Auto or manual?   looks like you might have a truck..?  I have found a sedan with auto Ive settled on a slightly heavier spring , brown when I was running both Holley 450 and a 600 cfm

Oh and by the way, don't be frightened to go up  a few jet sizes if needed [ask Rick55 ]



"Came too close to dying to stop living now!"

I've had no trouble with the sprint that came in my Summit 600. I will add that the DVD that comes with it is a waste of time. Go on YouTube and search for Summit. Alot more information about tuning their carbs there.

Durham Missouri

Thanks so much Ted, is that a y-block in your roadster?

Always start off with the secondary spring that comes with the carburetor.  Second guessing the Holley engineers by changing out the supplied spring before even running it will simply make for more work.  As mentioned, if you feel the secondaries coming in, you likely have too weak a spring.  The secondary opening transition is expected to be smooth and un-noticeable other than the hard pull of the engine.
 
As a general rule, the factory supplied silver spring is a good starting point for most Holley 4V vacuum secondary carbs.  This even applies to the Holley model 2140/4000 Teapot carbs which uses the same springs as the model 4150/4160 vacuum secondary carbs.  Dual quad setups will start off with the long yellow spring which is basically half the tension of the silver springs.  This is due to the air flow through each carb on a dual quad setup essentially being cut in half which is compensated for by using secondary springs with reduced tension.  The secondary spring on the single four barrel Holley on my roadster is the ‘black’ spring which is the stiffest one available.  The carburetor signal at low rpm is very strong on that engine and requires a stiffer spring to slow down the secondary opening.

Lorena, Texas (South of Waco)

No one can tell you what your combo needs.  You have to tune it yourself.  The summit carbs come with DVD instructions.  I would imagine it covers secondary spring tuning.  If it does not cover that, here is a link to Holley's instructions for street avenger carburetors.  Look at the secondary tuning section.  http://documents.holley.com/199r10219-3rev5.pdf


Lawrenceville, GA

The usual advice from Holley - is to make sure the opening point is almost undetectable. I usually start with the "black" spring (stiffest) and work BACK from there.  

 
 Steve Metzger       Tucson, Arizona

Howdy all. I am curious as to what experience any of you have had with holley secondary spring choices. I have a 292 bored .030 with mummerty aluminum intake and headers, and isky e4 cam 9 the milder one ). I have a summit 600 cfm carb. I bought the quick change secondary spring housing and am beginning to play with spring options. Would my set up like a softer or stiffer spring? I have the white ( softest spring ) in now and it feels pretty good. Secondaries are for sure opening. I'm curious what experience you guys have had with a similar engine set up. Thanks