SLP Underdrive Pulley,worth it?

**Whiteboycntdnce** · 01-26-2008, 04:19 AM

I'm ordering a cam/oil pump/double roller timing set... Is it worth the money to buy an underdrive pulley? Ive heard both good and bad thingsabout it.

**FuhBreezeE** · 01-26-2008, 04:32 AM

Gained 7rwhp up top from my ASP UD Pulley.

**nhraformula** · 01-26-2008, 05:42 AM

cost to h.p ratio, i say no

**9t8z28** · 01-26-2008, 06:50 AM

Originally Posted by nhraformula

cost to h.p ratio, i say no

X2. Around $300 for a couple of horsepower

**shady milkman** · 01-26-2008, 07:00 AM

the bad comes from the fact that alot of the ud pulleys dont have harmonic balancers like the stock ud pulley. so without the harmonic balancer the ud will cause vibrations that will eventually crack the block/ and or stress the block on a microscopic level. where most of the money comes from for the slp ud pulley is the harmonic balancer that is built inside the ud pulley...that and its slp. so i would suggest if you get a ud pulley make sure it has a built in harmonic balancer ...better safe then sorry.

**Mr. Luos** · 01-26-2008, 07:01 AM

ASP balancer on mine.

Not much power to be gained, but I have no problems with mine.

I wouldn't buy much from SLP though.

**Z28LS1** · 01-26-2008, 09:56 AM

I bought my UD pulley from a fellow ls1 owner. I mainly bought a weliand intake manifold, but he said he'd throw in a UD pulley if i payed full price. (350) so i said yeah, but ive heard worse and worse things. They say UD pulleys cause all your rotation to move too slow (down at lower RPMs).. which means your alternator, water pump, power steering.. etc has to work harder. So im risking the life of these components and my steering is a little more sluggush.... So if you plan on racing ur car instead of a daily driver.. it guess its not bad.. i heard dynos of 8rwhp a few times. And just for the record, I have no problems with it yet (3000 miles) but its on the back of my mind. good luck

**99Ls1fever** · 01-26-2008, 10:06 AM

Originally Posted by nhraformula

cost to h.p ratio, i say no

Fully agree....

**Speed Psychosis** · 01-26-2008, 12:18 PM

it will under power your electronics/lights at idle. If radio and everything is stock it might not make a difference though.

I'd get a lid, headers, a catback, or a new gear ratio since those make a bigger difference per $$$.

**shady milkman** · 01-26-2008, 01:38 PM

let us not also forget that a ud pulley improves throttle response and more importantly...cuts rotational mass...which is huge for improved times ect.

**Firebirdjones** · 01-26-2008, 02:03 PM

I've posted enough on these, so I think my view is known.

But I personally don't like them. They are expensive no matter where you go considering the HP you might gain.

The SLP is a better design than the ASP pulley. SLP uses a deeper groove for belt retention,,,something ASP doesn't have at all.

I don't like the fact that my car runs hotter around town with this pulley, it has slowed my water pump down to the point where the fans don't shut off at all when I sit in traffic. The water simply moves too slow,,,,once the engine comes up to about 1300 rpms the fans shut off within 30 seconds,,,,,,
so the cooling issue can be a real problem for me,,,especially moving to Arizona soon.

At night the lights dim all the time while idling,,,I've bumped the idle speed a pinch in the tune (you can only go so far with it before causing other issues) but it was no real help anyway. The low voltage hasn't been a real issue, other than driving me nuts,,,,and I have the stock stereo and all.

The power steering is a small issue too,,,,moving around in parking spots, in and out of the garage while idling around the pump is running so slow that you can feel a chatter in the steering wheel that bugs me as well.

If there is a HP gain it's so small you won't notice it. The engine doesn't rev faster at all that I notice,,,and at the track I had a before and after comparison,,,,the car ran the same ET and MPH,,,there was no change or advantage that the time clocks noticed.

As far as I'm concerned I could find 10 other things to spend $300 on that would actually net me some ET and MPH.

It's good for a door stop,,,thats about it.

**99Ls1fever** · 01-26-2008, 03:39 PM

Originally Posted by Firebirdjones

I've posted enough on these, so I think my view is known.

But I personally don't like them. They are expensive no matter where you go considering the HP you might gain.

The SLP is a better design than the ASP pulley. SLP uses a deeper groove for belt retention,,,something ASP doesn't have at all.

I don't like the fact that my car runs hotter around town with this pulley, it has slowed my water pump down to the point where the fans don't shut off at all when I sit in traffic. The water simply moves too slow,,,,once the engine comes up to about 1300 rpms the fans shut off within 30 seconds,,,,,,
so the cooling issue can be a real problem for me,,,especially moving to Arizona soon.

At night the lights dim all the time while idling,,,I've bumped the idle speed a pinch in the tune (you can only go so far with it before causing other issues) but it was no real help anyway. The low voltage hasn't been a real issue, other than driving me nuts,,,,and I have the stock stereo and all.

The power steering is a small issue too,,,,moving around in parking spots, in and out of the garage while idling around the pump is running so slow that you can feel a chatter in the steering wheel that bugs me as well.

If there is a HP gain it's so small you won't notice it. The engine doesn't rev faster at all that I notice,,,and at the track I had a before and after comparison,,,,the car ran the same ET and MPH,,,there was no change or advantage that the time clocks noticed.

As far as I'm concerned I could find 10 other things to spend $300 on that would actually net me some ET and MPH.

It's good for a door stop,,,thats about it.

lol that is funny, but soooo true...

**Speed Psychosis** · 01-26-2008, 07:04 PM

Originally Posted by shady milkman

let us not also forget that a ud pulley improves throttle response and more importantly...cuts rotational mass...which is huge for improved times ect.

but upgrading maf or throttle body improves response too. As well as flywheel which is pretty much results of pulley without the bad effects of under driving.

**99Ls1fever** · 01-26-2008, 09:40 PM

underdrive still cost to hp ratio and damage to correct ratio from gm....

**180ls1** · 01-26-2008, 10:26 PM

Originally Posted by shady milkman

let us not also forget that a ud pulley improves throttle response and more importantly...cuts rotational mass...which is huge for improved times ect.

exactley it is like an aluminum flywheel, i had one installed they do not do much for rwhp put it gets intop the power band a good amount quicker.

But i would say hold off on the up pulley untill you run out of mods to do to your car or unless you find a really good deal.

**99Ls1fever** · 01-27-2008, 10:40 AM

Originally Posted by 180ls1

exactley it is like an aluminum flywheel, i had one installed they do not do much for rwhp put it gets intop the power band a good amount quicker.

But i would say hold off on the up pulley untill you run out of mods to do to your car or unless you find a really good deal.

where did you get your flywheel at and do you have a link?

**shady milkman** · 01-27-2008, 10:49 AM

lets not forget the alternator pulley. i am pretty sure that they should be used together. but however you can not argue the fact that any decrease in rotational mass is a big benefit. also firebird i dont know man..maybe the ud pulley isnt good for dd cars ..i am sure tho that in race applications the ud pulley+alt pulley would be extremely benefital

**Firebirdjones** · 01-27-2008, 02:02 PM

Originally Posted by shady milkman

lets not forget the alternator pulley. i am pretty sure that they should be used together. but however you can not argue the fact that any decrease in rotational mass is a big benefit. also firebird i dont know man..maybe the ud pulley isnt good for dd cars ..i am sure tho that in race applications the ud pulley+alt pulley would be extremely benefital

Ya for a race car it would be a good idea. Actually on the race car I had I ran an electric water pump, there were no belt driven accessories at all on it.

**Firebirdjones** · 01-27-2008, 02:08 PM

Originally Posted by 99Ls1fever

where did you get your flywheel at and do you have a link?

I use an aluminum Fidanza on mine. Actually I didn't put it on for recipricating weight reasons. I installed it because it was time for a clutch job,,,,and the shop I use to use for resurfacing flywheels went out of business. The next closest place was on the other side of town 45 miles away so I decided screw that....I couldn't afford the down time waiting for my flywheels so I ordered an aluminum Fidanza for the sole pupose of being able to remove the clutch surface area and bolt in a new one.

With the Fidanza no resurface is necessary,,,,before your clutch job just get another steel plate and when you tear the car down it's just a simple R&R job. No resurface necessary,,,,car is down for 2-3 hours and your done.

I honestly don't notice any perfomance difference with it,,,but I can tell you my clutch jobs are much quicker and less painfull now.