Flywheel Question, Is lighter better? Options

[ScottD914]

(IMG:style_emoticons/default/idea.gif) Gentlemen and Ladies;
I've spent the winter rebuilding my 1.8 up to 2142 (or there about). The
question I would pose is about the weight of the flywheel I need to purchase.
My new Eagle Rods and KB pistons are much lighter than the stock equipment
from 1974, does the sum of the mass in the case need to correspond with the
mass of the flywheel somehow? I've seen two choices: 17lbs and 12 lbs. Your
thoughts? Thanks. ScottD

[VaccaRabite]

With a lighter flywheel, your engine will spin up faster. The lighter the flywheel, the faster it will gain revs. However, it will also spin down faster when you let off the throttle. As long as you keep your foot on the throttle, , you are going to be golden with a light flywheel.

Getting started in 1st gear can get tricky the lighter a flywheel goes. The less mass in the wheel, the more precise you need to be with your clutch and gas transition. With a full weight flywheel you almost do not need to add gas to get moving, it is very forgiving as the wheel contains a lot of kinetic energy, keeping the motor from stalling. The less mass to the wheel, the less energy it stores, and the less forgiving the transition is. This is the reason you will hear folks say that a light flywheel is "not streetable."

The other thing that a heavy flywheel will do is mask an engine that is a little out of balance - smoothing it out a little. A flywheel is like a gyroscope, and it will smooth out minor balance issues with an engine.

So, thats the theory. Match the weight of your wheel to the type of driving that you want to do. The more stop and start driving, the heavier a wheel you want for comfortable driving.

My 2056 used a 10 or 12 pound wheel for a while, but it needed to be resurfaced and did not have enough meat to be ground again. I went with stock weight for the replacement (17 pounds) as I happened to have one on hand. It is noticeable, but the loss of performance is more then offset by the ease of driving around town and when I get stuck in traffic. When I am done with school and have the time to start AXing the car, I might find myself wishing for that lighter flywheel again.