[Super Chevy]

i bought a Hays aluminum flywheel at a swap meet. im having it balanced to match my old flex plate right now. i was just wondering what kind of gains i should expect. would it increase wheel horsepower or will it just allow my engine to spin up faster or maybe both?

thanks

[DoubleVision]

lighter flywheels tend to help in cases of where high RPM is needed and lightness is a factor, I doubt they`ll be any horsepower gains, but there will be a difference in the engines personality, heavy flywheels are used in drag race cases, since a hole shot is always important, the heavy flywheel stores massive amounts of energy, which results in explosive out of the hole power. a light flywheel is needed in circle track racing, since off the corners where the engine is needed to rev and rev quickly a lighter mass is needed and high RPM operation is sustained.

[lluciano77]

I have tried to explain the heavier flywheel theory to someone before, and he just would not except that the engine would stall up faster. Some people just don't want to learn I guess.

[NorthStar]

It will rev like a chain saw but it will also lose rpm faster than a heavier flywheel would.
Is your car fuel injected? The only reason I ask is that it will lose rpm so fast sometimes you get an idle that will kind of hunt for few seconds till the computer catches up when decellerating fast.

I have an aluminum flywheel(driveshaft too) on my car and really like it.

[Super Chevy]

no, it is carbureted. i forgot to mention that i have converted to a 4-speed manual (hence the old flexplate is needed for balancing). since my peak horsepower and torque are at a higher rpms between the 4000- 5000 area (according to decktop dyno) wouldn't this benifit me to get to those rpms faster?

[Rubberman2003]

What you need is a John Deer B flywheel, they are only roughly 300lbs (cause the motor would stall if the flywheel wasnt that heavy to have enough enertia to carry the motor around to the next cycle. If you all remember those tractors.....2cylinders

Really though, the info posted sounds correct to me.

[Super Chevy]

ok, so anybody else who could answer my question, im not saying any of ur info is wrong. i just stated some more info about my application. id under stand if my hp and torque was lower in the rpm to keep the enery stored up as long as possible but peak hp is at 5000rpm, i am not going to be reving ths thing to 5000 rpm, with a heavy flywheel, store up the energy and then dump the clutch and hope it even hooks up, (the tranny would explode!!), wouldn't it get me to my needed power and torque faster? the engines rpm limit is 5500 rpm, so i wouldn't even be able to stay in those upper rpms for very long.

[deuce_454]

it doesnt make any difference for static rpm horse power, BUT the lower the rotating mass the less will have to be acceterated by your engine and the more can be used accelerating your car. its called the polar moment of inertia, it is a theoretical size that combines the mass of your object (ie your flywheel) and the distance of that mass from the axis arround which it revolves. But when you calculate it you multiply it by the square of the gearing ratio by which it is attached to your car. So reducing the mass of your flywheel will have a big effect on acceleration. but also make for a more erratic idle (youd propably have to increase your idle rpm to get it to run smooth, and it will be easier to stall your car)

to put it in real world language. The heavier your rotating assembly is, the more power will be used getting it up to speed, and your low gear acceleration will consequently suffer. (especially with tall rear end gears) which is often why people bennefit from mounting small diameter converters.

try as an experiment to tahe a 6 foot pole (a driveshaft will do just fine) and try and spin it arroynd its longitudinal axis, and youll fint that it is very easy to get it up to 3-4 revolutions per second. and stop it again. now maintaing the weight (using the same driveshaft) hold it over your head and do the same arround a transverse axis (spinning it like a helicopter rotor) and you will find that it requires considerable energy and time to get it up to even 1-2 revs per second amd stopping it again will snap your wrist if you simply held on tightly.

all that energy can be used to launch the car, but once the clutch is engaged, then its only dead weight.

[BOBCRMAN@aol.com]

Duece_454 is correct. Now in your case. If you have a car with street tires and a decent rear (3.25-3.90 etc) the light wheel will keep you from burning up the tires on a drag strip start, the engine doing most of the pulling. The same situation with a heavy wheel would light up the tires. A buddy of mine put an aluminum wheel in his 66 Chevelle 396 back in the late sixties and he could launch the car on 7" slicks, but his times suffered because of the lack of initial forward movement that was gained with a 30lb. wheel and 10" slicks. If you are not concerned with off the line acceleration or don't have a big tire go for the light wheel.

[Super Chevy]

thanks for all of the help and the info, my car has a 3.36 rear gear so it should make a pretty interesting expierence. and the first gear in my tranny is 3.11 to 1. im always just gonna be running street tires. mostly the car is gonna be daily driven but be having some fun with it also. im also gonna go to the drag strip just to see what it is gonna do. thanks again for the help and for telling my ur expierences with them. what do you think i should set the idle to, 800rpm? higher?

[jimfulco]

With a lighter wheel, you'll have to slip the clutch more when starting off from a dead stop in order to keep the engine from stalling. I had a 16# iron flywheel in my '69 Nova with a puny stock 250cid 6 & Muncie M20 (2.52 low) & 3.08 rear. It was a pain in the butt on an easy drive-off from a stop sign, so I put the stocker back on it. Your gearing & the bigger motor should help you quite a bit though.