3g Alternator pulleys

TOOLOW91

If you're the village idiot what's that make me?
15 Year Member
Nov 29, 1999
7,398
7,282
234
S.I.NY
Do any of you know where or know of a 3g 6 rib alternator pulley that is 2.75 inches . I know a 94-95 is 2 1/8 . 96-98 v6 is 2.5 inches . I’m looking for something that is 2.75 .

I am looking to put my custom asp 8 inch blower pulley with my 6 inch acc drive to get my water pump moving more water at idle . It will be slightly over spun from a 93 cobra After doing all the math . Where as right now it’s spinning slower then a stock 5.0 car or a 93 cobra car with the 93 water pump pulley and a 4.6 under driven acc drive blower pulley at idle .

The alternator must be addressed as well because at 7200rpm if I didn’t change the pulley it will be on fire at close to 20k rpm with the current 94-95 pulley . If i go to the 2.5inch alternator pulley it’s still a little higher then I’d like at 17,280 . For the split seconds it would live there I don’t think it will hurt it but I’d rather be down around 15k rpm at max rpm .

So that leaves the question of does anyone know if one exists ?


In case anyone was curious . They say are 16k is the limit for failure on the alternator .




Water pump and alternator speeds

4.75inch stock w/p
4 inches 93 cobra

5.2 inch crank pulley cobra
4.6 diameter on Vortech ( 8 inch blower)
4.75 diameter on Vortech (6.87 blower )
6 inch stock mustang


1000 rpm idle Speed
Water pump Speed
Stock 1263 rpm

Cobra 1300 rpm

4.6inch crank 1150 rpm / 6.0 crank 1470rpm

4.75 crank - 1163rpm



5800 rpm
Water pump speed

Stock 7326
Cobra 7540
4.6 inch crank 6669/ 6.0 crank -8700
4.75 - 6887



7000rpm
Water pump speed

Stock 8842 Rpm
Cobra 9100 rpm
4.6 drive -8049 Rpm / 6 inch drive 10,500 rpm
4.75 drive - 8312 rpm



Alternator Speeds
My car 2 1/8 Pulley ( stock 94-95 3g)
2.5 - 96-98 v6 3g alternator pulley

4.6 Crank at 6800 rpm = 14,685 rpm
6.0 Crank at 6800 rpm = 19,154 rpm

4.6 Crank at 980 rpm= 2,116 rpm
6.0 Crank at 980rpm =2,760 rpm

2.5 alt pulley -
4.6 Crank / 6800 rpm = 12411 rpm
6.0 Crank /6800 rpm =16,320 rpm

4.6 crank / idle 980rpm = 1803 rpm
6.0crank / idle 980rpm = 2352 rpm

2.75 alt pulley
4.6 crank /6800 rpm =11,374 rpm
6.0 crank /6800 rpm =14,836 rpm

4.6 crank / idle980rpm =1,683 rpm
6.0 crank / idle 980 rpm =2,138 rpm
 
Last edited:
  • Sponsors(?)


67coupe

Founding Member
Apr 5, 2002
658
409
93
Huntsville, AL
I know from reading all the various cobra forums that alt rpm is a major concern for those that change lower pulley sizes. The go to company for most is Metco. However, those are for 8 rib belts. Maybe give them a call and see if they’re willing to machine a 6 rib in the size you’re after.
 

TOOLOW91

If you're the village idiot what's that make me?
15 Year Member
Nov 29, 1999
7,398
7,282
234
S.I.NY
I know from reading all the various cobra forums that alt rpm is a major concern for those that change lower pulley sizes. The go to company for most is Metco. However, those are for 8 rib belts. Maybe give them a call and see if they’re willing to machine a 6 rib in the size you’re after.
Thank you ! Didn’t even think of metco
 
  • Like
Reactions: 67coupe

TOOLOW91

If you're the village idiot what's that make me?
15 Year Member
Nov 29, 1999
7,398
7,282
234
S.I.NY
Standard 3G pulley is 2.4" (60mm).
Overdrive pulley is 1.75" (44mm).
ASP520004 from Auto Specialties.
I’m not looking to go smaller . I need it to be larger . With a 6 inch crank pulley even at 2.5 it’s still spinning faster then I’d like .

I posted the calculations . For what it’s worth it’s 2.5 inches at th top of my calipers on a 3g pulley for a 96-98 v6 car . P/n - GP685

A 94-95 gt is 2 1/8 (2.13 on the calipers ) p/n -gp712

A lot of mis info out there on the size of these pulleys .What I’m giving you I have physically checked and measured myself . I even burned one up at 20k rpm the first time tried the 6 inch crank pulley I had made ( 8 inch blower ) . Which is what led me to look into what happened realizing I never accounted for the smaller alt pulley at the time .

At that time I had switchwd from a 4.75 crank drive pulley ( 6.87 blower ) to the custom asp I had made . Now I’m going back to the 6.0acc pulley to speed the water pump up but I need to take the alternator into account.

Here is the picture . These are both motorcraft pulleys
 

Attachments

  • DEBD6E0E-9A9E-44DD-8ED5-DDE753214E30.jpeg
    DEBD6E0E-9A9E-44DD-8ED5-DDE753214E30.jpeg
    483.3 KB · Views: 25

TOOLOW91

If you're the village idiot what's that make me?
15 Year Member
Nov 29, 1999
7,398
7,282
234
S.I.NY
I spoke to ASP today . He said he can make me one .
125 in steel and i can have it in 2 weeks
100 in alum and i can have it 4 weeks

If any blower guys ever run into issues and try different things I hope the pulley sizes and rpm stuff helps .
 

KRUISR

Well-Known Member
Apr 16, 2015
388
131
63
50
Just curious, how often and how long are you running at 7000+ rpm?

I looked on rockauto.com and found that the 1998 Ford Contour V6 has a pulley about what you are looking for. I looked under re-manufactured alternators and the ACDELCO ones listed pulley size. Re-man'd had a 2.7" pulley. Under the new alternators, the ACDELCO unit listed a 2.8" pulley. Might be a place to start.

Link to re-man'd

Link to new
 
Last edited:
  • Friendly
Reactions: TOOLOW91

TOOLOW91

If you're the village idiot what's that make me?
15 Year Member
Nov 29, 1999
7,398
7,282
234
S.I.NY
Just curious, how often and how long are you running at 7000+ rpm?

I looked on rockauto.com and found that the 1998 Ford Contour V6 has a pulley about what you are looking for. I looked under re-manufactured alternators and the ACDELCO ones listed pulley size. Re-man'd had a 2.7" pulley. Under the new alternators, the ACDELCO unit listed a 2.8" pulley. Might be a place to start.

Link to re-man'd

Link to new
When the car is finally tuned again and I am out messing around it will see 68-7200 . My concern is not having anything else to worry about more then I already do . I’m sure 1-2 trips there is fine but even if it sees high 16k rpm at 6800 that’s an issue . It’s going to give up at some point . I have experienced it before . When it had the manual still no lift shifting it would go to 7400 sometimes .
 

TOOLOW91

If you're the village idiot what's that make me?
15 Year Member
Nov 29, 1999
7,398
7,282
234
S.I.NY
Just curious, how often and how long are you running at 7000+ rpm?

I looked on rockauto.com and found that the 1998 Ford Contour V6 has a pulley about what you are looking for. I looked under re-manufactured alternators and the ACDELCO ones listed pulley size. Re-man'd had a 2.7" pulley. Under the new alternators, the ACDELCO unit listed a 2.8" pulley. Might be a place to start.

Link to re-man'd

Link to new
Looks like it may work . We’ll see . It’s no longer made . The part number is FOCZ-10344-C or GP-683 on the pulley itself

I got one coming from eBay for 35$.
 

Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
33,909
10,202
224
Massachusetts
I feel like there is a good Excel spreadsheet pulley RPM calculator that never got made that would come in handy here.

but then again how many guys actually calculate out pulley RPM? Not many I bet
 
  • Like
Reactions: 7991LXnSHO

TOOLOW91

If you're the village idiot what's that make me?
15 Year Member
Nov 29, 1999
7,398
7,282
234
S.I.NY
I feel like there is a good Excel spreadsheet pulley RPM calculator that never got made that would come in handy here.

but then again how many guys actually calculate out pulley RPM? Not many I bet
I don’t know if anyone has dug this far Into seeing how far off pulleys spin from the oem designed rpm with different crank pulleys like I am so I have to agree . The lack of info out there is sort of what pushed me to do this and a make a small chart . Not that it’s ground breaking but hey it’s here .
 

KZGUNS

I can swing up to 11”
Jul 23, 2018
734
388
73
44
chardon, Ohio
I don’t know if anyone has dug this far Into seeing how far off pulleys spin from the oem designed rpm with different crank pulleys like I am so I have to agree . The lack of info out there is sort of what pushed me to do this and a make a small chart . Not that it’s ground breaking but hey it’s here .
hmmm I should look into this as well. I'm running a custom crank pulley 6.81" I believe and a stock alternator pulley (8 rib) off a 99 navigator. Never dawned on me that i may be over driving the alt too much. will they give a deal on 2 pulleys if they have to make them?
 
Last edited:
  • Like
Reactions: TOOLOW91

TOOLOW91

If you're the village idiot what's that make me?
15 Year Member
Nov 29, 1999
7,398
7,282
234
S.I.NY
hmmm I should look into this as well. I'm running a custom crank pulley 6.81" I believe and a stock alternator pulley (8 rib) off a 99 navigator. Never dawned on me that i may be over driving the alt too much. will they give a deal on 2 pulleys if they have to make them?
I just tried ordering the contour one Off eBay
to see what happens , it’s worth checking yours to make sure it isn’t over spinning at your shift point .
 
  • Like
Reactions: KZGUNS

7991LXnSHO

Now I want a 10 year badge
10 Year Member
Sep 1, 2010
3,277
662
174
Kearney, NE
So what are good targets for idle and max rpms on the alternator?
And a spreadsheet should be easy to make, my brain is just sprained at the moment.

I don’t know if anyone has dug this far Into seeing how far off pulleys spin from the oem designed rpm with different crank pulleys like I am so I have to agree . The lack of info out there is sort of what pushed me to do this and a make a small chart . Not that it’s ground breaking but hey it’s here .
 

Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
33,909
10,202
224
Massachusetts
So what are good targets for idle and max rpms on the alternator?
And a spreadsheet should be easy to make, my brain is just sprained at the moment.

depends on the alternator. They vary. For your common 3G I think max is 18000 rpm but I forget what full charge RPM is.
 

TOOLOW91

If you're the village idiot what's that make me?
15 Year Member
Nov 29, 1999
7,398
7,282
234
S.I.NY
depends on the alternator. They vary. For your common 3G I think max is 18000 rpm but I forget what full charge RPM is.
I know I could get away with the 16k it will make with the 2.5 pulley but if I can be around 14k and 2100 at idle I like that idea better then being on the edge when I am turning rpm . I think full charge is around 4-6k
 

KRUISR

Well-Known Member
Apr 16, 2015
388
131
63
50
Glad to help. I always look to other OEM parts before I consider having something made. The hunt is fun and very satisfying when you figure out another way to do something.
 

TOOLOW91

If you're the village idiot what's that make me?
15 Year Member
Nov 29, 1999
7,398
7,282
234
S.I.NY
Glad to help. I always look to other OEM parts before I consider having something made. The hunt is fun and very satisfying when you figure out another way to do something.
Yeah man , I wouldn’t have known how to go about it the way you did but it is really appreciated . The only crazy part here is the pulley is no longer made so they are scarce