Obsol3te

Seeing as how Aluminum Underdrive Pulleys free up some horsepower, I was wondering how much the big heavy Flywheel would freeup if I replaced it with an Aluminum?

Say if you were to put it on a stock fox, whats the average HP/Torque itll free up?

Milky

First, the aluminum u/d pulleys just free up drag on the crank, not so much weight though a lighter poulley is nicer. An aluminum flywheel is a flywheel in the sense that it won't free up any actual horsepower. If you replace with aluminum your engine will rev faster and take a off a bit faster. I live with hills around so it was kinda bad going up hill the momentum of the steel flywheel wasn't there...

midnitestang

So it doesnt really effect torque either? I was thinking of doin the same when I replace my clutch. But if it doesnt help that much then Ill just wait till I finish my 351.

Obsol3te

egh...yea damn
i figured it would relieve craploads of weight on the crankshaft...
pretty much act like underdrive pulleys but be like 3 times as effective...

Milky

horsepower comes from torque. It is impossible to get one without the other. Its a tasteful mod if you will be racing drag like, but if its a street car as well its not very important, imo.

roundman

Milky is right on this one. the flywheel serves two functions. first is as an intertial rotating mass that smooths out the engine running since it helps keep the crankshaft spinning between firings of the cylinders. a V-8 only fires every 90 degrees of crankshaft rotation, so in between firings it's just coasting and a heavy flywheel stores up the rotational energy to keep the crank turning until the next cylinder fires. second it provides a means to connect the power of the crankshaft up to a transmission and drive train so the car can move. a lighter weight flywheel is primarily a drag racing modification as it will allow the engine to rev up to it's powerband faster since the rotating mass is lower, but it doesn't add HP or torque, it just lets the engine get up where it makes the best torque and HP a touch faster which is critical in a drag race but not much important on the street. you also have to be careful when swapping flywheels or harmonic balancers to keep the proper crankshaft balance. small block Fords are externally balanced with weights added to the balancer and flywheel to 50 oz-in of imbalance. older small blocks used 28 oz-in, so you can't just mix and match parts or you'll have a mess with a very unbalanced rotating assembly which will quickly beat the manin bearings out of itself.

Obsol3te

so you recommend leaving the steel flywheel?
hrmm
always thought the aluminum freed up a bit of torque/hp(what i've been told by my uncle[mechanic] and my stepdad)

well then I guess an Aluminum Driveshaft wouldnt really be too beneficial either then?

roundman

anything lighter in the drivetrain takes a little less torque to rotate and will allow the engine to get up to the higher rpms faster, but on the street it wouldn't make all that much difference relative to the cost of an aluminum driveshaft. lighter weight wheels and tires do the same thing, it is less rotating mass which can be accelerated up to speed faster than the heavy masses of steel wheels and heavy tires. your uncle and stepdad are right in a way but not for the way you first tried to explain your theory. it doesn't make more torque, it uses up less to rotate and leaves more available to accelerate the vehicle.

Obsol3te

so it DOES free up torque

pretty much like the UNDERDRIVE pulleys
like i said above
right?

vfast

actualy on the street the car willnot rev faster and will tend to bog to a certain point..the heavy stock one builds up energy to hold on longer....the main reason racer use alum is because turn 8k the alum it less likely to come up thur the dash as a heavy one breaking bolts can do..my dad;s left foot will atest to this