Technical Cutting the fly wheel...

I'm getting ready to pull my motor and instal a new clutch, pressure plate, and throw out bearing on my coupe... It's an 8ba with a duel carb intake... 39 trans, top loader, with closed drive... Pretty much a stock motor.... I was thinking about taking some meat off the fly wheel while I have it apart... I work in a machine shop and we have a few lathes I can work on... Is this a good idea or am I wasting my time... Thanks

 

They're usually blanchard ground, not done on a lathe.

 

By lightning up the flywheel the motor will rev up faster. Acceleration will be quicker as long as you have low gears. If you have high gears for the highway you will be going backwards and will lose acceleration speed. Don't hold me to this but.....here's mine.

 

Some people here warn of safety issues... if it gets too thin

Speaking of lathes for cutting the "face"; I did my heavy 55 Olds wheel on my Aamco. It has a special arbor for that. The face was that choppy, burn spotted look.

I found out something I never knew about those types of burn spots; they were actually hard spots, and even a new cutter bit would bounce over them, until I did some aggressive cuts to get "under" the hard spots. I think I lost .100" off the face, before the last finish cut showed that the hard spots were totally gone.

Made me wonder that if I sent it out to be "ground" like all shops do, I bet the hard spots would still be there, but hidden.....and certainly come back after many miles of driving? Seems to me that the surface cannot wear evenly, if hard spots are still there, even though the grinding made them look gone?

 

You are correct about the cutter skipping over the hard spots. No matter what type of lathe is used.. I used to do a lot of over the road and construction trucks and .100" was the usual start of smooth.. Even then, sometimes, I would have to put the wheel on the grinder for decent finish.. Paddle clutches wear heavily on the flywheel..
A grinder just masks the bad spots and they will eventually show up again in hard use.. But it makes for a great LOOKING finished product.

I have done several cut down flathead and VW flywheels .. It depends on what the owner wants.. Big rear tires and wheels require heavy wheel..

 

thanks for backing up my unintentional "research". I almost did not post it, as I thought I'd be called a hack for not sending it out for wet grinding

 

I have 4.11 gears and running 7.00 x 16's on the rear... I'm looking to gain a little pep with out tearing apart a tight motor... I have seen guys machine out a lot of material to lighten them.. Is it worth it for a stock setup like I have or save the energy on another build....

 

Don't forget about balancing. I don't know if you just cut down the flywheel and rebalance it will work. or if you will have to rebalance the hole motor. I know some guys like to balance everything at once.

 

No has mentioned yet that if the surface has too much material removed the pressure plate will not clamp down as hard enough and the clutch can slip.

 

??? Doesn't the mounting surface get machined the same amount???

 

Whoops, brain fart, totally backwards thinking today, the clutch will not release completely due to the increased distance the throw out bearing would have to travel if it is at maximum adjustment, applies to hydraulic clutches. My bad. I'll show myself out.

 

you were correct in this first post. Some flywheels do have a raised step where the pressure plate attaches, and those steps need to be cut the same amount, to get the same clamping force

 

i did the same thing one night late, wanted to get the job done so i turned it on my brake lathe. kept cutting till the hard spots were gone. miles of hard use and off roading, it never was a problem.

 

Believe it or not am OEM flywheel has an ever so slight cone shape to it to make for easy clutch engagement . Very hard if impossible to identify by eye . Check run out with an indicator you will define the runout .

 

If you have a stock 8ba flywheel it weighs about 35 lbs
You can safely reduce it to about 22 lbs without problem.
Yes, it's a good thing to do, especially in a modified engine.

 

I had mine done. Works great and really woke the little motor up! I don't think I would like it in a heavy full body car but a little roadster it works great!
Walter

 

Lightened flywheel is an old trick for faster acceleration and faster gearshifts. The stock flywheel is heavy so Mrs Peasy Weasy can drive her stock sedan while making every mistake in the book, and still get to the supermarket without stalling the motor. Modern cars use much lighter flywheels because today we have automatics for the Peasy Weasies and manual trans for the enthusiast.