New LS1 Owners - Newbie Tech - worth it to add ud pulley

My car makes 399 rwhp (Mods in sig)- Id love to give it that extra bump to go over 400, but i really doubt i would actually feel the difference adding an underdrive pulley. I have an asp 25% pulley i got a while back,just not sure i want to spend the $ for a few hp's. What would be a good estimate of hp gain on a car with these mods?

To me, it's not bad for the money, should net you around 5-10rwhp give or take a few

If you have the pulley, what would you have to spend $ on, the install?

If you have the pulley, what would you have to spend $ on, the install?

exactly

another thing to consider, try a different dyno, maybe it will net you over 400. OR dyno your car at the same place on a colder day. If you're looking for a graph that shows over 400, do that.

I don't know how busy your life is but how come you couldn't install it yourself? I would do it but I'm one of those every little bit counts kind of guy lol

I have a full time job and also run a side business online from home--and all that while 3 screaming kids run around me.... so yeah i have no time. The $ it will cost would just be labor. I guess i should at least find out how much it will run and then think it over-- if i could get 5 or so hp i guess thats not to bad.

Definatly worth it. If you really don't have time to install yourself, most shops should be a me to do it for about 1 hr labor charge. Usually $60-$80 depending on the shop. 5-10 rwhp for under $100; not bad.

It's a good bang for the buck mod. You could probably find another car guy near you that would install it for you in under an hour for a few bucks or some beer. It is an easy install!

Free labor when you do the cam, very much worth it. Every little bit helps and does add up.

Definatly worth it. If you really don't have time to install yourself, most shops should be a me to do it for about 1 hr labor charge. Usually $60-$80 depending on the shop. 5-10 rwhp for under $100; not bad.

are you including the cost of the pulley??

He already has the pulley Mark, unless you're making a point that went over my head.

If I do a UDP (which I probably will along with a cam) I'm definitely going to get an ODP for the alternator to keep that thing working properly, that's something to consider.

He already has the pulley Mark, unless you're making a point that went over my head.

If I do a UDP (which I probably will along with a cam) I'm definitely going to get an ODP for the alternator to keep that thing working properly, that's something to consider.

ohhh i missed that lol. but my point is that if you have a shop install the pulley it might not be worth it.

Mike, if you did an overdrive pulley wouldn't that negate the purpose? the point of the udp is to help the motor w/ all accessories to run more free. an overdrive pulley on the alternator would bring you back to square one but you'd have a lighter wallet. someone can correct me if im wrong.

For me it would be something that I would have done the next time the car went in for work. Most of the time it is a pretty simple install but you can search to find that a lot of people have had problems switching pullies. I would also upgrade the alternator pulley especially if you are running aftermarket amps.

I swapped mine on, didn't take long at all.

Didn't notice a huge difference driving but the car definitely revved a little quicker after. Also my track times improved.

ohhh i missed that lol. but my point is that if you have a shop install the pulley it might not be worth it.

Mike, if you did an overdrive pulley wouldn't that negate the purpose? the point of the udp is to help the motor w/ all accessories to run more free. an overdrive pulley on the alternator would bring you back to square one but you'd have a lighter wallet. someone can correct me if im wrong.

No sir, since you are only overdriving one of the accessories. Now if you put an overdrive on all of them then you would be back at square one i suppose. The UDP are usually a little lighter then the stock ones as well. I just did one with motor out of the car and its easy, just make sure you use an ls7 crank bolt(less than 10 bucks I think) or another longer bolt to pull the new pulley on. Using the stock one is dangerous as it only gets a few threads in to pull on.

No sir, since you are only overdriving one of the accessories. Now if you put an overdrive on all of them then you would be back at square one i suppose. The UDP are usually a little lighter then the stock ones as well. I just did one with motor out of the car and its easy, just make sure you use an ls7 crank bolt(less than 10 bucks I think) or another longer bolt to pull the new pulley on. Using the stock one is dangerous as it only gets a few threads in to pull on.

thanks for clearing that up i was a little unsure.

i avoid using a bolt to get the balance on all together, i have one of the install tools and it was the well worth the money. no headaches or worries about stripped threads and only took 30 seconds.

I guess i assumed it was much more labor than you guys are saying- If its just 100 bucks or so, then thats not bad at all for the gain. I do have 2 amps mounted in the car- so i will more than likely get the alt pulley to help out.

If you are searching to break that magic number, this will do it for you. However are there not issues with lights dimming at idle ect with 25% UD?

If you are searching to break that magic number, this will do it for you. However are there not issues with lights dimming at idle ect with 25% UD?

he can always have his idle raised if thats a problem.


and yes, its worth it.

he can always have his idle raised if thats a problem.


and yes, its worth it.

The way I've always understood tuning is that if you are adjusting idle to fix another issue then you are band aiding it and just putting off actually fixing it

I guess i assumed it was much more labor than you guys are saying- If its just 100 bucks or so, then thats not bad at all for the gain. I do have 2 amps mounted in the car- so i will more than likely get the alt pulley to help out.

yep youve got the right idea, definitely get the overdrive for the alt if you have extra electronics in the car.

If you are searching to break that magic number, this will do it for you. However are there not issues with lights dimming at idle ect with 25% UD?

some guys do, some dont, stock you can get away with it, but if you have extra electronics I would absolutely get the alt overdrive which the OP plans on doing.

The way I've always understood tuning is that if you are adjusting idle to fix another issue then you are band aiding it and just putting off actually fixing it

I would agree with this, seems silly, when a lil overdrive thats easy to put on fixes it right.

You'll gain close to 10rwhp. I know of shops that charge 300 for a pulley and install. So around $100 for an install.

The way I've always understood tuning is that if you are adjusting idle to fix another issue then you are band aiding it and just putting off actually fixing it

youre just raising your idle to get a full charge. theres nothing being band aided.

a tuner told me ASP even recommends having your idle raised. ive never had a problem in over 10 yrs.

youre just raising your idle to get a full charge. theres nothing being band aided.

a tuner told me ASP even recommends having your idle raised. ive never had a problem in over 10 yrs.

I dont think its a band-aid but i think im just gonna order the alt pulley instead and try that 1st. I dont want my idle raised - I love to hear my cam lope ;) If i idled it up a little it seems like i wouldnt hear it as much lol.

I dont think its a band-aid but i think im just gonna order the alt pulley instead and try that 1st. I dont want my idle raised - I love to hear my cam lope ;) If i idled it up a little it seems like i wouldnt hear it as much lol.

if youre a manual then i dont think you need to have it raised. even so, its not enough to be concerned with.

If you want the car faster then I would do it, but I wouldn't do it just for dyno numbers. A dyno is an arbitrary tool, every one reads differently and can even vary by temp or location. If you try a different dyno you might be over 400 or way under.

I would do it. You will feel the car rev up to your powerband quicker and with all things being equal, gain 5-7rwhp. This is what I have witnessed.

If your not running an amp with subwoofers there is really no need for an overdrive on the alternator IMO.

If you want to consider trying to do it yourself there is a tool for putting the crank pulley back on with out risk of stripping the bolt.

http://www.coloradospeed.com/index.php?main_page=product_info&cPath=3654&products_id=10976

It actually wouldn't be hard to back one with just some threaded rod and a nice size washer and bolt even.

If your not running an amp with subwoofers there is really no need for an overdrive on the alternator IMO.

If you want to consider trying to do it yourself there is a tool for putting the crank pulley back on with out risk of stripping the bolt.

http://www.coloradospeed.com/index.php?main_page=product_info&cPath=3654&products_id=10976

It actually wouldn't be hard to back one with just some threaded rod and a nice size washer and bolt even.

Screw that and ls7 crank bolt is like an inch longer and costs 7 bucks

add 1 more degree of timing lol youll break 400rwhp :-) but the pulley will free up some power while improving throttle response

It will add a few hp. Will you notice it? No. Its not possible to feel a 5-10 hp gain on an engine that is putting down 400 to the wheels :lol: Dyno numbers dont mean anything. If you really want to hit 400 try another dyno I guess.

It will add a few hp. Will you notice it? No. Its not possible to feel a 5-10 hp gain on an engine that is putting down 400 to the wheels :lol: Dyno numbers dont mean anything. If you really want to hit 400 try another dyno I guess.

But you probably WILL notice that it revs more freely. It will feel faster than 5rwhp.

Take 4.10 gears for example, you'll lose power on the dyno but the car will feel much faster.

I know that's not the same concept but just trying to illustrate that rwhp numbers aren't everything.

IMO, if you plan on spinning your motor past 6300rpm on a regular basis with the stock alternator then a 25% UD crank pulley is a good idea since it'll keep the the Alt. under 18k even if you spin your motor up to 7k. Or you can install a 3" UD alt pulley to keep the alt. under 18k. If you spin your motor up to 7k with the stock crank pulley and alt/alt pulley you'll already at 18k by 6300 engine rpm, and at 7k your stock alt is spinning at 24500rpm which isn't a good thing for a alt that should never see 18k.
BTW, I figured this with a 98-02 F-body LS1 7.5" crank pulley and stock alt with stock 2.625" alt pulley.

for someone like me, who made 393rwhp it was definately appealing. just enough to bump 4. its a 3 jaw an a few turns away from coming off of there. prob take less than an hour to do. powerbond and asp make some, i have the ATI of course...lol.

IMO, if you plan on spinning your motor past 6300rpm on a regular basis with the stock alternator then a 25% UD crank pulley is a good idea since it'll keep the the Alt. under 18k even if you spin your motor up to 7k. Or you can install a 3" UD alt pulley to keep the alt. under 18k. If you spin your motor up to 7k with the stock crank pulley and alt/alt pulley you'll already at 18k by 6300 engine rpm, and at 7k your stock alt is spinning at 24500rpm which isn't a good thing for a alt that should never see 18k.
BTW, I figured this with a 98-02 F-body LS1 7.5" crank pulley and stock alt with stock 2.625" alt pulley.

and you lost me, so if you spin over 6300 rpms you need or dont need the alt pulley also?

and you lost me, so if you spin over 6300 rpms you need or dont need the alt pulley also?

If you spin over 6300rpm(engine) then I would use the 25% UD crank pulley or a UD alternator pulley, not both. I don't know where you'd get a 3" alternator pulley but it would slow down the alternator the same amount. Either way I'd also bump up the idle speed to maintain the alternators stock rpm at idle to prevent any future battery charge issues.

Ooo ok, so grab a UDP no alternator pulley and be good. Got it but will that over spin the alternator as you stated?

Ooo ok, so grab a UDP no alternator pulley and be good. Got it but will that over spin the alternator as you stated?

25% UD crank pulley, and bump idle up = Good to Go!

Yes thats funny your idle drops when you change over to a 25% UDP i always notice that.

No, your engine idle rpms don't drop, but the speed of all the accessories do, so that's why you'd want to bump up the engine idle speed so the alternator will maintain it's minimum idle rpms and still work correctly.

Cool thanks for the clarification

if you want to break 400 do the UDP ,or consider a electric water pump.or index the spark plugs,or use all synthetic fliuds.

No, your engine idle rpms don't drop, but the speed of all the accessories do, so that's why you'd want to bump up the engine idle speed so the alternator will maintain it's minimum idle rpms and still work correctly.

YES, THIS IS WHAT I WAS TRYING TO SAY. thanks.

if you want to break 400 do the UDP ,or consider a electric water pump.or index the spark plugs,or use all synthetic fliuds.

what? Like regapping or plugs or using a synthetic oil will help hp??? Or are you being a smartass cause its a hp?

dyno your car at the same place on a colder day. If you're looking for a graph that shows over 400, do that. temperature of the day wouldn't matter at all, dyno shops use SAE correction factors to make sure variances in power are minimal if not zero. Unless its a pride thing where you just want to say 400 horses then you can look at the uncorrected power readings.

To me mods that you can actually feel a difference (Long tubes, cam, ls6 int, ect) are worth it. Stuff like ported tb's, pulleys, e. water pump are nice to have but id rather save the money and spend it on something better. On my previous cars I did all the little mods and had regrets later on when I felt no difference.

I just installed my underdrive pulley and I love it, you can definitely tell the car revs up quicker just driving, WOT throttle felt the same as before of course though

all the little things do add up. my only side effect was a slight shudder feedback to the steering wheel when turning it when the vehicle was completely stopped - something you would basically never do. it's a good mod

800 rpm idle got mine good to go with everthing on
lights,a\c,wipers,rear defrost, etc.

I believe it is a matter of taking off a belt, one bolt and possibly using a puller. You could do that while the kids are rotating for bath time.

Had mine for years and after install definately noticed a sotp difference on the Hwy pulls.

I believe it is a matter of taking off a belt, one bolt and possibly using a puller. You could do that while the kids are rotating for bath time.

It never goes that smooth does it?