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Aluminum Flywheel

Posted By Richard Last Month
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Richard
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I bought an NOS Schafer Aluminum Fly wheel specifically for the Y  Block.  What are the advantages of using a lighter flywheel.
I assume it will rev up quickly. Will this have an affect ignition and carb.   
Dobie
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I don't think it will affect ign and carb, but you will lose some low end torque. May not be a problem depending on the weight of your car/truck.
charliemccraney
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A flywheel stores energy.  A heavier flywheel stores more energy and a lighter flywheel stores less energy.  As such:

A heavy flywheel is good for towing or a heavy street vehicle and can be a benefit in drag racing.  A light flywheel is good for a light sporty vehicle where an ability to carry or pull any significant load is not needed and for road racing where the engine is mostly at mid to high rpm and getting the vehicle moving isn't as much of a concern as it is with drag racing.

I would imagine that if the engine accelerates significantly faster, then the tune would need to be revisited but I do not know if that to be true.


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55blacktie
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It will accelerate/decelerate faster, but you probably won't like clutch engagement from a dead stop. A better option for the street might be a lightened billet-steel flywheel. you might ask why aren't production vehicles equipped with aluminum flywheels, if there is an advantage on street-driven vehicles. If you go the aluminum flywheel route, buy one that uses thicker iron/steel plates and has been properly balanced. For racing, smaller-diameter flywheels/w multi-disc clutches are often used. 
DANIEL TINDER
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charliemccraney (2/11/2021)
A flywheel stores energy.  A heavier flywheel stores more energy and a lighter flywheel stores less energy.  As such:
A heavy flywheel... can be a benefit in drag racing.  


I’m confused.  While a heavy flywheel might get you off the line quicker (assuming your tires actually do hook up when the clutch is dropped at peak RPMs), wouldn’t accelerating up through the gears faster, likely more than make up for any initial bogging due to a lighter flywheel?

6 VOLTS/POS. GRD. NW INDIANA
Richard
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The Schafer Flywheel has a steel face and Not sure the weight differences. Instructions say use high quality bolts.  I think ARP.
my plan is to use a McCloud pressure plate and clutch.  I have to pull the T85 O/D to count the shafts splines or I might have a picture of the rebuild.
Richard
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I just read that an aluminum flywheel can free up horsepower. Also my Y Block has plenty of torque.
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Richard.  An aluminum flywheel generally is not recommended for street driven cars because of the issue of it not storing adequate energy for easy start-up from a stop for most vehicle applications.  You're likely to end-up having to slip the clutch for starting up from a stop light even on a level surface.  Something like a T-bucket roadster, I suspect, would not have a problem with a y-block in it having a light weight flywheel..

To compensate for the lack of stored energy needed to easily move a heavier vehicle (full-size car, station wagon, truck) from a stopped position, you could give thought to changing the ratios in your standard transmission, and / or changing your rear end gears, and perhaps changing rear tire size to dial things in.

A five speed transmission like a T-5 (many 1st gear ratios possible) or a 4 speed with the appropriate 1st gear ratio would make a big difference for stop and go city driving using an aluminum (11 lbs.?) flywheel.  Changing the rear gear ratio could be a big game changer for starting up from a stop with the aluminum flywheel.

My recollection with the B-W T-85 3 speed transmissions is that there are few options in cluster gear ratios.  A T-85 with the R-11 overdrive can make the use of the necessary 4.11:1 or 4.27:1 rear end gears work adequately for overall drive-ability.  I think that Carl in Ohio recently indicated that he has a 4.27 rear end assembly available.  I've gotten a number of parts from Carl and always found him great to work with.

An aluminum flywheel should certainly help with your vehicle's ability to accelerate more quickly once it's moving!  Hope some of these thoughts help you!   Smile

Regards,


NoShortcuts
a.k.a. Charlie Brown
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Ted
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The rule of thumb for a street driven vehicle is for the flywheel to be 1% of the car weight.  If the car weighs in at 3200 lbs, then the flywheel needs to be in the neighborhood of 32 lbs.  On a street driven vehicle with an aluminum or light weight flywheel, the engine rpm must be up more to simply get the vehicle moving versus what you see with a heavier flywheel.   As Charlie B. brings up, aluminum flywheels can be finicky to drive on a street vehicle.
 
While an engine may seem to be more responsive when winging the throttle with an aluminum flywheel versus that of a heavier flywheel, once you throw the total weight of the vehicle into the equation the actual acceleration characteristics do not change much.
 
Aluminum flywheels do shine in those instances where ‘take off’ is not a major concern such as in circle track or oval racing.  In a circle track vehicle, an aluminum flywheel does slows down that vehicle much quicker as a result of not having to shed the stored energy that’s would be in a heavier flywheel.  A good launch or take off becomes increasingly more important where clutch take offs are common such as in drag racing and/or just typical street driving.  This is where a heavier flywheel becomes much more important.  Getting back to Daniel’s question, if a vehicle bogs off of the line when taking off as in the case where an aluminum flywheel is used, then that becomes too much to overcome even with what seems to be a faster revving engine in a short period of time such as in a drag race.  But as I mentioned earlier, the weight difference between an aluminum flywheel and that of a heavier steel or cast flywheel is minimal and it will be unusual if that difference is as much as ½% of the vehicles total weight.
 
A case in point is a FE powered ’67 Comet I use to drag race; 4 speed with 5.14 and 5.43:1 rear gears.  With the aluminum flywheel the car would pull both front wheels off of the ground when launching but would immediately lose engine momentum and fall flat in performance after that initial launch.  When a 50 lb flywheel was installed, it would not only pull the wheels when launching but would carry them though most of low gear and then pull the wheels again on the second gear shift and/or rebound.  The ET for the 50 lb flywheel was quicker than the aluminum flywheel which goes back to that bogging scenario killing the 60’ times which are so important in drag racing.


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Great information Ted. Now i know why my other vehicle falls on its face unless i keep the rpms up. 

Located in Harford County Maryland 


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