UnderDrive Pulleys

BANGERSTANGER76 · Dec 7, 2011

Guys,

I have a set of underdrive pulleys on my car. They seem to be performing ok. But I wanted to ask what do you all think about them? Do you use them? Do you recommend them? I have since heard about a few isssues and I dont want to cause any problems under there. Let me know your thoughts

Thanks
Banger

Noobz347 · Dec 7, 2011

Buy pulleys for engine bay dress up... not HP.

VibrantRedGT · Dec 7, 2011

I had pulley's on my 347, didn't like that the alternator pulley was small and sometimes at idle during dark the headlights would dim. Probably should have just switched back to the stock pulley's. There's not a huge HP difference between the two, it's not something you can feel.

BANGERSTANGER76 · Dec 7, 2011

VibrantRedGT said:
I had pulley's on my 347, didn't like that the alternator pulley was small and sometimes at idle during dark the headlights would dim. Probably should have just switched back to the stock pulley's. There's not a huge HP difference between the two, it's not something you can feel.

This is exactly what I started this thread to hear.
I dont want a basically useless modification to disturb and thing else under the hood especially electrical. I definately dont real feel the extra power and I dont want to ruin my alternator or anyhting ellse under there. Kind of leaning towards taking them off or maybe just leave the water pump underpulley on. We'll see based off of the replies I get.
Thanks for ressponding bro. Appreciated.

N8Dogg98 · Dec 7, 2011

They will provide a minor boost in accelleration due to the decreased effort in spinning the accessories. I've had them on my car for years and don't have an issue. I also don't experience any dimming of the headlights at night probably because I have a good battery and a healthy alternator.

FastDriver · Dec 7, 2011

They're worth every penny on a car with a 3G alternator like yours. From the dynos I remember seeing back in the 5.0 days, they picked up anywhere from 6-10 rwhp. Running your alternator slower is not going to damage it. Hell, it might even reduce wear to an extent. If your parts are healthy, they won't cause an overheating issue, or an electrical problem.

You might be concerned about things you hear on the fox-body 5.0s, which did not have the 3G alternators. Those cars could barely pump the power needed to run everything stock. That's why the police interceptors came with the upgraded alternators, and why you'll hear people having problems running down their battery at idle when they put pullies on the car. The difference is, those alternators only made 85 amps stock. Yours pushes 130. So, even at a 20% underdrive, you should still be making well more than the old cars did.

BANGERSTANGER76 · Dec 7, 2011

FastDriver said:
They're worth every penny on a car with a 3G alternator like yours. From the dynos I remember seeing back in the 5.0 days, they picked up anywhere from 6-10 rwhp. Running your alternator slower is not going to damage it. Hell, it might even reduce wear to an extent. If your parts are healthy, they won't cause an overheating issue, or an electrical problem.

You might be concerned about things you hear on the fox-body 5.0s, which did not have the 3G alternators. Those cars could barely pump the power needed to run everything stock. That's why the police interceptors came with the upgraded alternators, and why you'll hear people having problems running down their battery at idle when they put pullies on the car. The difference is, those alternators only made 85 amps stock. Yours pushes 130. So, even at a 20% underdrive, you should still be making well more than the old cars did.

Thanks bro.
This really makes it much clearer for me.
When I installed them I was told it was for extra horses and I did it becasue it seemsed like a minor and easy mod. Which is what I wanted. Then I started hearing about nagging issues. But it only makes sense. I have new alternator and waterpump so I should be fine. Ill leave it alone. Its running great and I havent had any issues. Thanks again.

toyman · Dec 8, 2011

VibrantRedGT said:
I had pulley's on my 347, didn't like that the alternator pulley was small and sometimes at idle during dark the headlights would dim. Probably should have just switched back to the stock pulley's. There's not a huge HP difference between the two, it's not something you can feel.

Actually a smaller pulley spins the alternator faster to compensate for the smaller crank UD pulley. IIRC an alternator can be built to deliver full output at idle speeds.

BANGERSTANGER76 · Dec 8, 2011

I'm learning alot. Thank you boys for sharing the knowledge.

BANGER

revhead347 · Dec 11, 2011

I run an underdrive crank and alternator pulley. Never had any significant problem with the alternator. It drops in voltage a little at idle, but not below battery voltage. I usually drops from 14.4v to just over 13v. I did keep the stock water pump pulley, because the water pump did spin a little too slow. My car idles around 900rpm.

Kurt

UnderDrive Pulleys

BANGERSTANGER76

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Noobz347

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VibrantRedGT

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FastDriver

I was uncomfortably high & wearing a helmet

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Apparently my ex-husband made that mistake.

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