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Discussion Starter · #1 ·
I'm looking for some input from the collective wisdom here on the AlfaBB. I'm freshening up a 2L engine that currently has a lightened flywheel. The stock flywheel was machined down to 7kg/15.6lbs a long time ago. I see there's vendors that have lightened flywheels available for the street weighing ~6.1kg/13.4lbs. I don't think the improvement in mass would be worth the upgrade for a street car that gets the occasional brisk run through the mountains or driver's event.

What do you all think? I've been running this flywheel for so long that its just normal to me. Would an additional ~1kg/2lb weight reduction be noticeable and/or worth the incremental cost? I'm leaning toward no, but would love perspectives from the community.

Regardless of which I go with, I'm going to have the rotating bits balanced.

Thanks
Lawrence
 

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Richard Jemison
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You don`t say what application it is... A 105/115 flywheel is by design heavier than 116 flywheel.
If it is one I built it has already been balanced after lightening. On a 2 liter 115 type 15+ lbs including the ring gear is about the limit for safety.
 

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Discussion Starter · #5 ·
You don`t say what application it is... A 105/115 flywheel is by design heavier than 116 flywheel.
If it is one I built it has already been balanced after lightening. On a 2 liter 115 type 15+ lbs including the ring gear is about the limit for safety.
Thanks Richard - it's a 1750 GTV and I'm dusting off my old twinspark.

It seems the decision is made to stick with what I've got.
 

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As you can see, the flywheel currently on my 78 Spider weighs about 14 pounds.

I've used lightened flywheels on Datsun 610, stroked Datsun Z motor at 3.0L, stock Datsun Zs, VW bugs, 79 Spider, 78 Sport Sedan, Mazda Miata, and a few more I can't recall. Nice mod.
 

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My seat-of-the-pants empiricism tells me that I probably couldn't tell a 2 lb difference in flywheel weight in two similarly built Alfa engines.. When we built my 2 liter that's in my Super, I chose a purpose-built AH lightwight steel flywheel @ 13.4lbs. It's a nice piece of kit, came with a new fitted ring-gear and fit perfectly. Is it "better" than a professionally lightened stock flywheel like Richard's? Probably not. (It's also worth noting that there are lots of full-tilt Alfa race-cars running properly lightened stock flywheels.) I don't think I've ever driven a stock 105 Alfa with a light flywheel so perhsps others can comment on that experience. What really counts, IMHO, is building a 105 motor with a fully balanced---crank, rods, front-pulley, pistons, light flywheel, clutch---bottom end. You'll often hear arguments that this is overkill on a street-driven Alfa motor but, following David Vizard's long ago advice, I've found that the discernable tactile difference between stock and balanced is what makes runs through the Hill Country just that much more enjoyable.
 
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