another Carb question

[SS Shaun]

So i am finally getting on my chevelle and having fun with it. So now that i have correct fuel pressure, and the bowls are set and accelerator pump is set no more carb poofs its awesome. So now i am getting on it and opening those vacuum secondaries but here is my question/problem. When i step on it and the secondaries open up i get like a space or a flat spot when those open it up. No miss fire or anything, it seems like it has to catch its breathe and then go. Its like a split second. So a friend of mine helped me install a spring kit setup.

on that spring kit i have a huge amount of springs with colors on it. I put the black spring back in it. So what should i do? Put a different spring in its place? How do i know what spring to use? Do i need a weaker spring or a stiffer spring? trying to learn and figure it out too :) btw Holley 750 dual feed carb

[chevymaher]

It is bogging because it is opening to fast. Use a weaker spring. Just keep trying different ones till you find her sweet spot.
I just put a screw in the slider and hammer it open. When it comes off the bog it all business. Or just roll into it as the engine likes for normal playing.

[SS Shaun]

i have to double check which spring i have in mine now

[chevymaher]

I said weaker it should be stronger spring to fight the vacuum. I just brainlocked because i like them to open fast.

[mestorod70]

The black spring is the heaviest and will delay the most.
Here is the order of the spring tension.
Black...brown...plain no color std spring...purple...yellow....and short yellow.
Displacement effects opening rate...biger engine earlier open.
When tuning you should not feel the secondary open...smooth is a faster car.
I would try the purple spring and see.

[SS Shaun]

you nailed it. I put in the purple spring and it was pretty much on point!!

[Hank70SS]

I said weaker it should be stronger spring to fight the vacuum. I just brainlocked because i like them to open fast.

The black spring is the heaviest and will delay the most.
Here is the order of the spring tension.
Black...brown...plain no color std spring...purple...yellow....and short yellow.
Displacement effects opening rate...biger engine earlier open.
When tuning you should not feel the secondary open...smooth is a faster car.
I would try the purple spring and see.

You both said heavier spring but as Shaun found out it was the lighter spring. It is confusing but a lighter spring as metorod70 suggested will delay the opening as the vacuum has to drop lower before the spring wins out over vacuum. In a heavy car like a Chevelle you need to delay the opening some, the engine needs a moment before it can handle the extra air fuel mixture from the secondaries. Check out the Holley manuals on tuning their carbs, it's explained in there.

[chevymaher]

Yea I do this stuff and reason it out. Then once the job is done the information is put some where else in my head. Carbs are getting more rare and I don't deal with them every day like I used to. Fuel Injection issues are what are coming to work now.

I got my work frame of mind and my home frame. I have people ask remember you did this to my car. I don't remember until my memory is refreshed. Once I finish a job it is gone, on to the next adventure.

[mestorod70]

Carb secondary spring chart in the 1985 holley parts book

[SS Shaun]

when i was doing a little research i found this chart
http://www.nastyz28.com/~copo/images/sec%20spring%20color%20350.jpg

and this one

http://www.nastyz28.com/~copo/images/sec%20spring%20color%20402.jpg

but as of right now the purple spring seems to do the job right now. no gasp for air just nice and steady. I checked my uncles 350 and he also has the purple spring in place so i guess it does the right thing for the way we drive (really the way i drive my uncle drives like a whimp)...lol

[SS Shaun]

finally got to take the chevelle out and really get on it. Man what a difference with correct spring in the carb. It ran leaner because it was really rich before. Now it feels like i have power now that its not super rich. Timing seems to be on point, only thing i need to adjust is the idle seems to be a little high its about 1000-1100 rpms. but its running so good i didn't want to park it...lol