[Vid]

Originally Posted by Tom Vaught

Apologize, Did not realize that you had moved up to a 9" Ford Rear like did
Tom V.

No worries Tom. The weakest link in my entire driveline was without a doubt the rear end, so the upgrade to a 9” was sorely needed. The good folks at Quick Performance are building one to my spec, which includes the 3:60’s, heavy duty center section and other goodies.


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[KEN CROCIE]

I ran a Schiefer al wheel back in ' 69. This wheel was lighter than the normal al wheel as it had an iron sprayed clutch face rather than the normal inserted iron face. Also ran a Schiefer al. pressure plate. loved it. It accelerated noticeably quicker than the stock setup. You just adapt (learn) a different driving technique. Takes about a day.

64 GTO, muncie wide, 3.23 gear, 389 tripower.

[jhein]

Originally Posted by track73

Remember the crankshaft weighs 75 pounds.

True, but the diameter of the flywheel increases the effect of it's weight exponentially (non-linear)

[Skip Fix]

Originally Posted by KEN CROCIE

I ran a Schiefer al wheel back in ' 69. This wheel was lighter than the normal al wheel as it had an iron sprayed clutch face rather than the normal inserted iron face. Also ran a Schiefer al. pressure plate. loved it. It accelerated noticeably quicker than the stock setup. You just adapt (learn) a different driving technique. Takes about a day.

64 GTO, muncie wide, 3.23 gear, 389 tripower.

5000 rpm side steps

[70GS455]

Originally Posted by Vid

So… 2.52 (1st gear) x 3.60 (ring & pinion) = 9.07. That would be a fail if I did the math correctly?


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It's close enough it should be ok. Where it matters most is racing at the strip with slicks or drag radials. On the street, it should be fine.

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[KEN CROCIE]

The Schiefer wheel was forged and not cut from plate. I think mine was 12 #. Google for images. The Pontiac forging looked like the chevy forging

[Tom Vaught]

X2 on mine being Forged. The Weber was not.

Tom V.

[GoreMaker]

There's some weird info being shared here when it comes to flywheels...

The flywheel serves to store rotational energy to overcome the inertia of the vehicle's mass at rest. You spin it up to a certain RPM, release the clutch, and the stored energy moves the car forward with minimal bogging of the engine. The heavier the flywheel, the better this works and the less RPM you need to get the car moving the way you want it to. Once the car is moving, the inertia has been overcome and getting it to keep accelerating is much easier. At that point the flywheel isn't doing much of anything except going along for the ride.

The flywheel itself is never stationary, so it doesn't provide the same inertia against the engine. It contributes some minor inertia to overcome at lower RPMs, but ultimately the flywheel is just a drop in the bucket as far as rotating weight compared to the transmission input/output shafts, driveshaft, the ring and pinion, the axles, the brakes and the wheels all combined. On a loose surface like dirt, a lighter flywheel might make a noticeable difference on corner exit. But other than that, the difference in "feel" that a lighter flywheel imparts doesn't actually translate to higher performance. It's similar to a louder exhaust... louder doesn't mean faster, and an engine that responds more quickly to throttle input isn't necessarily putting down more power to the pavement.

I've seen dyno runs where the peak horsepower rating went up with a lighter flywheel being the only change. Except that the torque curve really became more "peaky" and the total power under the curve was lower overall. Dynos don't measure horsepower, they measure torque and speed and time and use that to calculate (estimate) horsepower. So that peak horsepower gain is mostly meaningless as far as how fast the car can accelerate. In many cases, performance and efficiency will be lower with a lighter flywheel because the engine's power off the line will have been wasted, and that's where it counts the most.

There's diminishing returns there in either direction, but typically for a Pontiac V8, a +/- 30 pound flywheel is an ideal compromise for drivability, performance and driveline longevity.

[Tom Vaught]

Originally Posted by GoreMaker

There's some weird info being shared here when it comes to flywheels...

The flywheel serves to store rotational energy to overcome the inertia of the vehicle's mass at rest. You spin it up to a certain RPM, release the clutch, and the stored energy moves the car forward with minimal bogging of the engine. The heavier the flywheel, the better this works and the less RPM you need to get the car moving the way you want it to. Once the car is moving, the inertia has been overcome and getting it to keep accelerating is much easier. At that point the flywheel isn't doing much of anything except going along for the ride.

Never really needed a Cast Iron factory 30 lb flywheel, or a 40 lb steel flywheel, when I had a lighter Aluminum flywheel that was assisted by a 4.33 rear axle ratio gear. When you have a 3.23 gear and a 2.56 1st gear you don't have much "mechanical leverage" to get the vehicle initially moving.

When you have a 3.27 1st gear and a lighter aluminum flywheel the effect of the lighter flywheel is not noticeable when driving away from a stop light so I would say it depends on what you are doing with the application.

I think I have a 40 lb steel flywheel someplace (that I bought years ago) thinking I needed it for street driving.
When I find it, it will be for sale.

Tom V.

[GoreMaker]

Oh for sure the total 1st gear multiplication has a lot to do with how much flywheel weight a car needs. Depending on vehicle weight, going beyond 10:1 means less weight needed at the flywheel. But there's also barely any downside to having a 30 pound flywheel

[GoreMaker]

I'm running a 3.42 final drive with a 2.43 1st gear for a total multiplication of 8.3:1, with slightly tall rear tires on a full weight car. That seems to be a pretty typical setup for a street car. I see no reason or potential benefit to running a ligjtweight flywheel in that situation

[Tom Vaught]

Originally Posted by GoreMaker

I'm running a 3.42 final drive with a 2.43 1st gear for a total multiplication of 8.3:1, with slightly tall rear tires on a full weight car. That seems to be a pretty typical setup for a street car. I see no reason or potential benefit to running a ligjtweight flywheel in that situation

AGREE, I think needing a 10 to 1 multiplier may be more for smaller engines with less bottom end torque.

Tom V.