I have an 85 accord. It is an injected model. I'm planning to use as an oval track racer. I want to lighten the flywheel and was wondering where to make the cuts. I will be taking it to an experanced machinist, but not sure if he would know where to make the cut/s.

 

I believe that a lot of machinists will simply lathe down the entire thing so that it remains balanced but becomes thinner

 

Not anywhere remotely near the centre of the flywheel. Weight here has very little affect on the 'flywheel effect' (more affect with weight/ mass the closer you get to the outside edge of the flywheel, depending on juist where metal is removed you can have a heavier flywheel that actually has less flywheel effect than a lighter flywheel), but,if you machine metal away closer to the centre it will have a huge affect on the strength of the flywheel.

If a flywheel fractures it can very easily kill you, the kinetic energy embodied in a rotating flywheel (especially at higher rpm) is absolutely enormous and pieces of flywheel (or even the whole flywheel, the first motion shaft won't restrain it the flywheel will just rip it out) will go through the bell housing and firewall as if they were not even there, and literally make mincemeat of the driver if he /she is hit by any shrapnel. An exploding flywheel could also be a danger to other drivers and any bystanders.

I wouldn't have just any old "experienced machinist" do this work (no matter how experienced they may be with other sorts of work), I'd take it to someone who really understands specifically what they're doing with flywheel lightening. You want a specialist race engine builder to do or have the work done I would think, or at least to get proper advice from. It would be safer (and possibly not a great deal more expensive) just to purchase an off the shelf after market lightweight flywheel, which isn't to say that a lightened stock flywheel will be unsafe, just that it needs to lightened properly by someone who knows exactly what they're doing.

Also, don't use the dimensions of aftermarket lightweight flywheels as any sort of a guide to lightening a stock flywheel, these are typically made from a high quality steel which is muchstonger than the cast iron that stock flywheels are typically made from.

 

im a bit skeptical of flywheel lightening...
I mean flywheels are built with a certain weight for a reason...

 

Yes, to suit average drivers who want a smooth engine with good / lazy 'just off idle' torque characteristic,drive sedately mostly in city conditions, and don't really want an engine that istrigger responsive when the clutch is depressed etc. It's a lowest common denominator thing. There's nothing wrong with changing the flywheel weight so long as the result is what you want and what you expect, but like most things it's not a free lunch, it's a compromise.

Oh, and so long as lightening the flywheel doesn't make it dangerous!