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Discussion Starter #1 (Edited)
have a 6619-1 holley carb on my 69 z28 with a 350 cu in in it.
want to change secondary spring. has orig black in it now.
engine , I think, has a small cam in it. what spring should i
put in the carb? is this a big job,as I never did it before ?
runs good with this carb. thanks.
 

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Not sure if the spring you have is stock or not , but Holley has a spring assortment that you can select from , weaker to stronger.
I think this carb is from the 1850 series, single inlet, banjo fitting and fuel balance tube to rear bowls. Not a hard job to change, some times you have to remove the entire diaphragm to do this or get to the last screw near the choke, if it has one.
Any local performance shops in your area?
 

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What is happening to make you want to change secondary spring. Here is a little info about 0-6619-1 from Team Chevelle forum. The Holley 0-6619-1 is an early 1970's emmissions aftermarket replacement carb. It is a 4160 series that flows approx 600 CFM.These carbs have a fairly lean idle circuit and a relitivly large PVCR (Power valve channle restrictor) that allowed decient power.As assembled from Holley these carbs had a Black secondary diaphram spring. The Black spring is the heaviest spring made and designed to not allow the secondaries to open fully. Changing springs is necessary to allow full secondary opening.

These carbs were never intended as performance carbs.Their idle circuits were designed lean to be easy on emmissions and as such they dont respond well to big camshafts.These carbs ( there were several of this family of carbs 0-6619,0-6909,0-6919 ect ect ) were discontinued several years ago. Here is an article on changing and adjusting the secondary spring. https://www.holley.com/products/fue...components/vacuum_secondary_parts/parts/20-13. Finish tuning as normal adjust floats, jets, poer valves, etc.
 

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Discussion Starter #5
Car is orig x77 z 28, 4 speed, 3:73posi. 74 k miles. Bought from orig
Owner. It is orig color burgundy with white stripes. Pretty nice shape.
Orig owner blew engine drag racing, so he installed this 350 with a
Slight cam. The Holley carb's sec spring is black and I want to change
To a lighter spring to open secs as the black won' t open all way.
Thanks for all your info. I will buy a spring kit. Jerry
 

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Testing springs is easy.
Put the black spring onto a rod or pencil and take a selected spring and put it onto the rod small coil end to small coil end.
Now compress the large coil end of the springs by hand- the spring collapsing first is the weaker spring.

You may not know any difference performance wise as the secondaries open on demand or as needed.

Another trick is once the diaphram is off the body, pull out the lead slug and drill the hole to 0.089" this opens up the orifice to the venturi allowing a bigger pipeline for the pressure change in pulling open the secondaries.
Some people remove the check ball in the secondary housing.
 

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Go to Holley's site and view the spring performance chart. Figure out what spring you want to experiment with and buy that one or just get the kit that has them all and includes the spring performance chart.
 

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Go to Holley's site and view the spring performance chart. Figure out what spring you want to experiment with and buy that one or just get the kit that has them all and includes the spring performance chart.
Perfect advice.
 

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What is the issue u are trying to fix?
Rem if u can feel the secondaries come in . they are not adjusted correct.
And as Everett mentions "
You may not know any difference performance wise as the secondaries open on demand or as needed."
Which means about the only difference u would see is if u had a O2 data logger on the car and extreme fine tune AFRs in a WoT rich situation where there is rather a huge tolerance between 11.5 and 12.5 AFR anyway. and any 'feel' will just mean the spring is so way wrong the secondaries are working wrong
 

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What is the issue u are trying to fix?
Rem if u can feel the secondaries come in . they are not adjusted correct.
And as Everett mentions "
You may not know any difference performance wise as the secondaries open on demand or as needed."
Which means about the only difference u would see is if u had a O2 data logger on the car and extreme fine tune AFRs in a WoT rich situation where there is rather a huge tolerance between 11.5 and 12.5 AFR anyway. and any 'feel' will just mean the spring is so way wrong the secondaries are working wrong
Steps, are you saying that if the carb is wrong, it'll feel just like it's right?:rolleyes: Or vice-versa?:D:
 

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Go to my web site, Holley section and look at the spring chart at what RPM the springs start to open and when they are fully open and figure which one suits your engine.
Vacuum secondaries don't open based on engine rpm's, they open when the level of ported manifold vacuum increases enough to overcome the spring pressure.
 

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Steps, are you saying that if the carb is wrong, it'll feel just like it's right? Or vice-versa?:
No I cant say that because I have no idea how or what the car is used for or what the final diff ratios are....
Read the 2 posts above , get the original spring for tha carb for that application or close to it
 

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Vacuum secondaries don't open based on engine rpm's, they open when the level of ported manifold vacuum increases enough to overcome the spring pressure.
Nope. Manifold vacuum has nothing to do with the opening of the secondaries, and essentially goes to zero when you go to WOT. Venturi vacuum, generated in the primary venturi by increasing air velocity past a fixed orifice pickup (Bernoulli's Principle) feeds the secondary diaphragm chamber, and is augmented by another fixed orifice pickup in the secondary venturi when they begin to open. :thumbsup:

:beers:
 
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