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Flywheel Balancing
Posted by: Michael Marotta ()
Date: February 22, 2005 08:15AM

Whenever you replace your flywheel does it always need to be balanced? Also how much does this usually cost?

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Flywheel Balancing.... a Necessity
Posted by: Chet Reed ()
Date: February 22, 2005 11:42AM

Every rebuilt flywheel that I receive is dynamically balanced along with the clutch plate; both are balanced as a set. Rick's Machine in Santee, Ca. charges approximately $40 for this service.
Cost of balancing of reciprocating and rotating parts will vary greatly.... depends on prevailing shop labor rates. Expect to shell out anywhere from $35 to $75 to balance a flywheel with clutch plate.
It is wise to dynamically balance any replacement rotating or reciprocating component, especially a flywheel due to imprecise method of static balancing when rebuilt.

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Re: Flywheel Balancing
Posted by: "UNSAFE" ()
Date: February 22, 2005 12:30PM


Chet Reed is right about balancing !

I use Dale flywheels (scalloped) and have them balanced along with the rotating engine parts.

Having said that :--------

You could probably "get by" without balancing the flywheel.

I have "just" swapped flywheels in the past with no noticable ill effect.

It's possible that your replacement flywheel is already right on and needs no adjustment, or vice versa. Do you feel lucky?

Some bolted vendor replacements are balanced.

I think balancing is more critical on higher rpm applications.

What motor do you have?

Just my opinions.
"UNSAFE"

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Re: Flywheel Balancing.... a Necessity
Posted by: Michael Marotta ()
Date: February 22, 2005 10:21PM

I have a 65 140 w/ OT-20 cam and many extras

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Re: Flywheel Balancing.... a Necessity
Posted by: "UNSAFE" ()
Date: February 22, 2005 11:00PM

Michael, If you like lots of rpms, you should have the flywheel balance checked.

Have you considered a scalloped(lightened) flywheel ? Free horsepower !

I used one in my Sprint with a motor set-up similar to yours.

I use one in my big bore motor also.

"UNSAFE"

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Re: Flywheel Balancing
Posted by: Michael Marotta ()
Date: February 23, 2005 04:38PM

Do you feel that the advertised bogging from a start is worth the quicker acceleration?

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Re: Flywheel Balancing
Posted by: Larry Forman ()
Date: February 23, 2005 05:02PM

Michael,
Engine bog is cured with your right foot. I don't think YOU will have any difficulty in that area. I suppose I could always check with the Rocklin PD. LOL.
-- Larry

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Re: Flywheel Balancing
Posted by: "UNSAFE" ()
Date: February 23, 2005 06:33PM

>>>Do you feel that the advertised bogging from a start is worth the quicker acceleration?<<<

Sounds like a trick question the way you worded it.

Does this explain it ? >>> ½MV² = ½V² + ½(VGr/R)² =>
½MV² = ½V² + ½V²(Gr/R)² => divide both sides by ½V² to arrive at the final equation:
M = 1 + (Gr/R)² .

Me neither , ggg, but a good explanation can be found at

[www.pumaracing.co.uk]


Anyway, in MY opinion there is very little noticible "bogging" with a light flywheel.

If you didn't know how to use a clutch, the heavier flywheel might prevent the engine from dying when you "popped" the clutch.

I believe it makes high rpm shifting better.

The engine with gather revs quicker and slow back down quicker as well.

Engine "braking" during downshifts will improve.

The faster you spin you motor, the more the light flywheel helps.

It has more effect in the lower gears.

It will improve acceleration !

A couple pounds off the flywheel is about like taking two hundred pounds out of the car in regards to lower gear acceleration.

Quote: "When the flywheel of a car is lightened it can have a great effect on acceleration - much more than just the weight saving as a proportion of the total vehicle weight would account for. This is because rotating components store rotational energy as well as having to be accelerated in a linear direction along with the rest of the car's mass. The faster a component rotates, the greater the amount of rotational kinetic energy that ends up being stored in it. The engine turns potential energy from fuel into kinetic energy of motion when it accelerates a vehicle. Any energy that ends up being stored in rotating components is not available to accelerate the car in a linear direction - so reducing the mass (or more properly the "moment of inertia") of these components leaves more of the engine's output to accelerate the car."


Just my .02
"UNSAFE"

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Re: Flywheel Balancing
Posted by: WALT ()
Date: February 23, 2005 06:59PM

DO YOU STILL USE THE HEAVIER PRESSURE PLATE THAT WAS STANDARD ON THE 140 AND THE TURBO?

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Re: Flywheel Balancing
Posted by: "UNSAFE" ()
Date: February 23, 2005 07:42PM

Currently I am using a HD weighted pressure plate from the Source with a Kevlar disk but plan on using the lighter (non-lugged) version on my next clutch job or when I reinstall my 4.11 gears.

On my Sprint I used the light( Dale scalloped) flywheel and the light clutch cover with heavy duty springs and liked it fine.
Some vendors sell an even lighter "Yenko" version.

I have never run any gears less than 3.55 though.

Driving styles vary and I am into RPMs.

The only time I have really noticed a bogging problem was when I installed a double-close ratio transmission with a 2.20/1 first gear. Even with the 4.11s it was way too much first gear for the street, or any kind of drag racing.
Heck, I would about toast my clutch just trying to get up my driveway !

Pic is of a standard bore piston in a 94mm (190cube) cylinder.

"UNSAFE"

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Several Flywheels
Posted by: Larry Forman ()
Date: February 23, 2005 09:27PM

Hi Kevin,
Excellent description of flywheel effects. What many people don't realize, and the SUV people are the WORST in this regard, is that you have several flywheels in the form of your wheels and tires. The HUGE SUV wheels and tires are STUPID, IMO. That is why I am going to extremes the other way in the Devin C to use small 13-inch tires and superlightweight wheels. That way I don't have the effect of having to rev up four extra flywheels plus the commonly assumed one. It also helps in stopping the car faster. I also have a special pressure plate made of the lighter pressure plate, but with heavier springs to reduce the rotating weight in addition to a lightened flywheel. It is difficult to remove an excessive amount of rotating mass.
-- Larry

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Re: Flywheel Balancing
Posted by: Michael Marotta ()
Date: February 23, 2005 09:36PM

Well,

The verdict is in. I'm gonna buy a lightened flywheel and possibly one of these "light" pressure plates you speak of.

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