I started my thirdgen journey as many others: a desire for performance. To that end I modded my original LG4 until it was at least the equivalent of an L69, and when retirement rolled around, I threw in a 350 HO Deluxe mated with a GM lightweight flywheel (16 pounds) and an aluminum drive shaft. Did the combo live up to my expectations? You danged betcha! But...Yeah, there's always a "but." I grew to loathe engaging the clutch from a standstill, I grew to loath the lag between shifts. So? So recently I had a clutch kit installed and I replaced the lightweight flywheel with a standard 24 pounder. The result? I have a new car, one that takes off from a stop without fuss, one that shifts so smoothly that I find myself grinning like an idiot. In my seventh decade, I'm seeking drivability, which is why I tossed the Astro Van steering shaft (the noise was awful), replaced the poly trans mount (something designed for teeth-rattling vibration in the lowest regions of hell), why I set the Koni Yellows on full soft, why I...well you get the idea. My younger self was willing to ignore the price of performance; my weary older self just desires drivability. Do I regret my journey? Not a whit.

JamesC

 

If you're indeed running 3.23 rear gears, it makes good sense heavier flywheel inertia would add to better drivability.

I am of the camp that happily matched gearing is a major factor in a vehicle being a slug, or being enjoyable to drive. Trans. gearing and flywheel weight are major components of all that.

I tolerated a set of not-so-round tires 20 years ago. That's another component of learning that NVH nded not be confused with performance.

 

Did the 89 IROC 5 speed use the heavy or light flywheel?

 

I too considered a lightweight flywheel for my GTA when I was building it. I'm glad that in the end I decided against it.

I was considering a lightweight aluminum at 13lbs. I'm glad I didn't in the end, I would have hated the car tremendously on the street no matter how much fun it would have been on the road course.

 

I personally like an extremely lightweight Fly-Wheel in a Drag-Race only vehicle...
However I absolutely hate it, for street driving.

Forget "Stop and Go" traffic.


I have the most experience (using an extremely lightweight Fly-Wheel) with a Spec brand multi-disc Clutch-System, that included the Fly-Wheel.
This was used in a 3,200 Lbs Third-Gen, with an extremely modified T56 (originally from an SSR-Truck) and the usual modified Fourth-Gen Hydraulics.
This set-up worked well on both Slicks, and the now more popular "Drag-Radials".

 

@JamesC

So where did you find a heavier flywheel? I am putting a mostly stock 350 in my 88 and all I can find are the 16-20 pound wheels. I'd love to find a 24 pound that isn't crazy expensive but if I have to pony up, I will.

 

Here's what I purchased:

https://www.jegs.com/i/JEGS/555/601257/10002/-1

JamesC

 

Thank you! I wonder if that is the smart choice for a 3.45 gear car and aluminum driveshaft. I bought the car non-running so I don't really know how driving it with the 16 pounder was.