Hi guys - since I need to basically remove everything down the flywheel anyway to install the M41 on the formerly automatic car, any thoughts on lightening the flywheel?

Good idea/bad idea? How much? Where?

Thanks!

What do you use the car for?

If it spends 100% of it's time as a race car, then yes.
If it spends 100% of it's time on the highway, then no, especially if you are fond of overdrive.

Do you have other, better places for that money to go to in the car? If you are looking for bang for the buck, a decent exhaust system or cylinder head modifications can actually pay for itself.
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Three 164's, Two 144's, One 142 & a partridge in a pear tree.

Hey Tom,

Lightweight flywheels do help rev faster as they remove rotational mass from the engine, however, they also remove momentum from the engine. If you have a stock engine (or mostly stock), then just resurface/balance the flywheel is best. If you're modifying and for example want to take advantage of your headwork and cams, then yes, a flywheel can help there. In short, lightened flywheels on stock engines tend to bog on take offs and not much is gain on top either – overall, drivability is adversely impacted. Again, a great idea (when done right) on modified engines.
If you decide to go lightweight, I would suggest that you just have the stock one lightened by a decent shop if you're going for performance. Most companies charge you $300+ for a lightweight flywheel and the gains are negligible. Rebuilt SUs, Cams and headwork are a lot more important and should be done first...

Cheers,
Marco

I've lightened at least ten flywheels for various engines I built for myself and customers. None exhibited any adverse effects, only better response and acceleration. Volvo used excessively heavy flywheels to improve idle quality. Common trick among manufacturers, including Toyota.
As to cost - one hour on the big lathe, $50.00. Balancing at a specialty shop $35.00. Normally the balance is very close unless a lightening hole was removed during machining. Not a big deal.

Maybe after balancing the flywheel have them bolt up a new clutch cover and do it again but taking the unbalanced weight correction off the cover. Covers are usually balanced rather crudly and you'll see an extra hole around the edge where they've done this but it might be out enough to negate some of the good work they've done on the flywheel. I agree with Rhys and was going to suggest about 3 lbs, it does make the engine feel more lively and fools you into thinking you've got a bit more power.

I agree. You can't safely get enough mass off a stock flywheel to have any adverse effects. Four pounds off is about it, but even at that the improvement in throttle response is noticeable.

Always a good idea. Remove material at the rim, behind the ring gear, down nearly to the clutch cover bolt holes. Figure about four pounds. Makes a world of difference in throttle response.

OK - one more thing on the list :-)

Thanks Rhys.