Lightened flywheel

D

dave11

Member
I finally decided to overhaul the transmission in my 30 coupe. While I had it apart I pulled the flywheel to check the runout of the flywheel housing, good thing I did as it was .015 should be .006". Before removing the flywheel I was warned that it was heavy at 63 lbs, mine didn't seem to weigh anyway near that,... so I weighed it at 35 lbs.
Just wondering...what are the pros and cons of a light weight flywheel. My engine runs great although it will not idle as slow and steady as I have heard other A's do.

Dave
 
If you have a lightened flywheel you probably have other "improvements". They all work together so I see no benefit to changing back to stock. Ron W
 
I am guessing the lightened flywheel is contributing to my idling issue,...the idle is not bad but some A's will idle down to about 3 - 400 rpm at a nice steady rythum...not mine
 
I have the lightened flywheel also. No, it won't idle down but it goes sooo much better.
Ron W
 
A heavy flywheel will cover up problems/mods.
A stock model A engine that is new or rebuilt to new specs will
idle smooth at 400 rpm with NO flywheel.
 
I would have a machine shop indicate and take a skim cut off of it to true it up and have it rebalanced. Another advantage is to the rear main bearing. It doesn't have to support the 63 lbs flywheel anymore.
Terry
 
The flywheels in my two driving A's both weight approximately 39 pounds including the ring gear.
Your excelleration will be much better with the lightened flywheel and less weight on the rear main.
Be sure they are balanced, both flywheel and pressure plate; balance flywheel first then install pressure plate and balance whole unit, the second balance work is done on the pressure plate. Using this approach will save time in the future should you ever have to replace just the pressure plate.

Ron
 
I have a lightened flywheel in mine. With a Stipe 340 cam and 7:1 head, weber carb among other things, it still idles smoothly between 300 and 400 rpm. Has great pickup too!
 
I recently went back to a stock weight flywheel on a Model A. The lightened flywheel is OK if you want a snappier throttle response. However, the Model A climbs much better with the full weight flywheel and is much easier to drive. It does idle lower and it is noticeably smoother.
 
I agree with Terry, it will rev up a little quicker and you'll notice more "pep". It doesn't do much good either way unless it is balanced. It will idle smoother and you'll have less vibration, which in turn will make your babbitts/inserts last longer as well. My .02
 
Pete said:
A heavy flywheel will cover up problems/mods.
A stock model A engine that is new or rebuilt to new specs will
idle smooth at 400 rpm with NO flywheel.
Click to expand...

Pete, I'm asking this out of mere curiosity, not to doubt you, but is there a video available of an A idling without a fly wheel? I would never have guessed that that light crank would have enough inertia to carry on to the next firing event.
Can you hand crank it fast enough for it to start? Or do you adapt a hand crank to an electric motor or something?
Thanks!
 
40 Deluxe said:
Pete, I'm asking this out of mere curiosity, not to doubt you, but is there a video available of an A idling without a fly wheel? I would never have guessed that that light crank would have enough inertia to carry on to the next firing event.
Can you hand crank it fast enough for it to start? Or do you adapt a hand crank to an electric motor or something?
Thanks!
Click to expand...

I don't know of any video and haven't looked.
Yes, you can hand crank start it.
Vintage circle track race cars seldom use a flywheel or clutch and they will idle fine even with a radical cam.
They push start.
 
I have a lightened flywheel somewhat counteracted by counterweights on the crankshaft, 7:1 head, reground camshaft, larger inlet valves and twin Stromberg carbies and it idles sweetly at 400rpm.
I think it's all down to careful tuning?
Keith
 
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