The literature that comes with the Holley Secondary spring kit has entries for 350 cu in and 402 cu in vehicles. If I scale the information for my 230 cu in Slant six. I get this:

RPM to Open RPM at full Open
Yellow (Short Spring) 2105 7342
Yellow 2131 7435
Purple 2457 9027
Plain (Std.) 2886 10492
Brown 3472 11288
Black 3482 Never fully opens

Do these these numbers bear out in the real world?
If so, for a daily driver maybe a Purple or yellow would be better than the "As-Shipped" Plain spring. IIRC D.Idiot uses a Purple spring.

bwhitejr

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'72 Duster (Performance 360)
'83 Ramcharger (Performance 318)
'80 TrailDuster (360)
'80 D-150 Truck (See Below)
CompCams 252S, Holley 390cfm, Offy manifold
Ported, Polished and Gasket Matched
P4286813 Springs,0.040 Overbore,
0.090 Shaved Head

I would go lighter until you get a bog and then back off one size bigger than the one that produced the bog. I played around with Holley carbs on both my slant and my 360.

Sam

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BWhite,

I set secondary with black in, then tuned through spring set and found the purple works great for me with a 90 Holley. Of course, t his is on a well "built" slant on an 727 on a truck with a 3.91 and 28 inch tires...

But, yellow was also pretty good.

rock
'64d100

I use the purple spring for daily driving in my 390... I back down to the long yellow spring if dialing up for draggin'... and have used only the brown spring when dialing in my 'modified' Holley 600 cfm...

If dialing in for a truck, heavier might be better since the load on the engine is a bit greater (load factor)...

-d.Idiot