I put under drive pullies on my new edge GT. Definitely makes the engine more peppy and rev faster. Well worth it. Add off-road x pipes with flowmasters, cold air intake with 75 mm plenum intake, and 4.10 gears and you have a fun 2003 Mustang GT. People be surprised how quick my “old mustang” is.
@@latemodelrestoration So just out of curiosity, what if you get the underdrive crank pulley, and cobra water pump pulley and cobra alternator pulley? That will be the smallest diameter of all 3.... Just curious
I have underdrive pulleys on my 347 5.0 / Fox-based engine in my Factory Five Cobra and I seem to have trouble with cooling in stop and go traffic. I suspect it's because the water pump is turning a lot slower. The headlights also dim at the stoplight.
Can't thank you guys enough for excellent prices, quality, and customer service. (Big thanks to John)! I have actually received items the next day from you guys! Just wondering if you have any plans to make the Cobra pulleys out of steel, anodized black?
What size belt did you use? I’m thinking about a 93 cobra pulley upgrade, only mod is a deleted smog pump, I wonder if a 84.5” belt will work with cobra pulleys and deleted smog
Hey man I know this is a old comment but I’m interested in running that cobra pulley/smog pump bypass combo as well. Did you ever figure out what size belt it was?
Looks like a stock alternator in the vid. FWIW I ran under drive pulleys for years on my Fox with a 3G alternator and the volt gauge never flinched under load.
@@BlueOvalTavern did you also run electric fans? I'm trying to figure out if I should run underdrives with an electric fan, 3g alternator as well as a couple of subs. Just wondering if I should go with the 130amp or the 200.
@@GreenToFeelBlue I've never used an electric fan. A 130 amp would most likely run just fine even with underdrives, but I would probably get a 200 amp since the price bump isn't much and to make sure it would provide for the subs.
Hi Jesus, With the installation of the underdrive pulleys, we do recommend upgrading the stock alternator, due to the difference in diameter size from stock. You can email or call us using the link below for more assistance: lmr.com/contact
When the pump is spun too fast, cavitation occurs (air bubbles) and flow drops dramatically, you plan to drive it like you mean it then there is no drawbacks, for idling and Sunday drives maybe not the best
haha so you got underdrive pulleys on your sunday drive car? you know why boat engines usually have properels sized and matched to the rpm it turns? because to high rpm on a propeller will only whipp air and ruin water flow, that is what happends with manny wather pumps on cars when they are driven hard. or the servo fluid can actually start overpresuring and that is a problem, under drive pulleys can actually help the cooling on engines. and if you want charge dont swap the dyno pulley or get a smaler one to make up for it.
not sure what you're getting at but i was referring to fox mustangs not boats... ud pulleys come with larger wp, alt pulleys and either a stock size crank or smaller (overdrive) crank pulley. depending in the cam you have, thr condition of your wp and alt, you will have to increase your base idle in order to bring back proper function of your accessories. And that might not help either.
@@angry408w7 jeah but if you understand how a watherpump works you would understand what i was getting at, and if you increse the idle to get the acesories to spin at original speeds you got the wrong mindsett bud. the whole point is to free up power for more active driving, and who drives at idle? once you get going the alternator charge more than it needs and the wather flows so you wont overheat. but if you are a parking loot queen ideling in the loot all day i can see you having issues.
@@Stale_Mahoney no i got the idea behind it. no one drives at idle, but in the normal driving lower rpm with lights on and the ac going, normal everyday driving, you will have problems. at wot or higher rpm power will show on a dyno.
@@angry408w7 well then i aplaud you because you are able to ceep the rpm's at a low i am not able to for daily driving, but again this is not a mod for sunday drivers, this is for those who use the engines.
Great info for sure, fact is pulleys do make power, love the OG fox mods!
OG Fox mods for the win all day!! 🙌
I put under drive pullies on my new edge GT. Definitely makes the engine more peppy and rev faster. Well worth it. Add off-road x pipes with flowmasters, cold air intake with 75 mm plenum intake, and 4.10 gears and you have a fun 2003 Mustang GT. People be surprised how quick my “old mustang” is.
@@latemodelrestoration So just out of curiosity, what if you get the underdrive crank pulley, and cobra water pump pulley and cobra alternator pulley?
That will be the smallest diameter of all 3.... Just curious
Those Cobra pulleys along with a 3g alternator upgrade should do the trick! Thanks to Brew2L and Foxcast for pushing out the additional info !
Yeah that was my question, pulley size difference between 3g alternator upgrade and under drive alternator pulley for the cobra style
Impressive results . That’s actually nice back for the buck.
I have underdrive pulleys on my 347 5.0 / Fox-based engine in my Factory Five Cobra and I seem to have trouble with cooling in stop and go traffic. I suspect it's because the water pump is turning a lot slower. The headlights also dim at the stoplight.
yes, they usually run hot
Any fix besides going back to stock?
Lower temp thermostat
Excellent info! Next could you do a video showing the power gains for a efan on a foxbody!?
and then you need $400 alternator upgrade to pull the extra 30 amps.
itza money snowball
Running LED headlights with underdrive pullies should return it to 12.6v perhaps?
should be around 13.8
Can't thank you guys enough for excellent prices, quality, and customer service. (Big thanks to John)! I have actually received items the next day from you guys!
Just wondering if you have any plans to make the Cobra pulleys out of steel, anodized black?
We appreciate the feedback! Thank you!
Not at this time. Maybe in the future!
I prefer a lightweight stock diameter pulley. Uses the stock belt and don't have to worry about any charging issues.
Where can you find lightweight stock diameter pulleys? I would be interested in those.
What size belt did you use? I’m thinking about a 93 cobra pulley upgrade, only mod is a deleted smog pump, I wonder if a 84.5” belt will work with cobra pulleys and deleted smog
Hey man I know this is a old comment but I’m interested in running that cobra pulley/smog pump bypass combo as well. Did you ever figure out what size belt it was?
Thank you
Very good test.
Great video! This is a age old debate that is now proven for all the haters lol
I may have missed it but was that with a stock or a 3g alternator?
Looks like a stock alternator in the vid. FWIW I ran under drive pulleys for years on my Fox with a 3G alternator and the volt gauge never flinched under load.
@@BlueOvalTavern did you also run electric fans? I'm trying to figure out if I should run underdrives with an electric fan, 3g alternator as well as a couple of subs. Just wondering if I should go with the 130amp or the 200.
@@GreenToFeelBlue I've never used an electric fan. A 130 amp would most likely run just fine even with underdrives, but I would probably get a 200 amp since the price bump isn't much and to make sure it would provide for the subs.
Are there different pulley options for a 351w or would these options swap?
Great video!
will the belt size change when doing the underdrive pulleys i am interested in doing this.
The 1993 Cobra-spec pullies will require a shorter length belt. Standard underdrive pullies for Fox Mustang do not. -Landan
With the sve pulleys the belt is the same?
Not exactly. Here's a guide for more information: lmr.com/products/fox-body-belt-routing-length-50
Was it a stock alternator?
Should these pulleys cause me to lose alternator charging power?
Hi Jesus,
With the installation of the underdrive pulleys, we do recommend upgrading the stock alternator, due to the difference in diameter size from stock. You can email or call us using the link below for more assistance: lmr.com/contact
Nice wheels what are those??
They're our SVE Mesh Wheels. Here's the link: lmr.com/products/mustang-sve-mesh-wheels-79-93
@@latemodelrestoration very nice wheels, I’ve swapped to five lug but thank you!
What happens when underdriving the water pump?
the wather pump works bether at high rpm's then thats what is happening
gets hot on marginal days
When the pump is spun too fast, cavitation occurs (air bubbles) and flow drops dramatically, you plan to drive it like you mean it then there is no drawbacks, for idling and Sunday drives maybe not the best
and then it runs hot
Fit 94-95 cars?
No, 79-93 only
If you were concerned with the voltage you would have changed to a 94+ alternator by now
He could have cooling issues as well now. I say leave the factor pulleys on there.
do you like overheating, undercharging, idle problems? get under drive pulleys.
haha so you got underdrive pulleys on your sunday drive car? you know why boat engines usually have properels sized and matched to the rpm it turns? because to high rpm on a propeller will only whipp air and ruin water flow, that is what happends with manny wather pumps on cars when they are driven hard. or the servo fluid can actually start overpresuring and that is a problem, under drive pulleys can actually help the cooling on engines. and if you want charge dont swap the dyno pulley or get a smaler one to make up for it.
not sure what you're getting at but i was referring to fox mustangs not boats...
ud pulleys come with larger wp, alt pulleys and either a stock size crank or smaller (overdrive) crank pulley. depending in the cam you have, thr condition of your wp and alt, you will have to increase your base idle in order to bring back proper function of your accessories. And that might not help either.
@@angry408w7 jeah but if you understand how a watherpump works you would understand what i was getting at, and if you increse the idle to get the acesories to spin at original speeds you got the wrong mindsett bud. the whole point is to free up power for more active driving, and who drives at idle? once you get going the alternator charge more than it needs and the wather flows so you wont overheat. but if you are a parking loot queen ideling in the loot all day i can see you having issues.
@@Stale_Mahoney no i got the idea behind it. no one drives at idle, but in the normal driving lower rpm with lights on and the ac going, normal everyday driving, you will have problems. at wot or higher rpm power will show on a dyno.
@@angry408w7 well then i aplaud you because you are able to ceep the rpm's at a low i am not able to for daily driving, but again this is not a mod for sunday drivers, this is for those who use the engines.