What is the best Pulley system?

[Firehawkws6]

I bought the BBK aluminum underdrive pulley and placed it on the crank hub. Easy installation with the new belt, BUT...my voltage dropped when the car is at idle.

I've read on some previous posts that I may need the alternator overdrive pulley to compensate for the loss in voltage. I have also read that the horsepower gains aren't worth it and I should scrap it altogether. I'd hate to scrap this $65.00 pulley and I would love to gain whatever horsepower possible (even if it is small).

What is the best advice for keeping the pulley and fixing the voltage problem? Can the engine run safe with this low voltage? Advice is welcome, thanks!

[ShowNoMercy]

Ditch it, try to recoup some money.

[Firehawkws6]

Why ditch it?

[Racy Roadmaster]

It all depends how much voltage that you lost in your system. An old
NHRA stock and super stock class trick was to use a larger alternator
pulley on their cars,so the alternator would create less parasitic drag
on the overall system.So in theory it does work. I run a larger alternator
pulley on my Roadmaster LT1 (APPROX 15% UNDERDRIVE) without any problems. Also unless you are using an electric water pump you
will be underdriving your water pump also,which may be problematic in the summer. As far as engine HP goes,an underdrive pulley system isnt going
to give you more than a couple HP gain.ed

[steveo]

Originally Posted by Racy Roadmaster

...Also unless you are using an electric water pump you will be underdriving your water pump also,which may be problematic in the summer....

you're definitely thinking of another engine

the lt1 uses a shaft drive waterpump, and will work the same regardless of whether the accessory belt is even on the car or not

definitely not affected by an underdrive pulley

[Firehawkws6]

Im running a Chrome alternator from Jegs in my car 140 output, Tuff Stuff 8173NA Tuff Stuff Chrome Alternators

It should be fine with the underdrive pulley I think. The voltage drops from 13+ to a tad over 12. I just want to be safe and make sure it can handle that lack of charge.

[Racy Roadmaster]

Originally Posted by steveo

you're definitely thinking of another engine

the lt1 uses a shaft drive waterpump, and will work the same regardless of whether the accessory belt is even on the car or not

definitely not affected by an underdrive pulley

Jan 2, You are correct,I was thinking of a different engine. At least I got my mistake for the year overwith really fast! ed

[steveo]

Originally Posted by Firehawkws6

It should be fine with the underdrive pulley I think. The voltage drops from 13+ to a tad over 12. I just want to be safe and make sure it can handle that lack of charge.

just being 12v at idle wouldn't concern me, the car will run, everything on your car is designed to operate with something like 11 to 15 VDC, but if it drops over a longer period of time at idle with electrical load you're asking for trouble.

so, be safe then; go start your car, put a voltmeter on it at the battery. turn your high beams and defroster on. run it for 5 minutes, check the battery voltage. run it for another 20 minutes, check again.

if it isn't holding stable @ 12 volts after 25 minutes, get that pulley off of there or you're asking for trouble

cranking batteries really dont like to be discharged past 12 volts on a constant basis with load put on them, it weakens them. if you really insist on running a car that's undercharging at idle, you'd better get a really nice deep cycle battery, like an optima.

[Firehawkws6]

Thanks Stevo! Great idea, I'll give that shot and see what voltage I'm pulling after running a lot of components.

[Mystery Bird]

Most underdrive pullies are designed to work with a higher idle. People don't realize this and have trouble. The piggy back one is completely worthless as far as performance goes.

[Viper]

None

Drivetrain Modifications #2

[bufmatmuslepants]

Originally Posted by Mystery Bird

Most underdrive pullies are designed to work with a higher idle. People don't realize this and have trouble. The piggy back one is completely worthless as far as performance goes.

Ive been crucified for this before, but I dont even run a balancer, just the underdrive pulley bolted straight to the crank snout. Revs noticeably faster, if I hadnt gotten the pulley for free, I would have skipped it all together tho.

[Racy Roadmaster]

Originally Posted by bufmatmuslepants

Ive been crucified for this before, but I dont even run a balancer, just the underdrive pulley bolted straight to the crank snout. Revs noticeably faster, if I hadnt gotten the pulley for free, I would have skipped it all together tho.

Well the only thing I can say is the balancer has a purpose,and at least
what I have read is that the balancer is supposed to help keep the
crankshaft from vibrating at higher RPMS and reduce harmonics.
If I were you ,I would keep a spare short block or at least a rotating assembly in your personal stock. ed

[bufmatmuslepants]

Oh I know it has a purpose, it is to reduce harmonics. Im going to put it back on, but wanted every last hp for Street Stock class racing.

As far as charging issues, Ive never had a single one. From dailying in traffic, to long highway trips in 6th gear, never ever had any sort of charging issues.

[Firehawkws6]

I increased the idle screw and she runs perfect now. Problem solved!