V8 conversions: Torsion bar size and rear spring rates?, What do you run? Options

[tygaboy]

Hi V8 folks -
I'm looking for recommendations to size my torsion bars and rear spring rates.

Component-wise, it's an LS3 with Boxster 6-speed. The total drive train weight is around 575 lbs.

I'm running Koni yellows (helper springs on the rear), 17mm raised front spindles and the 2" Tangerine rear suspension points and tall shock tower kit.

I'd like the ride to be sporty but tolerable. if that means anything! The use case is "spirited street driving" I'm not worried about ultimate track performance - at least not yet.

So, wha'cha running?
Thanks,
Chris

[roblav1]

On my performance based build, I have 21mm Sway Away bars on the front. Have not driven yet but bounce feels about right for performance street.
Rear springs are aftermarket blue... no idea of make or rate but feels around 250 lb per inch. I don't like those rear springs because they go loose at full rebound droop extension at a ride height that isn't low enough for what I want. The rear spring rste feels about right though. I may take them out and measure the rate in a drill press.

I'm thinking the rear coils should be progressive rate to prevent looseness at full droop.

On edit, my rear setup is exact same as Valco Oscar except springs are blue. The real solution is shorter rear dampers.

[tygaboy]

On my performance based build, I have 21mm Sway Away bars on the front. Have not driven yet but bounce feels about right for performance street.
Rear springs are aftermarket blue... no idea of make or rate but feels around 250 lb per inch. I don't like those rear springs because they go loose at full rebound droop extension at a ride height that isn't low enough for what I want. The rear spring rste feels about right though. I may take them out and measure the rate in a drill press.

I'm thinking the rear coils should be progressive rate to prevent looseness at full droop.

On edit, my rear setup is exact same as Valco Oscar except springs are blue. The real solution is shorter rear dampers.

@roblav1 - You can solve for the "loose spring at full droop" via adjustable coil overs with helper springs. I got this set up from Elephant Racing. Works like a charm.
The helper springs (the flat coil spring at the bottom) fully compress as soon as the car is set on the ground but keep the spring seated at full droop.