scorp508

I picked up a single crank underdrive pully last night for $25. :) Hey why not, ya know?

I already removed my AIR pump, and I'm not going to buy/install an alternator pully just to stress it out more (I say that now).

What are we talking here at best to the wheels? I'm not expecting much at all (if anything), the price was right, so I took it.

BADMUDE

The only question I have about it is how will it affect cooling? The water pump will turn slower, thus slower circulation?

I know when it get 100º+ down here..I need all the circulation I can get..:)

scorp508

It slows accessory rotation by 30%. I'm not overly worried on cooling, as the mobil 1 runs cooler in the first place. Also my fans come on very soon and there is a 160 thermo in it.

65Z01

Based on an earlier thread on differences between Net & Gross HP ratings I'd guess about 5-10hp gain from an underdrive crank pulley.

BTW, I have the March underdrive crank pulley only installed:
1) while sitting in line at the strip I have to run my engine at about 1,000rpm or so to maintain 155deg F coolant temp.
2) with accessories on the voltage drops to about 12Vdc.
3) I didn't measure any trap speed increase but was having ESC problems at the time.

h rocks

Scorp, go ahead and swap it. (You may need a smaller belt.) As long as you don't run the alternator underdrive pulley with it, you won't have any issues. I've run both before, and if you don't do a lot of highway driving, you would have a battery charging problem. I have never encountered any issues running just the crank pulley.

scorp508

Ut oh. :) I do about 600 miles of highway driving a week.


65mph = 1850 RPM
80 mph = ~2300 RPM

65Z01

Above say 1k RPM you should still see 13.5Vdc.

dgoodhue

I have one. I currently use just the Crank pulley. When I use my stock chip and small alternator pulley, I have problem with the low voltage light comeing on, if idle a lot. With my aftermarket chip (and it 100rpm higher idle) I don't have a problem. I can't remember if I have tried using the stock chip with stock alternator pulley. I personally don't think there is much of a gain with a L98 underdrive pulley, I sure didn't feel it.

john25

March Performance makes a Power & Amp series set. It's a crank, water pump & alt pulley set but the alt pulley is smaller than stock to keep charging where it should be. Works great, I have never had cooling problems even with a modified motor, YET. As for the one crank pulley I'd say go ahead a swap it. Hey, for the money it's worth a try.

85vet

Scorp,
Just remember, Do not believe everything you read.

I have the underdrive pulleys on and my alternator.Volts is fine. My cooling at idle is fine too.

For a 20 min job even if it is only 1 hp it is definately worth it when you put it all together.