Lightened Flywheel

[Paul Sj]

I am in the middle of a complete rebuild on my BN7 engine. I am considering a lightened flywheel. Does any one have any experience or recommendations? At $600+ I am wondering if it is worth it. How about a harmonic balancer? Are they worth the money?

Thanks,
Paul

 

[Dave Russell]

Paul,

A light flywheel will make the car "feel" more racy. When the engine is not loaded such as in neutral or when the clutch is disengaged. Kind of fun to have the quick engine response. (Rev quicker when you blip the throttle) As far as increasing acceleration, put into perspective, consider that with the engine connected to the car, you are trying to accelerate the whole drive train rotating mass - wheels, tires, axles, transmission, plus flywheel, which all together could weigh around 120 lbs. A reduction of 20 lb on the flywheel is not a large gain. The gains will be greater in the lower gears & less in top gear. This is a great over simplification but shows the point. It will not greatly improve performance but is fun to have. In a race car where it is important to have quick revving between shifts & the last little bit of engine response it is an advantage. The down side is that it is harder to get the car rolling without stalling. If I had the flywheel out of my car & had the money to burn, I would probably do it for the "fun" factor.

The harmonic balancer may increase engine life if you are running over 4500 rpm a lot but not much for normal driving. Again, an advantage in a race car.

D

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Paul Sj:
I am in the middle of a complete rebuild on my BN7 engine. I am considering a lightened flywheel. Does any one have any experience or recommendations? At $600+ I am wondering if it is worth it. How about a harmonic balancer? Are they worth the money?

Thanks,
Paul<hr></blockquote>

 

[BEEJAY7]

paul

The answer is "yes" and "yes".....The whole drivetrain is much, much smoother and free reving.
The harmonic balancer will require some modification to the front crossmember to fit.

See Denis Welch's website for some really neat flywheels and balancers, (but don't look at the prices!)

see www.bighealey.co.uk

cheers

 

[DougR]

I would consider BALANCING the crank, pistons, and flywheel assembly without necessarily lightening the flywheel. The quick throttle response (of lightened flywheel) is fun but, as mentioned earlier, there are other sacrifices.
Other than lightening the wallet, I see no downside to the balance program.

 

[w. scott brunkhurst]

My car came from the competition works in Warwick. Though it wasn't specified on the order sheet, they put in a lightened crank shaft, but not a lightened flywheel. I am assuming that they didn't feel it was really necessary.

SB

 

[Paul Sj]

Thanks for the input. Based on the kind of driving I will be doing, I think I'll wait for now and spend the $ on less optional parts of the restoration.

Paul

 

[Scooter]

Hi Paul,

When the time comes, you might try contacting Bill Bolton at TriCarb@aol.com He's a great guy, and performs this service.

My BN4 came with a lightened flywheel that was already machined from the original. It may increase throttle response, but it will decrease low end torque due to less mass. There is also a safety factor when lightening the flywheel because if too much material is removed leaving a narrow cross section, it can be dangerous if it were to shatter. So make sure you don't sacrifice safety, and be sure whoever performs the job uses a known profile.

You can see the flywheel that came with my car at:

https://users.arczip.com/zntech/flywheel.html

Scooter

 

[John Turney]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Scooter:
Hi Paul,

So make sure you don't sacrifice safety, and be sure whoever performs the job uses a known profile.

You can see the flywheel that came with my car at:

https://users.arczip.com/zntech/flywheel.html

Scooter<hr></blockquote>

Scooter, Like your photos!

I had my flywheel lightened by Denis Welch, and am happy with it. If you decide to send anything to the UK for work, make sure you state on the customs form that its "for repair and return." Her Majesty will extract a hefty price if you don't.

John, BN4

 

[Gary Lloyd]

I have never lightened a flywheel, but I do balance every engine I build, bit Chevy, Ford or MGB, I would think it would really be worthwnile in a Healey!! And the really good thin, balancing is really cheap!!

By the way, I have never built a Healey, or I would have balanced it for sure!!

 

[Jim MacDonald]

I would not lighten the fly wheel. I did it on my Triumph TR250 years ago and would not do it again. The flywheel serves a function of smoothing out pulses between combustion cycles. At higher revs it's not as much an issue but at or near idle the car will run rough.
At a minimum you must have the flywheel dynamically balanced if you do choose to lighten it, but again I would strongly recommend against it.

 

[RF Thom]

Another negative to consider, is yes the mass removal means that the engine will accellerate at a faster rate and remember the clutch is the centre link transmitting all the torque to the transmission. This faster rate of change of accelleration CAN overload the closed clutch causing slipping and burning. I've workrd on engine/trans designs where we put mass into the flywheel to ensure validation of the clutch for just such a failure mode. Remember that racers do this but also utilize a racing clutch which is designed to handle higher torque loads. When rebuilding my Healey engine I did put the flywheel in the lathe and took 18 Lbs of cast iron off the back, but being aware if the limitation I never power shift the trans, but once in gear - look out.

Regards, Bob