Underpully's, Alternators, & Me!
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Der Postmeister
Joined: Sep 2006
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From: Long Beach, Calimexiforia
Underpully's, Alternators, & Me!
I had been thinkin about looking into underpully's & remembered something about the stock alternator possibly being problematic. Then, last night. while minding my own business, my Battery light came on & I began discharging! 
So this might be a good time to look a little harder.
What exactly do underpully's do?
Do they affect curb idle?
Do they affect MPG?
Can I or would I want to continue running 16 BTDC?
Stock serpentine still work?
Should I get a higher output ALT. unit or mod it in some other way (pully size)?
How aggressive on the pulleys? Lookin for a little bump. Nothing that could prove problematic?
Benefits/ Are they worth it?
Any potential drawbacks?
There's an auto electric shop I've been going to for over 30 years, back when I had a fleet of trucks. They could rebuild mine to special specs. if need be.
They offer standard grade rebuilds & Lifetime "bulletproof" rebuilds!
So this might be a good time to look a little harder.What exactly do underpully's do?
Do they affect curb idle?
Do they affect MPG?
Can I or would I want to continue running 16 BTDC?
Stock serpentine still work?
Should I get a higher output ALT. unit or mod it in some other way (pully size)?
How aggressive on the pulleys? Lookin for a little bump. Nothing that could prove problematic?
Benefits/ Are they worth it?
Any potential drawbacks?
There's an auto electric shop I've been going to for over 30 years, back when I had a fleet of trucks. They could rebuild mine to special specs. if need be.
They offer standard grade rebuilds & Lifetime "bulletproof" rebuilds!
Postmaster
Joined: Jan 2009
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The underdrive pullys slow the accessories down & can free up as much as 15 hp in the higher RPMs , they wont affect the idle or timing , not sure about mpg , it should help . I use them on my 95 with the stock alt , never had any charging or overheating problems...Lew
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Der Postmeister
Joined: Sep 2006
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From: Long Beach, Calimexiforia
Do the underpullys come in different extremes?
A/C & P/S pump won't have a problem w/ it?
So just replace my pooched alternator w/ the same output?
Postmaster
Joined: Dec 2007
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From: Jacksonville FL
They also make "power and amp" series pulleys so you wont have charging problems.
March Underdrive Pulleys makes good ones.
Ive never heard of any problems with UD pulleys other than a few people having alternator charging problems(without the power and amp pulleys)
March Underdrive Pulleys makes good ones.
Ive never heard of any problems with UD pulleys other than a few people having alternator charging problems(without the power and amp pulleys)
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From: on the garage floor. lol!
i got the march under drive pulleys for my 94 f150 302/5.0l. the back side of the alternator pulley was rubbing on the alternator so i didn't use the set up and its just sitting on the shelf. i called march and talked to a rep and was told that they never heard of anything like that happening before and there should be no problems with the pulley. i think that they didn't do enough r & d for the product. personally i think march sucks a**........
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Der Postmeister
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From: Long Beach, Calimexiforia
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No problem with the water pump or AC , the pullys will help all the accessories last long to , especally on the high reving 302s , after 4000 rpm the stock pullys are just spining everything way to fast when they don't need to . I would google underdrive pullys , there is some good info on the mustang forums about them , i have used them on two mustangs with zero problems , its one of those bolt ons you can feel with your butt o meter.....Lew
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Der Postmeister
Joined: Sep 2006
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From: Long Beach, Calimexiforia
As mentioned my Alternator just pooched. It's a 70 amp. Should I go w/ a 80 or 90 amp, or would it matter regarding the slightly less ATL rpm? I do mostly city stop & go, w/ a lot of time at curb idle (650 rpm). STV mentioned the Power & amp series?
So this will be most effective about where my Timing curve is "all in"? Around 3K. My base time is 16 BTDC. ECU adds 20 degrees +/- 3.
So this will be most effective about where my Timing curve is "all in"? Around 3K. My base time is 16 BTDC. ECU adds 20 degrees +/- 3.
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what size is your current alternator pulley? I've seen them as small as 1-7/8" in diameter, many '80 fullsize passenger cars with the 302 engine have those small pulleys so if what you have now is larger there is a source of small pulleys for ya. Also, when you replace your 70-amp alternator, do not install a direct-replacement unit but instead go for the 3G 130-amp alternator style found on many of the mid-90s Ford vehicles (both cars and trucks), that alone will give you better output at idle even if you don't run the 1-7/8" pulley.
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Der Postmeister
Joined: Sep 2006
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From: Long Beach, Calimexiforia
He had a new Motorcraft 70 amp that would plug & play, but suggested a new Motorcraft 90 amp. upgrade. He said the 90 amp will run considerably cooler & of course more output, but the upgrade is, it comes w/ a harness modification. Evidently, my version is predisposed to engine fires.
90 amp units came stock in dual battery & Tow package Trucks. He also said, while my year 302 lists 40,50,60,70,80, & 90 amp Alternator units as being used, 70's & 90's were the two most in use.
So he said, take the 90 amp home & mount it, drive it the 1 miles back to his shop in the morning & they'd do the harness mod for me for free. $136. out the door! I'm liken it!
I think I'll put the under drive pully's on the back burner, but will keep all the input in mind & thanks everyone for that & about alternator choices.
02, 2007, 5o, alternators, f150, ford, free, good, harley, horsepower, kit, kits, mustang, underpulley, underpully, underpuly
