, sounds doable. I'm looking at this one on ebay: https://www.ebay.com/itm/252825717914?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=B5GwTTXlQ5-&sssrc=2349624&ssuid=DHDx0XYjS2u&var=&widget_ver=artemis&media=COPY

The interesting this is that my alternator should have come with one as it is for a v6 mustang/taurus. What I have found with these aftermarket parts is that they are made to very loose specifications. Particularly carburetors. In my parts system at work, the same carb will be listed for a 351w and a 460. Unless I am mistaken, although the carb type would likely be the same, the jet sizing(among other things) would be different for different engines, and there were probably different carburetors for different vehicle options and the same engine. Alternators seem to be the same way. The voltage regulator I currently have is probably just a generic 3g regulator, and I highly doubt if any parts store alternator would have the lrc regulator.

Gary Lewis

Re: Alt belt.

Administrator

I think that regulator will help you.

As for what regulator you may have, the note at the bottom of that advert says "F794 without LRC. F795 with LRC". And from what I remember the F795 is white.

Concerning what the LRC regulators came on, my understanding is that they were for the vehicles with little engines because the standard regulators brought the alternator in faster than the ECU could respond when a high-current load was turned on. My 460/7.5L doesn't even flinch when loads come on, but a little 2.0L does.

Gary, AKA "Gary fellow": Profile

Ifitaintbroke

Re: Alt belt.

In other words, the reason we are using the lrc is different. Its because the belt drive cannot handle the sudden load, not the engine. It'd have to be one heck of an alternator to stall a 460.

Gary Lewis

Re: Alt belt.

Administrator

Yes, on all counts. The EEC-V system on Big Blue knows when the A/C compressor comes on and is capable of bringing the idle speed up to compensate. But it doesn't have to as you can't tell when the compressor engages.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Alt belt.

Administrator

In reply to this post by Gary Lewis

The LRC regulators are also often found in Lincoln/Mercury products.

A) the 100A inrush spike of the Mk-VIII's massive electric fan.
B) the load of 8 way heated electric seats.
C) hunting idle when the AC cycles in traffic.

I'm using my stock alternator pulley on the 130A 3G without chirp or squeal on startup.
I bought an L&L bracket to eliminate my dual AIR pump bracketry but I didn't use the larger included pulley (I sent it to Gary

)

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.

Ifitaintbroke

Re: Alt belt.

I'd much rather use smaller pulley if I can. I'll try that new regulator and see what happens!

Rusty_S85

Re: Alt belt.

Check out the last few pages or so of my Sniper install thread. I have a 3G I put on mine and I talked about the LRC regulator I went with in more detail as well as the pulley ratio what I have and what is considered ideal for a street vehicle. I went into detail on this in my thread as I have a built 302 (305 cid) that has a roller cam that makes power up to 5,400 rpm and I was concerned about spinning the 3G too fast.

"Old Blue" - '56 Fairlane Town Sedan - 292-4V, Ford-O-Matic transmission, 3.22:1
'63 Belair 2dr sdn - 283-4V, Powerglide transmission, 4.56:1
'78 Cougar XR7 - 351-2V, FMX transmission, 2.75:1 9inch
"Bruno" - '82 F150 Flareside - 302-2V, C6 transmission, 2.75:1 9inch, 31x10.50-15 BFG KO2

Ifitaintbroke

Re: Alt belt.

Can you link it to me? That sounds like an interesting read, but this forum is kind a labyrinth sometimes. I get lost easy.

Gary Lewis

Re: Alt belt.

Administrator

This post might be a good place to start on Rusty's thread.

Gary, AKA "Gary fellow": Profile

Rusty_S85

Re: Alt belt.

This post was updated on .

In reply to this post by Ifitaintbroke

Ifitaintbroke wrote

Can you link it to me? That sounds like an interesting read, but this forum is kind a labyrinth sometimes. I get lost easy.

Gary beat me to it, that is the page where I start going into the math for mine. I was looking at a larger pulley to bring the pulley ratio down on mine but decided against it as I have with a 2.50" pulley a 3:1 ratio which is ideal for a street vehicle. I found out via calipers that the pulley is larger than 2.50" which will drop the ratio down some below 3:1 to 2.71:1 which is below the recommended 3:1 ratio for a street vehicle. Turn on rpm of the alternator is 1,600 rpm on mine which means with an improper pulley ratio it would never self-excite at idle if it doesn't hit 1,600 rpm alternator speed. Mine will be at 1,600 rpm alternator speed around 500 - 525 rpm engine speed, this is why I stress to people to run an alternator that has a trigger wire as I have seen vehicles run one wire alternators and never hit that speed to self-excite.

ArdWrknTrk

Re: Alt belt.

Administrator

Rusty, 3G's have no need to 'self excite'
That's the purpose of the hot in run LG/R wire in the regulator plug

At a 3:1ratio the alternator is already turning 2,100 rpm with stock 700 idle

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.

Ifitaintbroke

Re: Alt belt.

In reply to this post by Ifitaintbroke

Update: acquired a pulley for free two days after ordering one from summit.

Gary Lewis

Re: Alt belt.

Administrator

Usually works that way, but glad you found one.

Gary, AKA "Gary fellow": Profile

Rusty_S85

Re: Alt belt.

In reply to this post by ArdWrknTrk

ArdWrknTrk wrote

Rusty, 3G's have no need to 'self excite'
That's the purpose of the hot in run LG/R wire in the regulator plug

At a 3:1ratio the alternator is already turning 2,100 rpm with stock 700 idle

Correct, but many companies are now offering the 3G in a one wire configuration in the aftermarket just like the old GM alternators that had an excite wire and was modified into a one wire alternator.

On the ratio, that depends on mine with a 3:1 ratio I was looking at 1,920 alternator rpm @ 600 engine rpm. My actual ratio after using a caliper to measure the OD of the pulley came out closer to 2 5/8" not 2 1/2" which put me at 2.71:1 ratio and gives me a 1,600 rpm alternator speed at OE 525 rpm engine speed. 2,100 rpm alternator speed with 2.71:1 ratio like I have would be at 700 rpm engine speed how ever.

At the end of the day you dont want to turn these alternators too slow otherwise they wont charge properly but you also dont want to turn them too fast as you can over spin them in upper rpm range of your engine. They are also various statements out there of what rpm alternator speed that the 3G can handle but nothing clear cut. Last I saw was 18,000 was what most can handle but Ive seen that number as low as 15,000 rpm, I hopefully am ok with my setup at 2.71:1 ratio as im looking at 16,762 rpm @ 5500 rpm engine speed which would be my shift point and redline of 6,000 rpm engine speed would spin the alternator at 18,286. With the 3.07:1 to be precise ratio I would have had if it was a 2 1/2" pulley like I thought it was would have put me well over 20,000 rpm at that engine speed.