I have a '76 460 in my truck & am wondering are there factory pulleys I can put on my truck that will underdrive? Example would the crank pulley from a 302 mount to my crank & be smaller in D giving me an underdrive situation? I am looking to pick up whatever hp I can with minimal investment. I can buy a billet set for just over $200 but was hoping I could swap in something factory.
Underdrive pulleys
1 - 20 of 25 Posts
other Ford 4 bolt will interchange , spacing might need to be done , crank or driven units for belt aligment
forgot , doubt you see a noticeable power gain , with a stock engine
Joined
·
10,346 Posts
Yes, 20hp at rpms you'll never want to see, and only at those rpms. Be aware it can help a tad, but then you also are asking for potential secondary problems, like alternator undercharging, cooling issues, harder steering at low speed from a slow PS pump, etc. It's generally not considered a good trade-off for a driver.Thanks. It's not a stock 460The advertisement for the billet pulleys says you can pick up 20 hp.
David
All problems I had with my underdrive pulleys. Well, no power steering, but definite charging and cooling problems. You could just get a smaller crank pulley and only cost about $75 or less.
klutz , do tell how much power will be gained .
The water pump I planned on running the Edelbrock alum version that is supposed to put out something like 20% higher volume. My thoughts were to also use an elec. motor to run it. Clutch fan is going by the wayside in favor of an elec. out of a Lincoln Mark VIII. My only potential issues should be PS & charging but I plan on swapping to the 3G alternator which should help a bit. I was just thinking every little bit would help.
As mentioned previously, what you are planning to do will only result in power savings @ high RPM's. What is the stop light to stop light speed limit in your area?
If you just use a WOT cut-out switch for the ALT (and AC if so equipped) it will save you a lot of money and effort (IMO).
Most likely the biggest drag will be the mechanical fuel pump (after the WP). And an electric driven WP for the street?
Joined
·
3,658 Posts
And everyone knows Honest Tom would never lie, that's why they call him honest!Thanks. It's not a stock 460
Joined
·
3,658 Posts
Average alternator efficiency is 50-60%.
An 80A alternator at 14.5 volts generates 1160 watts. At 55% efficiency, it takes 2100 watts to turn producing full power. One horsepower is "half a Columbus" of watts (1492/2=746 Watts/hp)
So, at max output, an 80A alternator draws 2100 Watts x (1hp/746 Watts) = 3hp
If you underdrive your pulley 2:1 instead of 4:1, you also require 2x the engine RPM to generate any power at all.
If you stop reading right here it means all you'll gain from disconnecting the alternator completely is 3hp, and that's only if you're using 100% capacity, and you may compromise idle charging.
For more theory that's really not that important, it will draw 3hp ALWAYS at full load regardless of engine speed, as long as you are above the minimum and ramp up speed:
![]()
Here's an example graph of alternator RPM vs output. When the engine is off, field current is maxed out, trying to "spark" the alternator into producing more current, but zero hp input means zero watts output. As the alternator starts rotating, it starts generating power, while the field current stays maxed. Eventually, the speed is high enough that the alternator is producing maximum output, and any increase in speed means the regulator will decrease the field current to maintain proper voltage - otherwise you would overcharge your battery. Since the field current is decreasing as RPM increases, power generation remains constant, which means power drawn from the engine is constant.
So, the max you gain is 3hp, and ONLY if you need maximum alternator output to maintain battery voltage; the effect of underdriving your alternator by 2 versus 4 means you won't reach max power output of your alternator until the engine is at twice the RPM. But are you using full output of your alt? Most likely, no.
What happens to idle power generation? Suddenly it takes twice the RPM to generate any power at all and you no longer charge the battery at idle - when you're in the pits, stuck in traffic at night in the rain with the wipers and defroster going, when you actually need the pulley speed.
So what about your water pump? How much power does it take? I haven't done a back to back comparison because I don't need an electric pump for the street, but a little online research tells me 2-4hp. But how long will you make that extra 3hp without any coolant left in the radiator? If you DO underdrive the waterpump, don't get a higher flow water pump - they actually flow worse near idle because the impeller is designed for high flow at higher RPM.
Also, if you drive the pump with a motor... where does that electrical power come from? Power usage reduction of an electric pump comes from it spinning a constant speed, because drag passes are short and you sit in the pits for a long time. The cooling system absorbs that heat and rejects it on the idle home. On the highway, where load is constant, suddenly you might find the electric pump can't keep up at 100% duty cycle.
Power steering? Well, who needs power steering anyways?
An 80A alternator at 14.5 volts generates 1160 watts. At 55% efficiency, it takes 2100 watts to turn producing full power. One horsepower is "half a Columbus" of watts (1492/2=746 Watts/hp)
So, at max output, an 80A alternator draws 2100 Watts x (1hp/746 Watts) = 3hp
If you underdrive your pulley 2:1 instead of 4:1, you also require 2x the engine RPM to generate any power at all.
If you stop reading right here it means all you'll gain from disconnecting the alternator completely is 3hp, and that's only if you're using 100% capacity, and you may compromise idle charging.
For more theory that's really not that important, it will draw 3hp ALWAYS at full load regardless of engine speed, as long as you are above the minimum and ramp up speed:
Here's an example graph of alternator RPM vs output. When the engine is off, field current is maxed out, trying to "spark" the alternator into producing more current, but zero hp input means zero watts output. As the alternator starts rotating, it starts generating power, while the field current stays maxed. Eventually, the speed is high enough that the alternator is producing maximum output, and any increase in speed means the regulator will decrease the field current to maintain proper voltage - otherwise you would overcharge your battery. Since the field current is decreasing as RPM increases, power generation remains constant, which means power drawn from the engine is constant.
So, the max you gain is 3hp, and ONLY if you need maximum alternator output to maintain battery voltage; the effect of underdriving your alternator by 2 versus 4 means you won't reach max power output of your alternator until the engine is at twice the RPM. But are you using full output of your alt? Most likely, no.
What happens to idle power generation? Suddenly it takes twice the RPM to generate any power at all and you no longer charge the battery at idle - when you're in the pits, stuck in traffic at night in the rain with the wipers and defroster going, when you actually need the pulley speed.
So what about your water pump? How much power does it take? I haven't done a back to back comparison because I don't need an electric pump for the street, but a little online research tells me 2-4hp. But how long will you make that extra 3hp without any coolant left in the radiator? If you DO underdrive the waterpump, don't get a higher flow water pump - they actually flow worse near idle because the impeller is designed for high flow at higher RPM.
Also, if you drive the pump with a motor... where does that electrical power come from? Power usage reduction of an electric pump comes from it spinning a constant speed, because drag passes are short and you sit in the pits for a long time. The cooling system absorbs that heat and rejects it on the idle home. On the highway, where load is constant, suddenly you might find the electric pump can't keep up at 100% duty cycle.
Power steering? Well, who needs power steering anyways?
how much money will be saved klutz ?
most like saving money , so how much coin will be saved ?
BTW , you know what the a/c does on oem cars/trucks at w.o.t ?
That's why I am running it by folks before putting my money on the table. Along with this is I can use factory pulleys of some sort they can be had for far less money.
Providing your name isn't Honest Tom this is good stuff.Average alternator efficiency is 50-60%....Power steering? Well, who needs power steering anyways?
So any thoughts, anybody, on wiring the water pump motor into a temp trigger as fans are kicking the water pump on & off as needed? PS stays. To another question, when I installed AC into cars (back in the 80's) WOT kicked out the clutch diverting full power to the engine. I have no idea how AC behaves nowadays on new systems.
Joined
·
10,346 Posts
Electric pumps must always run and flow must always be in the system. In other words, you can't shut the water pump off when the engine is running for several reasons. Personally, for the labor and money involved, I'd use some other ways to reliably add more power. Your ideas are not without merit, but only at higher levels of competition where you're splitting hairs to gain the edge - not where you can add substantial HP for better results for less money or less labor. How about a listing of what you've done to it so far, and what you primarily use it for?
David
what is the specs fort this not stock 460 ?Thanks. It's not a stock 460
what HP does it make ? RPM the max power is at ?
like said if your engine doesnt fall into the range of such mods . ...no gain will be noticed
Right now it is only 375-400 hp but it comes out this winter for a complete build with sights on 650 hp. Right now the ceiling is still at 5500 rpm.
Joined
·
3,658 Posts
Hah, not until I start selling this stuff. I'm wrong often enough I wouldn't take any money for the helpProviding your name isn't Honest Tom this is good stuff.
But that's a big no no. Without water flow you will have localized hot spots that can boil your coolant all while your temp gauge reads normal. When a fan's off you still have airflow when the car is moving, and a considerable amount of heat that just radiates without airflow as long as water is circulating. Without a water pump you're relying on thermo-siphon. Which doesn't work past about 40hp.
The lack of system pressure from the pump also lowers your boiling point a little bit, making steam pockets even more possible.
However, there are PWM based systems that can adjust the speed of an electric water pump. But like I said, that's maybe a 10 amp difference, which is less than half a horsepower.
650 hp at 5500 rpm ! worry of the cost of pulleys !
by chance they are worth 20 hp . be the cheapest 20 hp
1 - 20 of 25 Posts
Join the discussion
