When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Im looking at the underdrive pulley being sold at hawks motorsports. "Lt1 march power and amp series underdrive and overdrive pulley set". I found one other thread talking about a similar issue. Its advertised as a 25 percent underdrive so would I need a different size pulley as well ? I think it is a 37 inch pulley, am I understanding that correctly ?
I did both underdrive and overdrive and used what was then called a "590 K6" belt. It was too long with the underdrive pulley and would screech when the A/C was turned on. I'd say call them, but these days anyone you call usually doesn't know any more than what's on the description on the internets. The size I gave is at least a start.
So you did an over drive kit and an underdrive kit ? The kit says it does both but what im thinking is that the main pulley is smaller but makes the alternator pulley bigger, hence over drive underdrive. Just seeing some interchangeable words going on. When looking at the name of the belt how do you go about reading it ? is the 90 the length of the belt or the 59 ?
I have the ASP set. The underdrive is a smaller crank pulley and the alternator pulley is also smaller which overdrives the speed allowing it to charge at a faster rate. Not using the alternator pulley may cause charging issues. I used the shortest belt I could get on which a k060605 which longer than the 590 but different sets require different belts. At least you have a starting point but use the shortest, tightest belt so it doesn't slip.
So you did an over drive kit and an underdrive kit ? The kit says it does both but what im thinking is that the main pulley is smaller but makes the alternator pulley bigger, hence over drive underdrive. Just seeing some interchangeable words going on. When looking at the name of the belt how do you go about reading it ? is the 90 the length of the belt or the 59 ?
The underdrive pulley was done first. That slowed down all accessories including the alternator which then, like many others, experienced a dead battery because the alternator was not spinning fast enough to keep up with charging the battery at low engine speeds. March then developed an "overdrive" pulley, which is physically smaller than the stock one, to speed up the alternator RPM. Paired with the underdrive pulley the alternator spun at a fast enough RPM to keep the battery charged. That belt size will work with an U/D-O/D pullies, but I do think it is too long due to what I said in my previous post.
Honestly I don't know how belts are read these days. I do believe the "590" I referenced is in millimeters and 59 would be in centimeters.
this explains belt #. Belts typically come in 1/2" increment lengths. Just buy the longer or shorter belt you need, likely 1/2" shorter than what you have if going to a smaller pully set
Camed motors often idle higher than stock so a smaller alternator pully is not needed. I have a ATI smaller damper but stock ALT as my idle RPM is 850 with my H/C 383. Been fine for over 20 years
Camed motors often idle higher than stock so a smaller alternator pully is not needed. I have a ATI smaller damper but stock ALT as my idle RPM is 850 with my H/C 383. Been fine for over 20 years
My guess is this is accurate unless daily driven in rush hour traffic, which is where a lot of cars had an issue. Especially in southern states in the summer where the A/C and Blaupunkt were at 11. Especially auto cars, but most likely a moot point in this day and age since not a lot of these things are on the road on the daily anymore.
I got the pulley in and it is great. Looks good and I get get to the sensors alot easier. Shiny and Chrome. Too hot today so ill do the overdrive pulley for the alternator tomorrow. I have a torqhead 24x kit and it clears the hub perfectly and doesnt get in the way to cause sensing or reading issues. I did realize the 3 holes arent in a perfect triangle and there is a specific way you have to align the pulley. Also I did need a new belt. 6 rib, 59.45 inch. Part number : 5060595.
I got the pulley in and it is great. Looks good and I get get to the sensors alot easier. Shiny and Chrome. Too hot today so ill do the overdrive pulley for the alternator tomorrow. I have a torqhead 24x kit and it clears the hub perfectly and doesnt get in the way to cause sensing or reading issues. I did realize the 3 holes arent in a perfect triangle and there is a specific way you have to align the pulley. Also I did need a new belt. 6 rib, 59.45 inch. Part number : 5060595.
You do know you are also supposed to bolt on the stock damper as well, right?
Without the stock damper also being bolted back on, you can experience what I did too many years ago as a kid. The timing gear bolts in the cam all sheered off and sent timing gear teeth and shrapnel through the engine.
Doh!
I never knew it would be that important damn ! Thanks for letting me know. I got it put on and it was aligned with all the bolts first try. Got the Alternator overdrive on as well. Definitely will say the engine is idling smoother and is more responsive. who knows how much im really getting from it. But its cool C:
I got the pulley in and it is great. Looks good and I get get to the sensors alot easier. Shiny and Chrome. Too hot today so ill do the overdrive pulley for the alternator tomorrow. I have a torqhead 24x kit and it clears the hub perfectly and doesnt get in the way to cause sensing or reading issues. I did realize the 3 holes arent in a perfect triangle and there is a specific way you have to align the pulley. Also I did need a new belt. 6 rib, 59.45 inch. Part number : 5060595.
Where exactly does your tensioner sit? I ended up using a shorter belt with that underdrive pulley on my own car.
Ill get a pic of the position of the tensioner tomorrow ! I wonder why or how an ac delete would have a different pulley. Also I will note after driving the car for a bit I notice that when the high speed fans kick in and im stopped at a light without my head lights on, Ive got to give it some gas to get up to around 900 rpms to get the volts back up. Even with the alternator pulley swapped.
Ill get a pic of the position of the tensioner tomorrow ! I wonder why or how an ac delete would have a different pulley. Also I will note after driving the car for a bit I notice that when the high speed fans kick in and im stopped at a light without my head lights on, Ive got to give it some gas to get up to around 900 rpms to get the volts back up. Even with the alternator pulley swapped.
Underdrive pulley ain't worth it IMO. Replace them there front cover seals, M8!
The underdrive pulley was done first. That slowed down all accessories including the alternator which then, like many others, experienced a dead battery because the alternator was not spinning fast enough to keep up with charging the battery at low engine speeds. March then developed an "overdrive" pulley, which is physically smaller than the stock one, to speed up the alternator RPM. Paired with the underdrive pulley the alternator spun at a fast enough RPM to keep the battery charged. That belt size will work with an U/D-O/D pullies, but I do think it is too long due to what I said in my previous post.
Honestly I don't know how belts are read these days. I do believe the "590" I referenced is in millimeters and 59 would be in centimeters.
590 means either mm or more likely 59.0". A 595 would be 59.5". I want to say if it were mm there'd be 4 digits. I too run an underdrive pulley and the stock belt was too long, I'd lose PS momentarily when I would bump an apex curb. I run a 5 rib belt, I forget the length, but it put my tensioner where it was happy. I want to say it's 59 5/8"?
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Slideshow: The controversial Ferrari F6 swaps its original flat-12 for a Corvette Z06-derived LT4 V8 and sends power to four rear wheels through a custom-built drivetrain.
7 Most Reliable High-Performance Engines GM Has Ever Built
Slideshow:These GM engines didn't just make huge power, they survived abuse, boost, track days, and six-digit mileage with a reputation for refusing to quit.
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.
Underdrive Pulley, Need a different belt ? 
