3g Alternator pulleys

TOOLOW91 · Jul 29, 2020

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

67coupe · Jul 30, 2020

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 · Jul 30, 2020

67coupe said:
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

Blown88GT · Jul 30, 2020

Standard 3G pulley is 2.4" (60mm).
Overdrive pulley is 1.75" (44mm).
ASP520004 from Auto Specialties.

TOOLOW91 · Jul 30, 2020

Blown88GT said:
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

TOOLOW91 · Jul 30, 2020

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 · Jul 30, 2020

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

More Information for ACDELCO 3342261A

Link to new

More Information for ACDELCO 3351116

TOOLOW91 · Jul 30, 2020

KRUISR said:
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

More Information for ACDELCO 3342261A

Link to new

More Information for ACDELCO 3351116

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 · Jul 30, 2020

KRUISR said:
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

More Information for ACDELCO 3342261A

Link to new

More Information for ACDELCO 3351116

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 · Jul 30, 2020

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

CarMichael Angelo · Jul 30, 2020

TOOLOW91 said:
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$.

Input and advice noticeably missing from a certain 2jz swap thread......

TOOLOW91 · Jul 30, 2020

Mustang5L5 said:
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 · Jul 31, 2020

TOOLOW91 said:
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?

TOOLOW91 · Jul 31, 2020

KZGUNS said:
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 .

7991LXnSHO · Jul 31, 2020

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.

TOOLOW91 said:
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 · Jul 31, 2020

7991LXnSHO said:
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 · Jul 31, 2020

Mustang5L5 said:
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

TOOLOW91 · Aug 8, 2020

BIG PROPS !!!! To @KRUISR . Thank you for this find and saving me 100 bucks on having one made .

Left to right

94-95 Gt , 96-98 V6 , ford contour .

KRUISR · Aug 8, 2020

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 · Aug 8, 2020

KRUISR said:
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

3g Alternator pulleys

TOOLOW91

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