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Do Holley carburetors always need adjusting?



Do Holley carburetors always need adjusting?

This one has always puzzled me. Almost every muscle car came from the factory with a Holley carburetor or multiple Holley carbs on it. That includes many of the Shelby's, Cobra's, Tri-Power Vettes, some of the big block Chevelles, Six Pack Mopars, Dual 4 Mopars, Ford "6V" systems, first and second generation Z/28's, and even motor homes, trucks and commercial delivery vehicles came with factory installed Holley carburetors on them and none of them ever have, or had, any problems. Many of these cars and trucks are still running today, so it would seem funny that Holley's got this bad reputation of always going out of adjustment or needing to be tuned all of the time. That is SO far out in left field, it isn't even funny. This image shows an original Shelby GT-500 with it's original pair of Holleys on it. Holleys need no more tuning or adjusting than any other carburetor. The #1 issue with ANY carburetor and why they have problems is... dirt, either in the needle and seat, which causes flooding, or in the fuel circuits which cause idling and running issues. Keep dirt out of your carb and you shouldn't have any problems with it, whether it's a Holley or not. It's really that simple. 

Do Holley carbs always need adjusting?

I've always chosen Holley carbs for most of the performance and race engines I've built because they work! Ask yourself this: what did you see on all NASCAR engines before they went to fuel injection? What did you see on Pro-Stocker's? What do you see on the new Shelby Cobra's from Shelby America? ALL Holleys! GM, Ford AND Chrysler, AND Shelby, AND NASCAR, and all of the million other performance engine and car builder's out there aren't stupid. Ever see a NASCAR have to come into the pits because the carb needed re-adjusting? This image shows a typical NASCAR engine by legend, Robert Yates, with a Holley carburetor on it back when they ran carburetors.

Do Holleys always need adjusting?

 

 

Here's a 427 Tri Power Vette engine with guess what? Holleys on it.

Do Holley carbs always need adjusting?

 

 

And here's Dodge's version of a 6 pack, with 3 Holleys.

Do Holley Carbs Always Need Adjusting?

 

And even the Ford six pack set-ups, called "6-V" for 6 "venturis" came with 3 Holleys on them.

Do Holleys always need adjusting?

 

 

 

And here's the mighty 426 Hemi with two Holleys on it.

Do Holleys always need adjusting?

 

 

 

And here's one on a 69 "DZ" 302 Z/28. They all came from the factory with these. Even the ones with the super rare cross rams had 2 Holley's on them and ran great for years. 

 

Do Holley Carbs Always Need Adjusting?

 

And here's the first original "780" vacuum secondary that came factory installed on 396 Chevelles. 

Do Holley Carbs Always Need Adjusting?

Shelby's and Cobras also came equipped with Holleys on them. Here's an old barn find 68 Shelby GT500 428 Cobra Jet with the factory dual 4 Holleys on it.

I think you're getting the picture that a LOT of factory muscle cars (and other vehicles as well) came with Holley carbs on them that didn't "always need adjusting". 

Do Holleys always need adjusting?

So what about other carburetors such as an Edelbrock? I was friend's with the entire Edelbrock clan, not to mention I was Edelbrock's official installation video host and ambassador and I can tell you first hand that Vic himself would tell you that for a serious performance engine, you need a Holley. He wasn't about pulling the wool over people's eyes and have you buy one of his carbs for your nasty engine and then not have it run as strong as it could. Sure, an Edelbrock (AFB) carb will run nice, but not AS nice as it could with a Holley on it if it's a more serious engine.

Vic Edelbrock and his brand and company were always all about quality and happy customer's. A customer with a carb that just can't cut-it isn't a good sale for the next items he (or she) may need for their ride, not to mention, Edelbrock caters to the masses who have milder engines and cars, not the small group of people who have wild engines in serious performance cars . Again, don't get me wrong, there's nothing wrong with an Edelbrock carb which is a re-make of a Carter AFB that is actually made by Weber, hence the WEBER name on the side of Edelbrock carbs and the "W" markings all over them. For a stock or basic mild performance engine, an Edelbrock carb is just fine. You won't see them on NASCAR engines, Pro-Stock engines, etc though, and for good reason.

holley carbs

I always preferred Holleys, or Holley design type carburetors such as Quick Fuel Technology like you see in the picture, and none of them ever needed constant adjusting, just like none of the original muscle cars that came with Holleys ever needed "constant" adjusting. ALL of the needle and seats in all of them work similarly, and all of the floats work similarly, and so on. In fact, carbs like the Quadrajet, Edelbrock (Carter AFB types) and so on are actually much more complicated in design than any Holley is because Holley's don't use things like metering rods and jet combinations, and they don't need to be fully disassembled to change things like the needles and seats or the accelerator pumps. It's exactly why race teams and serious cars use them instead of other types of carbs. 

The main issue with Holleys having problems is dirt! But this is true for ANY type, or brand of carb. 99% of the time, the problem guys have with their Holleys is simply dirt in the needle and seat which prevents it from seating properly to shut-off the fuel supply going into the bowl, so what happens is; gas over fills the bowl which causes it to gurgle-up through the vent tube and run down the throat of the carb causing it to flood and run terrible. That's not the carb's fault. It only takes a tiny little particle of dirt to cause that needle and seat to not shut-off, so as the engine is running, fuel flows into the bowl faster than the engine can use it, (most commonly when it's idling), because that needle and seat isn't completely shutting off and it causes flooding which in turn causes it to run terrible. But again, it's not the carb's fault. Most other brands and types of carbs use VERY similar types of needles and seats and they don't need additional adjusting anymore than any Holley does.

Do Holley Carbs Always Need Adjusting?

One thing Holley carbs have that many others don't is a power valve, which is basically just a vacuum operated "enrichment" valve that allows more fuel to feed your engine while accelerating. These valves, or "diaphragms" can pop if you backfire or spit through the intake manifold and carburetor, like when the engine is cold and is too lean.

When a power valve pops, it allows fuel to leak down the inside throat of the carb which makes it way too rich to sustain an idle. A common sign of a popped power valve is when your engine won''t idle but it runs down the road and accelerates just fine. This is because when you're running down the road or are accelerating, your engine needs and uses a lot more fuel than it does at an idle, so it can burn the excessive fuel leaking down the throat, were at an idle it simply can't. 

If your power valve pops, it's not the power valve's fault that your engine isn't tuned right which causes it to cough or spit (backfire back up through the carb) wen it's cold or when nailing the throttle because it's too lean. That's your engine's fault, but somehow Holley carbs get the blame for it. To remedy this issue, make sure you don't try to drive when your engine is cold because a cold engine requires more fuel than a warm engine does, and if it's cold, then it's lean which can cause it to spit back-up and pop your power valve. That's one of the main causes for power valves to pop and cause flooding and bad idling issues.

Do Holley Carbs Always Need Adjusting?

Now, since the late 90s or early 2000s, Holley has been installing power valve savers in their carbs which is basically a simple check ball installed on the underside of the base plate that slams shut and prevents pressure caused by the lean backfire to get inside the carb and pop your power valve. Older Holleys didn't have these which made them prone to popping them if your engine was prone to spitting and coughing.

Do Holley Carbs Always Need Adjusting?

If you have an older Holley carb, you can buy a Power Valve Saver kit from Holley and install it yourself. It's a simple drill bit and check ball, and they only cost a few dollars. The little orifice where it goes is already there so all you need to do is drill it out with their supplied drill bit to make it the right size and then tap-in the little check valve and you're done. It's actually a pretty simple thing to install and it "can" save you from popping a power valve. I say "can" because they aren't 100% fail safe every single time, but they do cut way down on the chances of your power valve getting popped if your engine spits or coughs. I say they are totally worth it and I always installed them on older Holleys that I was either rebuilding or customizing. 

Hey, if you liked this tech tip then please be sure to share it with your fellow gear head friends, and on your favorite car forums by copying the URL at the top of the page and sharing it with them. Thanks! 

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