Engine 1994 GT under drive pulley
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Don't bother, almost no gain, possibility of overheating at idle and not enough volts to keep the battery charged and run the accessories at idle.
Isn't that if I use all 3 pulleys ?
I'm talking about just using the crank pulley to avoid all that crap
jozsefsz
15 Year Member
It depends on the size difference of your specific pulley and if it will fit properly without the associate accessory pulleys.
If it fits you could run it, though again depending on the pulley sizes of the matched set it may even be counter-productive.
Agree with @General karthief it's a really bad way to get very minimal, statistically unnoticeable power gain - taxing your charging and cooling systems.
If it fits you could run it, though again depending on the pulley sizes of the matched set it may even be counter-productive.
Agree with @General karthief it's a really bad way to get very minimal, statistically unnoticeable power gain - taxing your charging and cooling systems.
Yes, you can do that. Youll need to wrap string around your pulleys and measure for a belt.
I can't think of any advantage to the under drive crank pully. What reason do you think you need one?
Boostedpimp
Dirt-Old 20+Year Member
You won't get much love for pulleys here... They tend to expose peoples weak 65amp alternators or crappy mechanical cooling fans and sludged up twenty plus year old radiators.
To safely run an underdrive pulley kit you'll need the following:
Electric cooling fan of choice
Alternator upgrade (90amp or 130amp 3g)
Associated power wire/fuse upgrade for the 3g
1 7/8" over drive pulley for the alternator
Most likely a difference size serpentine belt
I've ran them on many foxbodies through the years and with those mentioned changes never had a problem.
Don't think I need one at all. All 3 gave my Fox 8rwhp but had the normal issues with alt & cooling. I have just a March underdrive crank from a friend who went supercharged. Thought id use it in my 94... Figured id ask for experience doing this.
jozsefsz
15 Year Member
Not exactly. It's because it's a huge waste of money and truly ineffective. The equivalent of blood-letting for weight-loss, if you shed a gallon of blood you'll lose 8lbs. but you'll be in pretty bad shape. You're hampering your cooling and charging systems (a higher amp alternator - 94-95's already have 130A alternators - will not deliver more charge while rotating more slowly FYI, and an electric fan - which 94-95's already have - doesn't fix the slower rotation of the water pump unless you want to add an electric one too - further taxing your now hobbled charging system). A ton of expense and wasted effort for that 1/3 of a HP don't you think? You'd make double the gains by slapping a K&N filter in the stock housing and skipping the Big Mac on the way to the track.
I run an underdrive crank and water pump pulley and overdrive alt pulley. The OD alt pulley takes care of my charging issues and my brass 3-core radiator takes care of my cooling. I have had them for 15+ years without issue
This is two examples of well thought out addition of 'speed' parts proving that research and experience does work, if you are going to strap on that under drive crank pulley learn from these examples.
I never had issues with cooling or charging with my sn95. Underdrive everything with a 180* t stat and a 3 core radiator kept everything nice and cool. This was in 95 deg weather.
The 94/95 mustangs have 130 amp alternators too. I doubt you’ll notice much of a difference in charging.
The 94/95 mustangs have 130 amp alternators too. I doubt you’ll notice much of a difference in charging.
Well it was a deffinalty noticable success. Better idle, smother revs... and smoother through the whole RPM range. She seems to take off better to. She now spins the tires more at take off...
And now has a 102.5 belt size. And guess what???
No issues with voltage or cooling at idle...
Win Win... great for a free crank pulley. So there you have it. This is real experience. We will see what the dyno says now... My 88 with the undrives had 7 RWHP on the dyno. We will see. Thanks for the feed back
And now has a 102.5 belt size. And guess what???
No issues with voltage or cooling at idle...
Win Win... great for a free crank pulley. So there you have it. This is real experience. We will see what the dyno says now... My 88 with the undrives had 7 RWHP on the dyno. We will see. Thanks for the feed back
jozsefsz
15 Year Member
Well, congratulations? 
I'm not typically one to hinder someone's joy, but... can't really let this feedback stand for others to come across.
You managed to find a 95 degree day to get stuck in traffic and sit at idle in the middle of summer so you're positive your cooling system wasn't impacted? Dude, it's winter. Even in sunny California you're in the 60's. No one said it would blow up your car, only that it would negatively impact your cooling at peak conditions - when you really need it, which it did if you've now seen 'better performance.'
You also managed to run it at night, stuck in a similar traffic jam, with headlights, radio, and A/C or heater running and didn't see your headlights dim? Seriously, I've had the belt completely off to move the car around in the shop and couldn't brag about such gains. Perhaps those pulleys were made of forged magical fairy dust too? Again, it wasn't going to destroy your alternator, just cut down its peak performance - when you really need it.
You gotta love how these snake-oil mods are always 'proven' by the butt dyno. Smoother, better burnouts, feels stronger my girlfriend swears it does. And unless you do a dyno pull, and immediately swap out the pulleys, and then another run with no other changes, your results (current and previous) are unscientific at best. You do realize a 60 degree day vs a 90 degree day at the dyno is worth over 20hp right? My turbo 5.0 is noticeably more powerful on cool days - so much so that I had to upgrade the ignition system against spark blowout. And even the slightest calibration difference between dynos or days at the dyno is more than that?
On a good day, on an SN95 5.0, which doesn't rev all that high unlike the 4-7hp numbers you've seen posted about Coyotes that go to 7k+, you got 4hp. That's with all the pulleys swapped not just the one. Nothing you can truly feel, it's 100x more likely that it was a nice day outside. I've had my SN95 for almost 25 years, so I've tried pretty much everything. The underdrive pulleys did almost nothing, but made me overheat in traffic. Those cat-backs made the car sound nice, but it still did nothing. And when I finally realized I'd wasted a lot of $ and my car was still whipped by the Camaros and New Edge Mustangs at the time, I decided it was Forced Induction, a stroker kit, or a nice HCI that would solve that problem.
Again, congratulations, if it makes you happy more power to you - at least it was free. But posting for others who come across this, underdrive pulleys are still snake-oil. They have some slight merit, but they do compromise your accessories when you need them, and there are loads of better ways to make much more power. Your exaggerated claims about their effect kind of prove the earlier point - it's wishful thinking. Your car is no more powerful, and your schlong didn't grow an extra 3" either. Snake oil salesman stay in business and have repeat customers because of the placebo effect, and cognitive dissonance - it MUST be faster because I put this time / $ into it.
Finally, congratulations. But the next person who asks, they'll get the same answer around here.
I'm not typically one to hinder someone's joy, but... can't really let this feedback stand for others to come across.You managed to find a 95 degree day to get stuck in traffic and sit at idle in the middle of summer so you're positive your cooling system wasn't impacted? Dude, it's winter. Even in sunny California you're in the 60's. No one said it would blow up your car, only that it would negatively impact your cooling at peak conditions - when you really need it, which it did if you've now seen 'better performance.'
You also managed to run it at night, stuck in a similar traffic jam, with headlights, radio, and A/C or heater running and didn't see your headlights dim? Seriously, I've had the belt completely off to move the car around in the shop and couldn't brag about such gains. Perhaps those pulleys were made of forged magical fairy dust too? Again, it wasn't going to destroy your alternator, just cut down its peak performance - when you really need it.
You gotta love how these snake-oil mods are always 'proven' by the butt dyno. Smoother, better burnouts, feels stronger my girlfriend swears it does. And unless you do a dyno pull, and immediately swap out the pulleys, and then another run with no other changes, your results (current and previous) are unscientific at best. You do realize a 60 degree day vs a 90 degree day at the dyno is worth over 20hp right? My turbo 5.0 is noticeably more powerful on cool days - so much so that I had to upgrade the ignition system against spark blowout. And even the slightest calibration difference between dynos or days at the dyno is more than that?
On a good day, on an SN95 5.0, which doesn't rev all that high unlike the 4-7hp numbers you've seen posted about Coyotes that go to 7k+, you got 4hp. That's with all the pulleys swapped not just the one. Nothing you can truly feel, it's 100x more likely that it was a nice day outside. I've had my SN95 for almost 25 years, so I've tried pretty much everything. The underdrive pulleys did almost nothing, but made me overheat in traffic. Those cat-backs made the car sound nice, but it still did nothing. And when I finally realized I'd wasted a lot of $ and my car was still whipped by the Camaros and New Edge Mustangs at the time, I decided it was Forced Induction, a stroker kit, or a nice HCI that would solve that problem.
Again, congratulations, if it makes you happy more power to you - at least it was free. But posting for others who come across this, underdrive pulleys are still snake-oil. They have some slight merit, but they do compromise your accessories when you need them, and there are loads of better ways to make much more power. Your exaggerated claims about their effect kind of prove the earlier point - it's wishful thinking. Your car is no more powerful, and your schlong didn't grow an extra 3" either. Snake oil salesman stay in business and have repeat customers because of the placebo effect, and cognitive dissonance - it MUST be faster because I put this time / $ into it.
Finally, congratulations. But the next person who asks, they'll get the same answer around here.
Boostedpimp
Dirt-Old 20+Year Member
Well, congratulations?
I don't know you or your car but you sound salty AF right now lol.... If I had to guess at your situation and real world evaluation of any and all underdrive pulley sets. I would assume you spent good money on a pulley set from Ebay, Once that pulley set arrived from China and you paid someone to install them the gobs of earth shattering horsepower and torque you built up in your mind to be the pay off never showed up on the butt dyno. Am I close?
Like I said before, some make it work, some not. The under drive pulley idea was a race car thing that found its way to the street, road racers mostly but it worked on drag cars too where they don't idle much and don't sit in traffic. As for the hp claim the 2 or 5 hp gain has been proven on the dyno, but the results on the street are not even noticeable, all you have to do to skew the butt dyno results is bump the timing up a few degrees and stick some high octane fuel in the tank. It's just like the short vs long tube header thing, I like long tube headers and I think it helps low end torque, but with the mods my car has I doubt I would notice much if any difference with short tubes.
Joz may be grumpy but it is his opinion/experience with pulleys.
Now you you can stack up the 5 hp here and 5 hp there with little mods like I have done and it does add up, the goal is part of a plan. If the plan is a dependable street car I would not do the under drive pulleys.
Joz may be grumpy but it is his opinion/experience with pulleys.
Now you you can stack up the 5 hp here and 5 hp there with little mods like I have done and it does add up, the goal is part of a plan. If the plan is a dependable street car I would not do the under drive pulleys.
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