Annular Booster vs. Down Leg boosters, what works best...
06-01-2005, 06:11 PM
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Annular Booster vs. Down Leg boosters, what works best...
Anyone out there have any comparisons between the annulars and regular down leg boosters for their Holley or Demon carbs? I have always thought the Annulars reduce cfm through the carb at WOT, but improve the low speed and mid range response and power.
I called a Holley tech guy today and he told me the annular boosters improve the high speed flow of the carb, which makes no sense to me. What do you guys think?
I called a Holley tech guy today and he told me the annular boosters improve the high speed flow of the carb, which makes no sense to me. What do you guys think?
06-01-2005, 08:10 PM
#2
Race Director
I tried them both can't tell the difference between the two, most likely the onlly time you would see any difference would be 1/4 mile times others more knowlegeable on this subject will add somethng I hope I could not figure it out 
06-01-2005, 08:11 PM
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I tried them both can't tell the difference between the two, most likely the onlly time you would see any difference would be 1/4 mile times others more knowlegeable on this subject will add somethng I hope I could not figure it out, as a matter of fact I am not even sure what boosters my new Race Demon has
06-01-2005, 11:15 PM
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Of course the correct answer is "it depends"!!
Generally the annular works well at lower speeds and helps atomize fuel better. They were actually developed for bobtail truck stuff to help throttle response.
They also work very well in a set up where you might be using a carb that is "too big". Like when I stuck my 1050 Dominator on my oval port 427. Worked great when I was done tweeking a little.
Also helps with a motor with too big of a cam with lower vacuum. Fuel flow starts a little earlier with them.
All that said, they do tend to go rich at extreme high rpm. All that increased booster signal and multiple holes allow more fuel in when RPM goes high and vacuum is high.
They also cut airflow because they are bigger.
The downlegs are a nice compromise. They are deeper into the bore and will start fuel flow earlier than straight ones. Since they are down in the bore, they cut airflow too.
But all that airflow cutting is relative on most carbs unless you have something extreme. Extreme would be a dyno test I witnessed where a Busch type roundy pounder was being tested with a pile of different 390 cfm Holleys from various builders. There was a pretty wide range of power, but there was one that was illegal. All that had been done was that the boosters had been trimmed "thinner" (top to bottom) by about .075". That sucker was up 40 HP over the others! In that little tiny bore at those rpms, .075" was a lot! Of course that's why they were caught cheating too!
Just for reference, I'm still using the same 1050 annular on my 540. I have huge heads, a huge intake and it still has fine driveability. I think the annular really helps. But it does get fat at the top end. Some airbleed work can cure that though.
JIM
Generally the annular works well at lower speeds and helps atomize fuel better. They were actually developed for bobtail truck stuff to help throttle response.
They also work very well in a set up where you might be using a carb that is "too big". Like when I stuck my 1050 Dominator on my oval port 427. Worked great when I was done tweeking a little.
Also helps with a motor with too big of a cam with lower vacuum. Fuel flow starts a little earlier with them.
All that said, they do tend to go rich at extreme high rpm. All that increased booster signal and multiple holes allow more fuel in when RPM goes high and vacuum is high.
They also cut airflow because they are bigger.
The downlegs are a nice compromise. They are deeper into the bore and will start fuel flow earlier than straight ones. Since they are down in the bore, they cut airflow too.
But all that airflow cutting is relative on most carbs unless you have something extreme. Extreme would be a dyno test I witnessed where a Busch type roundy pounder was being tested with a pile of different 390 cfm Holleys from various builders. There was a pretty wide range of power, but there was one that was illegal. All that had been done was that the boosters had been trimmed "thinner" (top to bottom) by about .075". That sucker was up 40 HP over the others! In that little tiny bore at those rpms, .075" was a lot! Of course that's why they were caught cheating too!
Just for reference, I'm still using the same 1050 annular on my 540. I have huge heads, a huge intake and it still has fine driveability. I think the annular really helps. But it does get fat at the top end. Some airbleed work can cure that though.
JIM
06-02-2005, 12:35 AM
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Jim,
As usual, thanks for the detailed reply. I am thinking of a carb (HP Series 830 dp) with annulars to help offset the square port heads I am running. My set up is not quite as strong on the bottom as I think it should be. Part could be my current carb is a little lean. I messed with the IFR's and idle air bleeds back when the carb (Silverclaw-very similar to the Mighty Demon) was on a very mild 427.
But it sounds like the Holley guy was mistaken about carbs with annulars being better on the top end, I guess the engine builders get the experienced tech guys when they call!
Great insight on the dyno test. 40 hp for .075" difference. Wow.
Wish I could have made the trip to BG this year. Glad to see yours ran well. I have a few issues keeping my roadtrips short. Main one is a vibration around 2500 rpm. I have narrowed it down to the clutch (Centerforce DF). Hate to pull it, but that is the next step. McLeod single disc a good choice for 525-550 hp?
As usual, thanks for the detailed reply. I am thinking of a carb (HP Series 830 dp) with annulars to help offset the square port heads I am running. My set up is not quite as strong on the bottom as I think it should be. Part could be my current carb is a little lean. I messed with the IFR's and idle air bleeds back when the carb (Silverclaw-very similar to the Mighty Demon) was on a very mild 427.
But it sounds like the Holley guy was mistaken about carbs with annulars being better on the top end, I guess the engine builders get the experienced tech guys when they call!
Great insight on the dyno test. 40 hp for .075" difference. Wow.
Wish I could have made the trip to BG this year. Glad to see yours ran well. I have a few issues keeping my roadtrips short. Main one is a vibration around 2500 rpm. I have narrowed it down to the clutch (Centerforce DF). Hate to pull it, but that is the next step. McLeod single disc a good choice for 525-550 hp?
06-02-2005, 08:23 AM
#6
Team Owner
I'm not sure if I made the right carb choice. I went with the annular booster model because it was more expensive than the downleg booster carb.. Looks like more expensive doesn't automatically mean better...
BTW, I have a Holley 80514 1000 cfm mech. Secondaries double pumper HP series carb with annular boosters... It was $750 at Summit and the downleg version of that carb was about $700...
BTW, I have a Holley 80514 1000 cfm mech. Secondaries double pumper HP series carb with annular boosters... It was $750 at Summit and the downleg version of that carb was about $700...
06-02-2005, 11:31 AM
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Originally Posted by Doug Brandon
I am thinking of a carb (HP Series 830 dp) with annulars
Brett
06-02-2005, 10:49 PM
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Originally Posted by Doug Brandon
Jim,
But it sounds like the Holley guy was mistaken about carbs with annulars being better on the top end, I guess the engine builders get the experienced tech guys when they call!
But it sounds like the Holley guy was mistaken about carbs with annulars being better on the top end, I guess the engine builders get the experienced tech guys when they call!
The annular booster is higher above the venturi and is less responsive to low speed air, but reacts better to high speed air and is less restrictive air flow through the booster and venturii.
Someone said something about the vacuum ports that is correct, but If your engine is a mild 427 I seriously doubt you will need the 830. While it certainly has the CFM for the top end power, you will rarely need it on a street driven engine and a 750 cfm carb might be a better choice. I have not seen the entire combination you are using, but do the math. Plus if you go with the 750, you can use one of our new Street HP carbs that has all the benefits of the HP race carb with all the vacuum ports for the street, a shiny finish and calibrated for street use.
My two cents.
If you need to talk to a good carb guy in Holley Tech ask for Ray.
06-02-2005, 11:09 PM
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Hey Doug....
The 1000 HP (non -annular) really works well on a big street motor like your 496. Nick has one on his mild 540 and it has run great out of the box. He got 18.9 mpg with the Tremec and 3.08s!! A dual plane will love the bigger carb.
He can vouch for the much better performance than the BG POS he had on it before.
Hey Ray...we were there last week...Doug gave us a 3 hour tour. Neat place you work at!
I *think* I agree with all you said.....but my experience has always been that the annulars get pretty fat at high rpm, and I've been playing with them a long time on the dyno, track and street. But I saw the wet flow testing you guys do too. Wish I had that stuff in my garage!
JIM
The 1000 HP (non -annular) really works well on a big street motor like your 496. Nick has one on his mild 540 and it has run great out of the box. He got 18.9 mpg with the Tremec and 3.08s!! A dual plane will love the bigger carb.
He can vouch for the much better performance than the BG POS he had on it before.
Hey Ray...we were there last week...Doug gave us a 3 hour tour. Neat place you work at!
I *think* I agree with all you said.....but my experience has always been that the annulars get pretty fat at high rpm, and I've been playing with them a long time on the dyno, track and street. But I saw the wet flow testing you guys do too. Wish I had that stuff in my garage!
JIM
06-03-2005, 03:44 PM
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Carb stuff
Thanks for the responses. Nice save on the vacuum port issue. I did not realize that.
Good to see a Holley employee chime in. You never know who out there is reading the Forum! I will contact Ray and ask for his suggestions for my current motor, a moderate 496.
For what it's worth, the BG Tech guy says their annulars are better for bottom end. But he admitted that there may not be that noticable of a difference. He also said the carb I have which is advertised as a 750 cfm dp, flows closer to 950 cfm and suggested I tune the one I have. Wonder if the Holley HP Series is similarly underrated?
Good to see a Holley employee chime in. You never know who out there is reading the Forum! I will contact Ray and ask for his suggestions for my current motor, a moderate 496.
For what it's worth, the BG Tech guy says their annulars are better for bottom end. But he admitted that there may not be that noticable of a difference. He also said the carb I have which is advertised as a 750 cfm dp, flows closer to 950 cfm and suggested I tune the one I have. Wonder if the Holley HP Series is similarly underrated?
06-03-2005, 04:04 PM
#13
Safety Car
That LS6 intake is holding you back. Look in the parts section. I saw a ported Victor (might have been a Vic Jr.) for sale with a machined-down carb pad for clearance under a vette hood.
Found it. It's a Vic Jr.:
http://forums.corvetteforum.com/show...05&forum_id=57
Brett
Found it. It's a Vic Jr.:
http://forums.corvetteforum.com/show...05&forum_id=57
Brett
06-03-2005, 05:30 PM
#14
Le Mans Master
Originally Posted by Brettmc
That LS6 intake is holding you back. Look in the parts section. I saw a ported Victor (might have been a Vic Jr.) for sale with a machined-down carb pad for clearance under a vette hood.
Found it. It's a Vic Jr.:
http://forums.corvetteforum.com/show...05&forum_id=57
Brett
Found it. It's a Vic Jr.:
http://forums.corvetteforum.com/show...05&forum_id=57
Brett
There is very little HP loss from it. Especially on a street motor. Remember Victor manifolds are mainly designed for race use. Doug says he doesn't have as much bottom end as he'd like. A Victor manifold would make things even WORSE.
Dep
06-03-2005, 09:01 PM
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St. Jude Donor '11, '16-'17
I asked this very same question before the split. It driven to page 2 so fast, I didn't get anywhere near the meaningful responses in this thread. The split was good.
06-04-2005, 02:02 AM
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Doug is a great guy, I'm sure by the time you were there you realized he is a big proponent of fuel injection.
Not to bash another companies product, but Holley has been building carbs for 100 years. Started with the ford model A and was the first company to make the modular design for the 57 t bird which is the modular design used still today. Its easy to copy a product, just look at what the chinese companies are doing, but they and no one in the us has the experience Holley does when it comes to carbs.
That being said we rate our carbs at what they flow. We have no reason to inflate numbers as it does an injustice to the enthusiast. Our CFM numbers are a Wet flow number. If you were to flow say a 750 carb using a dry method they numbers will show up roughly 50 to a 100 cfm more.
IF you get a chance to talk to Ray I think you will be surprised about what he can tell you about Holley carbs. I can't recall the number of years, but I believe he has been a holley tech on carbs for over 20 years so he has seen and heard it all.
Not to bash another companies product, but Holley has been building carbs for 100 years. Started with the ford model A and was the first company to make the modular design for the 57 t bird which is the modular design used still today. Its easy to copy a product, just look at what the chinese companies are doing, but they and no one in the us has the experience Holley does when it comes to carbs.
That being said we rate our carbs at what they flow. We have no reason to inflate numbers as it does an injustice to the enthusiast. Our CFM numbers are a Wet flow number. If you were to flow say a 750 carb using a dry method they numbers will show up roughly 50 to a 100 cfm more.
IF you get a chance to talk to Ray I think you will be surprised about what he can tell you about Holley carbs. I can't recall the number of years, but I believe he has been a holley tech on carbs for over 20 years so he has seen and heard it all.
06-05-2005, 12:34 AM
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Doug,
I am the one with the 540 that managed to get 18 mpg last year on the way to Bowling Green. I am very pleased with the Holley HP1000. As someone pointed out earlier, it does not have any vacuum ports. I got around this by drilling and tapping 2 extra holes in my intake. Speaking of intake manifolds, I also ran the LS6 dual plane initially on my 540. When I swapped it for the Holley Strip Dominator single plane that I am running now, I picked up over 30 HP at the wheels. Contrary to conventional wisdom, I did not loose one bit of driveability. I think the big bore and 4.25" stroke has a lot to do with that. I can't promise that you will also see an improvement of 30 HP at the wheels, but I would bet that you couldn't find one bolt on that will give you more HP/dollar on your current combo.
I have run a BG Demon 850 VS in the past and was very unimpressed. Jim let me borrow one of his 850 DP for a while and every aspect of performance improved from driveability to power to efficiency. This convinced me to go for the HP1000 and I picked up 10 rwhp with that change over the 850.
I helped arrange the tour of Holley that Jim mentions above, and one the many things I saw that amazed me was the sheer diversity of carburetors that Holley continues to service. They had a very long aisle filled from floor to ceiling of every type of carb ever built (Holley or otherwise) and they rebuild these for all of the folks selling remanufactured carbs. There is a very sharp group of individuals working at holley on both the carb and EFI side of things. Doug is a great guy and I do enjoy the friendly rivalry that he and Keith have.
I am the one with the 540 that managed to get 18 mpg last year on the way to Bowling Green. I am very pleased with the Holley HP1000. As someone pointed out earlier, it does not have any vacuum ports. I got around this by drilling and tapping 2 extra holes in my intake. Speaking of intake manifolds, I also ran the LS6 dual plane initially on my 540. When I swapped it for the Holley Strip Dominator single plane that I am running now, I picked up over 30 HP at the wheels. Contrary to conventional wisdom, I did not loose one bit of driveability. I think the big bore and 4.25" stroke has a lot to do with that. I can't promise that you will also see an improvement of 30 HP at the wheels, but I would bet that you couldn't find one bolt on that will give you more HP/dollar on your current combo.
I have run a BG Demon 850 VS in the past and was very unimpressed. Jim let me borrow one of his 850 DP for a while and every aspect of performance improved from driveability to power to efficiency. This convinced me to go for the HP1000 and I picked up 10 rwhp with that change over the 850.
I helped arrange the tour of Holley that Jim mentions above, and one the many things I saw that amazed me was the sheer diversity of carburetors that Holley continues to service. They had a very long aisle filled from floor to ceiling of every type of carb ever built (Holley or otherwise) and they rebuild these for all of the folks selling remanufactured carbs. There is a very sharp group of individuals working at holley on both the carb and EFI side of things. Doug is a great guy and I do enjoy the friendly rivalry that he and Keith have.
06-05-2005, 12:52 AM
#18
Le Mans Master
Originally Posted by After Shark
Actually the Holley guy is correct. I should know I work for them. Since downleg boosters are placed further down in the venturii they receive the vacuum signal much quicker, great for low air speed and getting the fuel to pull from the booster, but on the top end they tend to not make as much power because of the way the air has to speed past the booster.
The annular booster is higher above the venturi and is less responsive to low speed air, but reacts better to high speed air and is less restrictive air flow through the booster and venturii.
Someone said something about the vacuum ports that is correct, but If your engine is a mild 427 I seriously doubt you will need the 830. While it certainly has the CFM for the top end power, you will rarely need it on a street driven engine and a 750 cfm carb might be a better choice. I have not seen the entire combination you are using, but do the math. Plus if you go with the 750, you can use one of our new Street HP carbs that has all the benefits of the HP race carb with all the vacuum ports for the street, a shiny finish and calibrated for street use.
My two cents.
If you need to talk to a good carb guy in Holley Tech ask for Ray.
The annular booster is higher above the venturi and is less responsive to low speed air, but reacts better to high speed air and is less restrictive air flow through the booster and venturii.
Someone said something about the vacuum ports that is correct, but If your engine is a mild 427 I seriously doubt you will need the 830. While it certainly has the CFM for the top end power, you will rarely need it on a street driven engine and a 750 cfm carb might be a better choice. I have not seen the entire combination you are using, but do the math. Plus if you go with the 750, you can use one of our new Street HP carbs that has all the benefits of the HP race carb with all the vacuum ports for the street, a shiny finish and calibrated for street use.
My two cents.
If you need to talk to a good carb guy in Holley Tech ask for Ray.
06-05-2005, 01:12 AM
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Where did the 427" stuff come from? Did I miss something? He says he has a 496, aluminum rect port heads, a pretty healthy solid flat tappet, 3.36's and 5 speed?
The 4779 is about the most universal carb out there. It will run well on a 302" Mustang up to a 454" Vette. You can easily make it do anything you want.
But a 496 is starting to want some airflow. His intake is the limiting factor for it, but I'd still give it some chance of getting some CFM especially with the dual plane.
I absolutely agree that Holley is the place to get carbs. If anyone can make one work they should be able to. I'm not a goant fan of BG's. I think they are OK, but not that great. The HP series of Holleys work very well on perky street motors.
Doug is definitely the EFI guy.....but what's his Nova got??
So far, there's a few in this group who have proven that a well set up carb can get awful close to efi in driveabilty,power and mileage. In fact Nick's 540 mileage has been almost dead even with a 454 EFI Vette, even with an extra 86 cubes, bigger heads and cam and identical gearing. Just think what it can do with some tweeking?
JIM
The 4779 is about the most universal carb out there. It will run well on a 302" Mustang up to a 454" Vette. You can easily make it do anything you want.
But a 496 is starting to want some airflow. His intake is the limiting factor for it, but I'd still give it some chance of getting some CFM especially with the dual plane.
I absolutely agree that Holley is the place to get carbs. If anyone can make one work they should be able to. I'm not a goant fan of BG's. I think they are OK, but not that great. The HP series of Holleys work very well on perky street motors.
Doug is definitely the EFI guy.....but what's his Nova got??
So far, there's a few in this group who have proven that a well set up carb can get awful close to efi in driveabilty,power and mileage. In fact Nick's 540 mileage has been almost dead even with a 454 EFI Vette, even with an extra 86 cubes, bigger heads and cam and identical gearing. Just think what it can do with some tweeking?
JIM
06-05-2005, 11:48 AM
#20
Le Mans Master
No doubt about it...if street driveability isn't a concern, the Holley Strip
Dominator or other single plane high rise will give him an HP boost.
Note that Holley puts the useable range at 4500-8500 RPM power band.
I also notice that Doug is using the stock big block hood. I kinda doubt a high rise single plane is gonna fit under there.
As to carbs...I been a Holley man for a LONG time (much to the displeasure of the Quadrajunk fans).
However, I am STRONGLY tempted to try out the Barry Grant Race Demon RS with the replaceable sleeves. Being able to change CFM to six different levels sure does make for one versatile carb.
I have also seen some negative posts about some of the newer Holley carbs. Specifically the "Street Avenger" series. No idea what the problems are, though, since I prefer the older versions of Holley stuff. Heck, I wish Holley still made a 3 barrel!!!
Dep
Dominator or other single plane high rise will give him an HP boost.
Note that Holley puts the useable range at 4500-8500 RPM power band.
I also notice that Doug is using the stock big block hood. I kinda doubt a high rise single plane is gonna fit under there.
As to carbs...I been a Holley man for a LONG time (much to the displeasure of the Quadrajunk fans).
However, I am STRONGLY tempted to try out the Barry Grant Race Demon RS with the replaceable sleeves. Being able to change CFM to six different levels sure does make for one versatile carb.
I have also seen some negative posts about some of the newer Holley carbs. Specifically the "Street Avenger" series. No idea what the problems are, though, since I prefer the older versions of Holley stuff. Heck, I wish Holley still made a 3 barrel!!!
Dep