Just though I would list my recent experience with an ally flywheel weighing 12lbs behind an 8ba, edelbrock heads, 2x2 intake fitted in a model a roadster at 1900lbs. all I can say is that it’s spot on! Yes I have the ideal car at 1900lbs, with 4.1 rear gears and a t5 trans. I can pull away in second with no throttle! It picks up quicker and no ill effects on engine braking. I’m sure if you have a 3 speed and/or heavier car it could be worse. But if not I say go for it!!
Sounds cool but I read they don't last long because the surface galls really bad? I.e. good for racing but not for street and stop-n-go traffic?
Run a 14 lb aluminum with steel insert on my 29 roadster. No issues in 20,000 miles. Blown 276 59ab, t5 with 2.95 first gear, 4.11 Traclok rear end.
I'm running a 239 with an Isky 88 cam, high rise dual carbs, headers, aluminum heads, and a steel insert aluminum flywheel. It makes for a really snappy motor in my roadster with 4:11's. Not sure I'd use it in a fat fendered car with a flathead. I had reservations about using an aluminum flywheel with a 331 Cadillac in my '40, I was worried about losing torque. Boy was I wrong, no issue there either.