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Old 06-13-2010, 03:08 PM
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Quickfuels screw adjust holley secondaries

Has anybody tried the Holley adjustable vacuum secondary mod from Quick fuel? Did you like it?

Never been a fan of the holley vacuum pod. Stock spring/vac pod doesn't want to open secondary blades up all the way. Most of the time getting 650cfm from a 750.

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Old 06-13-2010, 03:32 PM
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I have used two different versions of the same idea in the past. One I know wasn't Quick Fuel(can't remember the brand) but it worked the same, and it worked great to fine tune things once you got the correct spring determined. I don't think it will have enough adjustment if you are going to try to adjust it using only the stock silver spring that most Holleys are equipped with.

The other adjustable housing I used had a screw adjuster through the top of the vacuum pod, you used it to decrease or increase spring pressure. You also have to test with this set-up and decide on the correct spring for the application, then use the adjustment for fine tuning.

I don't think any of the adjustable cans are a shortcut to avoid having to buy the spring assortment and testing springs on the engine, just a way to even more fine tune it.

VS carbs rock, even at the Drags, if you learn how to work with them.
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Old 06-13-2010, 03:58 PM
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Originally Posted by spinn
Never been a fan of the holley vacuum pod. Stock spring/vac pod doesn't want to open secondary blades up all the way. Most of the time getting 650cfm from a 750.
Personally, I prefer DP Holley carbs.

If you use the tricks, you can make a VS Holley perform as good as it can- but it will never be a DP. But then some guys just don't want or need the "immediacy" of a DP on the street.

A couple things I've learned:

Don't cut the VS springs shorter- this will not help matters. Instead, use a softer spring.

Removing the vacuum secondary diaphragm housing check ball entirely is not something you should do. If you take a modified small phillips head screwdriver (all it has is carefully sharpened blades) and use it to "dimple" the check ball seat located in the vacuum housing, you can get a quicker response of the secondaries despite what spring is in it. Or you can deepen the groove that's already there on some carbs. I've also used aluminum check balls in the past to provide quicker activation.

Newer carbs have a brass restriction (no ball) and have to be carefully enlarged to gain the same advantage- but a numbered drill bit set and a pin vise is needed (which you should have for carb work, anyway).

The biggest hurdle to getting good response out of a VS carb is the lack of a secondary accelerator pump. If you go too quick w/the secondary activation, it WILL bog. There are mods that can be made (shooter, cam, and delivery) that alleviate this to some extent, but the best cure for this is a DP carb.
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Old 06-13-2010, 04:42 PM
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I have a proform vacuum secondary carb which has the same exact same adjustable housing that your talking ( quickfuel guys make proform carbs as well) about and they really work nice on my supped out 350 sbc. I have yet to adjust it to where it will bog then back it off some but I have it good right now to where I get excellent throttle transition with no issues. All you have to do is turn the screw for the spring tension. I have yet to take it apart to really see how it works but it does work good.
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