Light Flywheel Performance

[byunique]

I have been debating over whether to spend the cash for a light flywheel, such as a Tilton, HKS, something in the sub 10 pound category.

I have a moderately warmed over 280, triples, 284/294 camshaft, 5speed, 3.90, shaved flywheel (approx 22 lbs.) primarily a weekend car. I am not big into drag racing, but rather into slalom and track events.

The car idles well at 800-1000rpms, not bad...

So, is it worth the cash for a approx. $350 flywheel and the labor installed. I expect faster acceleration, lightning engine response. My car will still idle right?

[2ManyZs]

If you already have a shaved flywheel I kinda doubt you would get the kind of performance gain you could really feel. I may be wrong but for the money I doubt the benefit would be worth it.

As a side note, most people recommend using a Centerforce clutch (or any other brand) with a higher clamping force to use the benefit of having the lighter flywheel ( at least over a stock one) so right there your cash outlay just about doubled. Since you say you don't race the car all the time it would be my opinion to stay with what you have, as long as it works well for what you need why change it?

[Royce]

What do you mean by a shaved flywheel, 22 lbs. sounds like the weight of a stock flywheel? Did the shave just clean up the flywheel surface like turning a brake rotor?

I am very interested in this subject and would think subracting 12 lbs. from the flywheel would make a very noticable difference. I also have a hard time justifying doing it but I am going to be changing my trans one of these days and thought it might be a good idea to do then.

Anyone have any luck lightening a stock flywheel? I would think it would have to be done by a pro since it is a cast piece. But I have a couple flywheels laying around and might let the local performance machine shop take a shot at it.

Anyone else!?

[Phred]

I just lightened a stock 1980 ZX flywheel. It started out at just over 24 lbs. I suppose they vary a bit, depending on the casting and how much was factory balanced out of it. So when you talk of a shaved fly at 22 lbs, it probably had the easy weight taken off. There's a lug of material just behind the ring gear thats easy to machine off, and its about two pounds or so. After that, you have to start being more of a machinist. (which I am) I was very conservative, and took out 6lbs. for a total weight of 18lbs. The Centerforce Dual Friction clutch weights 10 lbs. I saw a 12 lb. cast fly, and it scared me. Lite steel is good. lite cast, bad. has to do with metalergy and strength of materials. Just for comparison, a Cosworth BDD Formula Atlantic engine uses a steel fly on the order of 5 to 7 lbs. and they commonly shift at 9,500 to 10,500 RPM. and I havn't seen one fail in Twenty years.

[byunique]

If the stock flywheel was 24, then I must be wrong. Its been a long time since the flywheel was shaved, but it is noticeably lighter than stock. Don't know why I have 22 lbs stuck in my head.

[2ManyZs]

byunique,

Take a look at look at this link to the Datsun Garage. It might help you decide if you really want a lighter flywheel or not. Personally in a car that is not an all out race car I don't see any benefit.

http://geocities.com/zgarage2001/engine.html

With the money you save you could always go to a lower ratio rear, say a 4:11 or 4:37 if all you want is a little quicker acceleration while maintaining the driveability of the car. Yes, a lighter flywheel will reduce the rotational mass and allow the engine to rev quicker but it's not going to be of that much benefit since I doubt you are going to turn 7,000 plus RPM's. There will be a lot of people who disagree with me, this is just my opinion, it's your car, so perhaps you need to look at the info and decide what's right for you.

[John Coffey]

I ran a modified Tilton 8 lb. aluminum flywheel on my BSP 240 for years. For a daily driven street car I would not run something that light but for a track car its well worth the money. I would also run a Nissan Motorsports clutch and pressure plate.

And yes, the car will idle just fine - engine don't need a flywheel to idle. My new engine has a Quartermaster 5.5" multi-disk clutch and no flywheel and it idles fine.

[techart1]

Hello, I love my lightened stock flywheel, my Z is a 1970 with 2.4 bored .040, E31 w/ 280z valves, 480 lift,280 dur. bumpstick, twin stock carbs, 3.90 rear end, early 280Z 5 speeder,headers,2.5 inch freeflow exhaust. I believe that the stock early flywheel is 22 pounds, had it shaved and now it weighs 16 pounds. Had it weighted at the machine shop. A lightweight flywheel is not worth the time or money if you don't like a racy feel and if you don't like to get it on all-the-way and really drive it. I'm not saying U always have to drive like that all the time, but it's a special feeling when I want to drive it that way. And I positively Luv it. Going thru the gears is much better, you can feel the engine rev faster at all points on the tachometer, all the time, it's great I enjoy burning rubber too. Less time spent accelerating the motor means the engine is revving higher and faster and that means seeing Higher horsepower in less time. There was an article in Circle Track documenting the effects of lightened parts in a motor,like a flywheel, they even prove how this can be calculated in actual distance, actual distance your car could be Farther down the track in the same time. My Motor seems to be Happier revving it's little heart for me. The motor is less burdened at higher RPM's. We are talking about Inertia and anything you can do to make the engine change rpms faster is good. Incidentally, my Z has the early lightweight crankshaft (has been know to fail at revs over 8,200rpms) and you know what, they had to shave the counterweights to balance the motor. Pity more weigh came off the crankshaft, cuz now the rotational weight is less. Heck, I rarely spin my Z over 7,000 rpms. just once spun it up beyond 7,600 rpms, and it felt fluid , like an electric motor. Also, need to say I got the Nismo competition lightweight single groove steel front pulley from Rebello. Even that little $120 piece makes the engine rev differently, rev better.

Trade offs: In the beginning, the take off is a bit tricky, but you get the hang of it and learn to press down on the gas pedal a bit more. Be a learner not a moaner, adapt and enjoy the pleasure. Tach it up and let it out, feel the power. he he he . I'd love to have the HKS 10 pound flywheel or the Tilton piece, heard it's a jewel.