Underdrive Q

BowTie Eater 5 Liter · 12-04-2004, 07:28 AM

Hey, Quick Q. this motor i have has underdrives, but no alt. Will there be a problem running the underdrives on everything but the alt?

One last thing, this truck is going to be used as a rock crawler, should i go with an electric fan? or will the stock fan with underdrives have sufficent cooling power?

Thanks

GhettoPop · 12-04-2004, 09:55 AM

should be fine. an underdrive pulley on the alt. or the water pump will make that accessory turn less, thus freeing up more power. the original pulley on the alt should be a larger diameter than an underdrive alt pulley, thus the alt will turn faster. i would take a faster turning = better changing alt vs. a 1 horsepower gain with an underdrive alt pulley cuz thats about the only increase u'd see.

the stock fan should be fine. i would use that along with a good water temp gauge. if it runs hot there are many solutions.

KiltedBanshees93GT · 12-04-2004, 09:59 AM

#1: You should be fine, lots of folks do "partial underdrive" you just wont free up quite as much hp (nominal difference)

#2: Honestly, I dont know much about what crawlers need to be able to do. If I was in doubt, I would err on the side of caution. Too much cooling?Good. Not enough? Bad.

J

BowTie Eater 5 Liter · 12-05-2004, 09:45 PM

well basically it will be at an idle almost for a long period of time, just dont want to boil over crawling up a trail. might as well install the electric fan just to be safe.

i didnt choose to put these on the truck for more power, but they came on the motor.

GhettoPop · 12-06-2004, 12:26 AM

why not leave the stock belt driven fan on and install a pusher electric fan in front of the radiator? run the electric fan off a thermostat or put your own toggle switch for total control, or both!

BowTie Eater 5 Liter · 12-06-2004, 11:14 PM

actually, that is a good idea. i may just have to do this. ive got a tarus fan, but its a puller fan, so i dont think i can reverse the current flow and run it as a pusher, or can i?

red82gt · 12-07-2004, 02:00 AM

Just use the taurus fan. It'll cool just as well as the stocker. Another issue is can you get a shroud to fit a stock type fan on a 302 in a bronco II? I'd just do the electric.

12-04-2004, 09:59 AM	#3
KiltedBanshees93GT Registered Member Join Date: Jun 2000 Location: Pigeon Forge Tn Posts: 611	Re: Underdrive Q #1: You should be fine, lots of folks do "partial underdrive" you just wont free up quite as much hp (nominal difference) #2: Honestly, I dont know much about what crawlers need to be able to do. If I was in doubt, I would err on the side of caution. Too much cooling?Good. Not enough? Bad. J __________________ ____________ '66 Mustang Coupe- AKA "Lenore" on disability for a (long) bit '93 GT Mostly stock AKA "Fawkes" Rice Haters Club Member #239 "I find your lack of faith...disturbing." "Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin to slit throats." H. L. Mencken

12-05-2004, 09:45 PM	#4
BowTie Eater 5 Liter Registered Member Join Date: Nov 2000 Location: Maple Ridge B.C. Canada, The Best Place In The World Posts: 871	Re: Underdrive Q well basically it will be at an idle almost for a long period of time, just dont want to boil over crawling up a trail. might as well install the electric fan just to be safe. i didnt choose to put these on the truck for more power, but they came on the motor. __________________ 1984 Bronco II, 36" Michelin Military Tires, 95 EFI 5.0, NP435 Tranny, NP208 Doubler, NP205 Transfer Case, Fill Size Solid Dana 44 Front End, WH Progressive Rate Rock Crawling Coils, Bronco 8.8 Rear, Skyjacker Softride Leafs, 5.13 Gears, Detroit Locker. Final Crawl Ratio Of 175:1 88 GT Best 60ft. 2.181 Best ET 14.350 Best MPH 98.01 ~WRECKED!!!!~

12-06-2004, 12:26 AM	#5
GhettoPop Gimme a Drink! Join Date: Dec 2002 Location: NYC Posts: 694	Re: Underdrive Q why not leave the stock belt driven fan on and install a pusher electric fan in front of the radiator? run the electric fan off a thermostat or put your own toggle switch for total control, or both! __________________ 1990 GT,stock T-5,K&N w/o air silencer,March underdrives,FMS wires,timing@14*,PA Perf 130amp alt,Steeda Tri-Ax Shifter,Steeda adj quadrant/clutch cable/firewall adj,Centerforce II clutch,o/r x-pipe,Magnaflow SS catback,g-load brace, subframes,Bilstein struts/shocks,Autometer gauges, 136k and running strong!

12-06-2004, 11:14 PM	#6
BowTie Eater 5 Liter Registered Member Join Date: Nov 2000 Location: Maple Ridge B.C. Canada, The Best Place In The World Posts: 871	Re: Underdrive Q actually, that is a good idea. i may just have to do this. ive got a tarus fan, but its a puller fan, so i dont think i can reverse the current flow and run it as a pusher, or can i? __________________ 1984 Bronco II, 36" Michelin Military Tires, 95 EFI 5.0, NP435 Tranny, NP208 Doubler, NP205 Transfer Case, Fill Size Solid Dana 44 Front End, WH Progressive Rate Rock Crawling Coils, Bronco 8.8 Rear, Skyjacker Softride Leafs, 5.13 Gears, Detroit Locker. Final Crawl Ratio Of 175:1 88 GT Best 60ft. 2.181 Best ET 14.350 Best MPH 98.01 ~WRECKED!!!!~

12-07-2004, 02:00 AM	#7
red82gt Sober voice of Reason Join Date: Nov 1998 Location: Kelowna, B.C., Canada Posts: 1,514	Re: Underdrive Q Just use the taurus fan. It'll cool just as well as the stocker. Another issue is can you get a shroud to fit a stock type fan on a 302 in a bronco II? I'd just do the electric. __________________ 393W: AFR 205's, hydraulic roller, TKO600.

12-04-2004, 07:28 AM	#1
BowTie Eater 5 Liter Registered Member Join Date: Nov 2000 Location: Maple Ridge B.C. Canada, The Best Place In The World Posts: 871	Underdrive Q Hey, Quick Q. this motor i have has underdrives, but no alt. Will there be a problem running the underdrives on everything but the alt? One last thing, this truck is going to be used as a rock crawler, should i go with an electric fan? or will the stock fan with underdrives have sufficent cooling power? Thanks __________________ 1984 Bronco II, 36" Michelin Military Tires, 95 EFI 5.0, NP435 Tranny, NP208 Doubler, NP205 Transfer Case, Fill Size Solid Dana 44 Front End, WH Progressive Rate Rock Crawling Coils, Bronco 8.8 Rear, Skyjacker Softride Leafs, 5.13 Gears, Detroit Locker. Final Crawl Ratio Of 175:1 88 GT Best 60ft. 2.181 Best ET 14.350 Best MPH 98.01 ~WRECKED!!!!~

12-04-2004, 09:55 AM	#2
GhettoPop Gimme a Drink! Join Date: Dec 2002 Location: NYC Posts: 694	Re: Underdrive Q should be fine. an underdrive pulley on the alt. or the water pump will make that accessory turn less, thus freeing up more power. the original pulley on the alt should be a larger diameter than an underdrive alt pulley, thus the alt will turn faster. i would take a faster turning = better changing alt vs. a 1 horsepower gain with an underdrive alt pulley cuz thats about the only increase u'd see. the stock fan should be fine. i would use that along with a good water temp gauge. if it runs hot there are many solutions. __________________ 1990 GT,stock T-5,K&N w/o air silencer,March underdrives,FMS wires,timing@14*,PA Perf 130amp alt,Steeda Tri-Ax Shifter,Steeda adj quadrant/clutch cable/firewall adj,Centerforce II clutch,o/r x-pipe,Magnaflow SS catback,g-load brace, subframes,Bilstein struts/shocks,Autometer gauges, 136k and running strong!

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