Underdrive Pulleys

**tommyjt2006** · 11-28-2007, 06:11 AM

Can anyone recommend an underdrive pulley? I have read about the ASP pulley with the alternator pulley and I also read about another one on this thread a while back and don't remember what the name of it was. Everytime I try to buy an ASP they are on back order. Thanks. -Tom.

**Kamauxx** · 11-28-2007, 07:14 AM

I got an ASP. Works fine. The guy that installed my cam gave it to me and installed it cause he was having trouble getting the stock pulley back on...so I have no idea who would be a good company to buy one from.

**Firebirdjones** · 11-28-2007, 10:52 AM

ASP is a popular choice,,,another one to look at would be SLP's underdrive setup,,,,It actually looks to be a little better quality,,,,since it has a deep groove made into the pulley for a little extra insurance.

Although I have never had a problem throwing the belt on the ASP pulley I currently run,,,I really don't like it for many reasons,,,would take me forever to explain.

I plain to remove it sometime in the future and sell it. I just haven't gotten around to working on the car lately, just too busy.

**Sunset T/A** · 11-28-2007, 01:53 PM

I have the SLP and it works fine. Really good quality.

**tommyjt2006** · 11-28-2007, 02:07 PM

My true goal is to free up some horsepower and gain a tenth or so....? Is there a true gain from these pulleys? Thanks. -Tom.

**Firebirdjones** · 11-28-2007, 02:27 PM

Originally Posted by tommyjt2006

My true goal is to free up some horsepower and gain a tenth or so....? Is there a true gain from these pulleys? Thanks. -Tom.

Some claim it's worth a tenth. For my car it didn't do squat. I installed it and went back to the track with nearly same DA numbers and running the same 60 foot times,,,,the cars ET and MPH didn't change one tiny bit.

In my opinion for the money they get for a pulley it's a waste of money. I can think of many other things to spend $200 or more on and pick up at least a tenth or more.

What the pulley did do is lower my alternator voltage to the point that it dims the lights at night,,,I even bumped the idle up slightly with HPtuners,,,,but that really didn't help any. Not a big deal to most but I don't like it.

It also made the car run warmer since it slowed the water pump down. With the 160 thermostat and fans programmed (on at 182 and off at 180) with the stock pulley this worked excellent.
Now with the underdrive the fan never shuts off while idling around,,,,pretty sad the fans can't pull the temp down a measly 2 DEGREES because the water pump is too damn slow. The fans will shut off if I click it up in neutral and hold the motor at about 1500 rpms,,,then it cools down,,,but if you let it idle in traffic, parking lot or even putting around slowly they just keep running continuously.

This is what I won't put up with so the pulley is coming back off. I would rather have the engine run a little cooler and have the fans cycle in a normal fassion without worrying rather than gain single digit HP that I couldn't even notice at the track.

If you want to save your money and give me some time to remove it I will gladly sell it. Can't guarantee when I will get to it though,,,very busy for a while,,,but eventually it will be in the classifieds here.

**allforspeed** · 11-28-2007, 08:58 PM

i got a powerbond one, same exact piece as teh SLP, 25% under drive, got it for 200$ with bolt and belt on a sponsor sale on here, didn't notice a difference, but you probably wouldn't notice 8hp on a 350hp either, it helps from cooking the power steering pump during auto cross or any racing you do though and will help keep your accessories from getting messed up from sustained high rpm racing, i have noticed no problems charging or cooling under any situation, even with everything in the car on all at once to test it, i have the stock stereo though, seems like it revs a little easier but hard to say, seems like it may have increased my mpg 1 or 2 also. very small difference, only reason i did it was to help from ruining my power steering while auto x, dont expect to notice a difference, if i was after HP i would probably save the 200$ toward a cam or some headers or something

**cocheesews6** · 11-29-2007, 09:13 PM

From what I've read, pulleys work well with other mods involved and a tune. I just ordered a Powerbond like mentioned above, and hoping it works well.
Thats good to know about the auto cross too.

**Empatho** · 11-30-2007, 12:30 AM

I have a mach performance ud pulley and I noticed that it revs up faster, my volts dropped but not by allot the only problem I had with it is that it was a b!t<h to install If I was to do it again I would get the SLP one just because of the intallation

**Firebirdjones** · 11-30-2007, 03:43 AM

Originally Posted by cocheesews6

From what I've read, pulleys work well with other mods involved and a tune. I just ordered a Powerbond like mentioned above, and hoping it works well.
Thats good to know about the auto cross too.

Ya,,,I have other bolt ons and a custom tune as well,,,,but it still didn't do anything for my car except cause the fans to run continuously

**JonB** · 11-30-2007, 08:00 AM

Originally Posted by Firebirdjones

Ya,,,I have other bolt ons and a custom tune as well,,,,but it still didn't do anything for my car except cause the fans to run continuously

You need better fan settings. 182 on 180 off is no good. How long does it take water at 180 to warm back up to 182? Not long maybe a few seconds. I would think your fans would be kicking on and off constatnly at idle with that setting.

Heres a good setting for a 160 stat.
________160
________ON______OFF
F1______184F____175F
________84.4C___79.4C
F2______194F____185F
________90C_____85C

As for the original topic, I run an asp. I did't notice any huge power difference but I throw it into the every bit helps catagory. When I did the pulley it was origanally going to be my last mod. I had no plans to go into internal motor mods so I figured I would put a pulley on to finish the external mods off. The only time I see my voltage drop is at night with everything running, lights, a/c, fans ect it will drop just below 13 at idle then go right up past 13 while driving.

**Firebirdjones** · 11-30-2007, 11:12 AM

Originally Posted by JonB

You need better fan settings. 182 on 180 off is no good. How long does it take water at 180 to warm back up to 182? Not long maybe a few seconds. I would think your fans would be kicking on and off constatnly at idle with that setting.

Heres a good setting for a 160 stat.
________160
________ON______OFF
F1______184F____175F
________84.4C___79.4C
F2______194F____185F
________90C_____85C

As for the original topic, I run an asp. I did't notice any huge power difference but I throw it into the every bit helps catagory. When I did the pulley it was origanally going to be my last mod. I had no plans to go into internal motor mods so I figured I would put a pulley on to finish the external mods off. The only time I see my voltage drop is at night with everything running, lights, a/c, fans ect it will drop just below 13 at idle then go right up past 13 while driving.

Thanks for the input but those fan setting you have won't work on my car.

Actually the fan setting I currently have worked perfectly with the stock crank pulley. They never ran very long and when the engine temp was below the on temperature,,,it took forever for the engine to come back up to 182 where the on temperature is,,,,,so they actually barely ran much at all.

Now with the pulley as long as the car is moving it's fine,,,engine rpms are up and water is circulating fine. But as soon as you come to a stop the fans come on. The temperature will stay at 182 and never come down. If I set the on temp higher as I have tried,,,,,at 185 degrees,,,,the engine will just stay at that temp and never come down. So it's not really a matter of where I have the On temperature set,,,,,it's a matter of the pulley simply not turning the water pump fast enough while setting still,,,,,It just won't cool it. Keeping in mind I am not in that hot of a climate either,,,,only hits mid 90's here in the summer usually,,,,I would hate to think how it would act in Arizona or somewhere much hotter. I consider it lucky that the fans can atleast hold the motor where ever I set the fans, however it's scary to think that any hotter climate could cause the engine to keep climbing past the fan settings,,,,yikes!

With that said there is also another problem that compounds this. These thermostats on the LS1, although rated to work at the 160 degree mark,,,actually they do not. While scanning I can watch the thermostat open and that doesn't accur until 173 degrees and it more than likely isn't fully open until about 175 degrees. While cruising steady state down the road on a cold day, no fans running, the engine will stay at about 176-177 degrees, where the thermostat is fully open and functioning. This is why I say I cannot use your fan settings,,,,having the off temperature at 175 degrees,,,,the fans will never shut off,,,as there is simply no way they can pull the motor down that cool, the thermostat will not let that happen.

This is why I mentioned here before that it's very important to have a scanner on the car after the thermostat install and find the happy spot where the thermostat is going to run before even touching the fan settings.

Unfortunately due to their design, the LS1 thermostat will not operate in the 160 range. They are simply modified thermostats with a 1/8 inch spacer installed to make them operate at a cooler temp. Spacing them any more for a cooler temp does not allow them to close fully, and this causes other problems. Because of this,,,,although they are said to be 160 thermostats, they actually operate in the mid 170 range. This is the way they have been for a long time. Now that doesn't mean that someone has finally redesigned a new thermostat that actually operates cooler,,,but it would be nice. I haven't researched it any further.

**xzaero0** · 12-01-2007, 10:18 AM

Did the SLP pulley and the electric water pump at the same time. This did make a noticeable diference in power. So I cannot say that the pulley or the pump made a diffence on there own. I have had no problems with my engine running warmer but my volts went down a little, just turned my idol up with a predator and it runs great.

**Firebirdjones** · 12-01-2007, 11:15 AM

Originally Posted by xzaero0

Did the SLP pulley and the electric water pump at the same time. This did make a noticeable diference in power. So I cannot say that the pulley or the pump made a diffence on there own. I have had no problems with my engine running warmer but my volts went down a little, just turned my idol up with a predator and it runs great.

Good to hear it's working to your satisfaction. I also tried turning my idle up with HPtuner,,,problem is you can't go too high or the IAC counts get too high and screwy things start happening. About 100-150 rpms is as far as I care to go,,,and it wasn't enough to really make a difference in voltage readings or temperature problems.

The electric water pump is helping your cooling a great amount,,,,since it is not relying on the underdriven pulley anymore,,,,so you are getting maximum coolant flow even while the engine is idling, which would explain no cooling issues for you.

I on the other hand do not. And I am not willing to relegate the cooling duties to an electric pump that could leave me dead without warnings.