Lightened flywheel when I re-build my engine?

[marc silva]

Is it worth it to use a lightened flywheel? I am re-building an engine and have a lightened flywheel. Do I use it or not? Pros and cons if any? I plan on using a stock clutch. Thanks

[V4F]

just take 20# off & balance . use the v8 clutch which takes machining first .

[Dave in MN]

Originally Posted by marc silva

Is it worth it to use a lightened flywheel? I am re-building an engine and have a lightened flywheel. Do I use it or not? Pros and cons if any? I plan on using a stock clutch. Thanks

I personally like a lightened flywheel. It shifts slightly quicker since the engine speeds up and slows down more rapidly when varying the fuel input. From my experiences: I can't think of any "cons" to lightening the flywheel but maybe the cost to do so. Wait...you said you already have one lightened...so only the cost to balance the assembly.

IMO: It's worth the effort to balance your rotating components. Since you are rebuilding your engine, take your crankshaft, the lightened flywheel and the pressure plate to the balancer. Have them check the balance of the flywheel as a single component. Then have them balance the crank and flywheel together then add the pressure plate and have them make any final adjustments to the pressure plate. Make sure they mark the assembly position of the flywheel to the crank and the pressure plate to the flywheel when balanced. The assembly needs to be installed exactly as it was balanced

Enjoy your new engine!

Good Day!

[Purdy Swoft]

A lightened flywheel probably gives the most noticable improvement, second only to a higher compression head. A lighter flywheel probably doesn't add any horsepower but gives quicker throttle response and faster acceleration. The engine spools up and down quicker, Up for quick acceleration and down for easier gear shifts without as much clash. When the engine is shut off , it quits right then instead of free wheeling like a worn out engine. A lighter flywheel removes weight from the main bearing cap babbit for longer bearing life. I personally like the model B flywheel, Its about 18 lbs. lighter than the model A flywheel (mine is ) and uses the same clutch. The B flywheel was done at the factory, is lighter and doesn't run the risk of being an unbalanced or a botched up job like some that i've heard about. They don't idle quite as slow but mine will still chick ah lunk with the spark retarded. I'm more interested in driveability and a quicker responding engine than the very slowest idle.

[Patrick L.]

' chick ah lunk '
LOL ! I like that.

[28ACoupe]

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The only thing a lightened flywheel does is allow for quicker revs out of gear. It does not create any horsepower. You may get up to speed a bit faster on flat ground, however, you will also lose speed faster on the hills due to the lack of energy stored in the rotating mass.

This is simply physics. There is always a trade off.

[Purdy Swoft]

Sometimes it depends on where the model A is from. In Cal-ah-phone-ya, they say ta da ta da ta da ta da or so says the assistant guru of stuff, Bill W. I won't repeat what Vince says that they say. I think that many have a different opinion on what the model A is saying when it idles with the spark retarded.

[BILL WILLIAMSON]

Originally Posted by Purdy Swoft

Sometimes it depends on where the model A is from. In Cal-ah-phone-ya, they say ta da ta da ta da ta da or so says the assistant guru of stuff, Bill W. I won't repeat what Vince says that they say. I think that many have a different opinion on what the model A is saying when it idles with the spark retarded.

Slight correction, Bro Purdy: Minerva sed, TADA-TADA-TADA-TADA, except once when a plug wire fall off, then, TADA-TADA--------TADA!
Soon as Vermin's fired, I'll report whut he sez! They ALL "TALK" diffurent! (REALLY!) Bill W.

[Terry,NJ]

My reasoning, (be it ever so humble) is that it "Frees" up horsepower while accelerating. I lightened mine about ten lbs (Not much really) and it just seems more powerful. If you can do it cheaply, I'd recommend it. The actual turning cost me nothing, I used a friend's lathe, but the balancing cost me $60. For a practical demonstration, Go outside and flip a stock FW (63lbs) around. then try it with a lightened FW, Takes a little less strength, doesn't it? Engineers of the 1800s loved heavy FWs. They evened out all the bumps, pulses. lurches, etc that machinery hed to deal with. As newer cars were produced, FW weights went down. This was because of better road conditions and better fuels and more powerful engines. Yes, Cut it down!
Terry

[28ACoupe]

A lightened flywheel doesn't free up anything. It only doesn't store as much energy as the heavier units. You won't go any faster. If your car will only do 60mph with a full weight fly wheel, then it will only go 60mph with a lightened one.

When I was building racing engines, we used lightened flywheels. However, these engines made more than enough torque to offset any loss of stored energy in the lighter units.

Sadly, this is more butt-dyno nonsense.

[Purdy Swoft]

28ACoupe, You are really showing those of us with experience, what you REALLY know. Tractors and such used heavy flywheels. The stored energy in a heavy flywheel translates like this. The heavy weight fly wheel in motion gives more low speed pulling power. Tractors need low speed pulling power , At the times that the model A was used roads were very poor.. A light flywheel allows the engine to accelerate and decellerate quicker. Instead of making horsepower, the lighter flywheel lets the engine RPMs increase quicker .The engine produces more horsepower at higher RPM. If you had any racing experience you would understand this. Stall speed converters are used with performance applications for the same reason. The reason being to get the engine turning enough RPM to produce more horsepower. w It has the same effect of useing a lower gear to get RPMs up where horsepower increases. And No, a light flywheel probably doesn't add any horsepower, It helps increase RPMs Besides giving more pep and passing power, the lighter flywheel makes a big difference in clash free gear shifts. Without all of the spinning weight of a heavy flywheel pushing it, the engine decellerates quicker causeing easier shifts. A lighter flywheel takes weight off the main bearings. I can't see a single bad side effect.

[28ACoupe]

Go back to school Purdy. Study physics.

[Wallace]

It appears that you two are saying somewhat the same thing. let's lighten the flywheel ...driving conditions have changed and the features the A needed in its useful life are significantly different now when it is the focus of a great hobby.

[Purdy Swoft]

As long as you are happy with what you think that you know, its fine with me

[28ACoupe]

Facts:

1) a lightened flywheel will not create any more power. To do so requires energy to be converted and this is not what a flywheel does.
2) A heavy flywheel stores energy which can be released when needed in the form of more pulling power on a hill or other such situations.
3) A lightened flywheel will allow an engine to rev faster if, and only if the engine is capable of gaining speed at all under that particular load.

On flat ground, yes, you will get to speed a little faster. However, there is a price to pay for this.

These are facts as required by the laws of physics. If you want to go faster in your Model A, you need to modify the entire system the same as any other engine. Just changing one thing might make you feel better, but you won't gain much.

This reminds me of the guys who go out and buy an aftermarket intake and huge carb for their engines and then think they are somehow going to go faster. It doesn't work that way.

[Pete]

Originally Posted by 28ACoupe

Facts:

1) a lightened flywheel will not create any more power. To do so requires energy to be converted and this is not what a flywheel does.
2) A heavy flywheel stores energy which can be released when needed in the form of more pulling power on a hill or other such situations.
3) A lightened flywheel will allow an engine to rev faster if, and only if the engine is capable of gaining speed at all under that particular load.

On flat ground, yes, you will get to speed a little faster. However, there is a price to pay for this.

These are facts as required by the laws of physics. If you want to go faster in your Model A, you need to modify the entire system the same as any other engine. Just changing one thing might make you feel better, but you won't gain much.

This reminds me of the guys who go out and buy an aftermarket intake and huge carb for their engines and then think they are somehow going to go faster. It doesn't work that way.

Re #2. But only for a VERY short interval of time.

The heavy flywheel makes for slower idle is mainly because the engine won't idle smooth with no flywheel due to poor tuning.
I have demonstrated several times that a stock engine with NO flywheel can be made to idle smooth at 400 rpm.
On many of the modified street engines I built, I used an 11 lb small block Chev aluminum flywheel and an 9 inch aluminum clutch cover from a flathead Ford V8. The clutch cover weighs about 10 lb.
Even with a 404A radius lifter racing cam, these engines will idle at 600 rpm with just a slight lope.
Those that saw me at the 2002 Riverside MAFCA national meet can attest to this.

I love the signature someone on here uses that pertains to all this.

"Just because you don't believe in the laws of physics doesn't mean they don't apply to you."

[Patrick L.]

I'd like to know the magic number from those that have experienced different weight wheels. I like the all the energy that big wheel has and am thinking of a lighter wheel when the engine is redone, but, don't want to go too light.

[Dave in MN]

Originally Posted by Patrick L.

I'd like to know the magic number from those that have experienced different weight wheels. I like the all the energy that big wheel has and am thinking of a lighter wheel when the engine is redone, but, don't want to go too light.

I like removing 12 to 17 pounds. If I am adding counterweights to a crank, I will remove 17-20 lbs from the flywheel.
When lightening, have the machinist check the working face of the flywheel alignment to the crankshaft mounting surface to make sure it spins straight. We don't want wobbles!

Others may suggest differently...

Good Day!

www.durableperformance.net

[CarlG]

My complete assembly: Flywheel, Clutch plate & Pressure Plate weighs 20# less than the original I took out. (using the bathroom scales)

[Kahuna]

I don't think you can go too light. I once had a Weber flywheel that weighed 12#. The pressure plate probably weighed as much. Car drove fine.
Plus, less weight on the main bearing.
JMO