Annular Boosters VS Downleg Boosters Which Is Better? | Holley Carb Secrets Tips And Tricks
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- Опубликовано: 5 июл 2024
- Today we are looking at the differences between the standard straight leg booster that you see in the basic holley carburetors and the more modern down leg boosters with the even more modern annular boosters. Straight leg boosters work and have have worked for over half a century, there are no real downfalls of the straight leg booster. The downleg booster is just an updated version of the straight leg. The down leg booster moves the fuel outlet much lower in the venturi, allowing the signal to the carburetor to be much better and respond faster. The newest booster design is the annular booster. Despite its size, it seems to be the preferred booster for high performance applications but the main draw back of the annular booster would be its size that limits airflow and its cost. In this video I will be going through all of this so sit back, relax and enjoy the show.
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Keep it hard dude youre one of the best carb tuners l have had the pleassure to listen to
I appreciate it man, it means a lot 👍
I remember when my mother bought an 82 Cadillac Sedan Deville with the 4100 v8. It was our first fuel injected car. My father called it a wire carburetor. I used to take the air filter lid off and stare at the fuel being injected into the engine.
I used to do the same thing with my dads 85 ramcharger when I was a kid 😂
Ecellent. Thank you for that...well done sir.
Thank you! I appreciate it!
One of my all-time favorite carbs is 9381 (830 annular) used to buy them new for $379 for ever then the prices just crept up. That carb worked good on a built small block or a moderate big block. Recently had trouble with a 9379 (750 annular) on a 383 with vic jr that had an off idle hesitation that just didnt improve satisfactorily no matter what I tried, then I just swapped everything onto a 4779-6 mainbody and the issue was resolved. It seemed like the engine liked having the booster closer to the venturi and gave much better response. That was the first time I had an engine combo that was happier with the downleg booster vs the annular.
id love to learn how to fit annulars to a carb.. that and where do you get them?
Several companies sell them in different styles. Dambest and BLP off the top of my head but the tool to actually install them is expensive. Also, a lot of custom carb builders can install them for you, cheaper than it would be to buy everything yourself. PRC carbs is one of those guys
There is a rule of thumbs with boosters. Most active booster is the annular. It will atomize fuel the best and start drawing through the mains a little sooner too compared to straight leg... Less active and dont atomize as well.
Annular=small particles
Straight=large particles
Large particles of fuel work better on a factory/heated type intake manifold
Small particles doesnt need as much heat on the manifold
There is a "optimal droplet size" you just have to pay attention what works best on your setup. But thats about where my knowledge ends as of now... Pretty much you could end up using the wrong booster chasing power over-atomizing the mix (on a heated manifold more commonly)
Its all a balance for sure. A lot of edelbrocks run annular boosters standard. I've also heard guys say they they tend to run richer on the top end as well, kind of like a siphon. All 3 of my blow through carbs are down leg but maybe on my next one, I'll build annular booster carb 👍
Well, that's what the books say.
Annular boosters. Make sure everything is clean. I’ve repaired performance cars where one or more of the fuel delivery holes in the boosters. That sucks. And you can’t compare each of those with actually flowing them. Then run a Dino sheet. This is basic.
Will a 750 proform main body fit on a 750 demon carb?? I was thinking of changing out to a proform annular main body if it works.
Yes it will. Just make sure you get the right one(Mechanical secondaries or vaccum secondaries). If the idle holes dont line up, I have a video about that. Its not a big deal
@@NightWrencher awesome, thanks! I'll look for the video and watch as a heads up.
@@jeremymyers5643 I think it was a video directly before or after this one
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It's not recommended to use a carburetor with straight leg boosters on an intake manifold that is un-heated.
Most off the shelf carbs are straight leg boosters unfortunately. If you want something with downleg, you're gonna have to pay a premium. I wouldn't say theyre "not recommended" but if you have the option to go downleg or better yet annular, I'd definately jump on that instead.
Only way to know is to test them on different engines.
Somebodys gotta do it, and its probably gonna be me 👍
@@NightWrencher I've been rebuilding carbs for a good 30 years.
All sorts of applications. Racing, street rod, economy etc.
Have a large collection. More curious if changing boosters will increase miles per gallon. I'll get around to it once I get the right carb to test.
This summer I'm going to run an engine on the dyno and do some testing.
I'll have to find that right carb.
It should, anything that increases horsepower without adding fuel should be better for MPG. People claim annular boosters take less fuel to make the same horsepower so thats where I would start 👍