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BLP Twin Blade carb

Posted: Tue Nov 07, 2017 9:24 pm
by Dragsinger
Anyone racing with the BLP twin blade design?

Re: BLP Twin Blade carb

Posted: Tue Nov 07, 2017 10:47 pm
by jmarkaudio
I've built several, still have an E85 one built I run on a test car, and one left to build. BLP doesn't sell them anymore, you have to get them from Mike Laws at Get'm Garage or I can build one.

Re: BLP Twin Blade carb

Posted: Tue Nov 07, 2017 11:06 pm
by fastvette
Is there any advantage to the twin blade carb?

Re: BLP Twin Blade carb

Posted: Tue Nov 07, 2017 11:18 pm
by John Haskell
Ask Brandon Huhtala. NHRA B/A & C/A. Look it up.

Re: BLP Twin Blade carb

Posted: Wed Nov 08, 2017 2:26 am
by cjperformance
www.enginelabs.com/engine-tech/carburet ... ng-design/

A bit off topic but has anyone used one of these Silverback carbs ?

Re: BLP Twin Blade carb

Posted: Wed Nov 08, 2017 9:13 am
by Frankshaft
fastvette wrote:
Tue Nov 07, 2017 11:06 pm
Is there any advantage to the twin blade carb?
The advantage is for classes that must run 4150 carbs. If no one else is running one, and you get your hands on one, you will have an advantage, as they flow more than most dominators. Or, there are classes that give weight breaks for 4150 carbs, although, some rules guys have caught on, and now there is no weight break for them.

Re: BLP Twin Blade carb

Posted: Wed Nov 08, 2017 11:52 pm
by jmarkaudio
Frankshaft wrote:
Wed Nov 08, 2017 9:13 am
fastvette wrote:
Tue Nov 07, 2017 11:06 pm
Is there any advantage to the twin blade carb?
The advantage is for classes that must run 4150 carbs. If no one else is running one, and you get your hands on one, you will have an advantage, as they flow more than most dominators. Or, there are classes that give weight breaks for 4150 carbs, although, some rules guys have caught on, and now there is no weight break for them.
Actually not. The original Little Bo, now called a 1200, dry flow tops about 1250 with a machined down leg, with custom annulars I've hit 1220. A stock 1050 Dominator will flow about 1250, with some work right at 1300 CFM. The big advantage is the ability to run it on a 4150 intake and flow almost as much as a 1050 Dominator, HP difference is negligible. There are two bigger versions coming out that will fit a Dominator intake and will dry flow up to around 1600 CFM. With billet these days you can get up to a 2.800 throttle blade flowing up to around 2000 CFM, so size can be made to suit.

Re: BLP Twin Blade carb

Posted: Thu Nov 09, 2017 8:37 am
by Frankshaft
Thanks for the clarification. I was thinking the twin blades could flow more, because of the big 4 barrel billet 4150's. I have used one of them from BLP for a truck pull deal, carb worked VERY well. We also use a billet 2.45 blade dominator from Devane that works incredibly well. You can put a 2.8 in the 4150 body?

Re: BLP Twin Blade carb

Posted: Thu Nov 09, 2017 10:03 am
by jmarkaudio
There is an oval blade due soon like the big 4150's. And no 2.800, 2.200 is the biggest in the large 4150, I've built 2 of those.

Re: BLP Twin Blade carb

Posted: Sat Nov 11, 2017 10:17 am
by Frankshaft
How much gain from say the 2.45 to a 2.8 on a spread port bbc that spins 8500? 15-20? Maybe a bit more? I have heard they are finicky, like, you really should have egt's or a wide band and constantly adjust. Some say its not worth the headache. Thoughts? Also curious, what do you think of that new bowl set up from I think its dam best.

Re: BLP Twin Blade carb

Posted: Mon Nov 13, 2017 10:33 am
by jmarkaudio
I wouldn't use a 2.800 on that engine, 2.400 is plenty. The guy running the 2.800's are spinning in the 9000-10,000 range, and in a couple cases the 2.800 is still too big. The booster also needs to be redesigned as well for a venturi that large, I've been working on that. The 2.800 would be better suited for 700" plus engines that can pull more velocity thru the carb. What some don't realize is a larger carb doesn't necessarily pull more air, it just takes less power to pump air thru it, less pumping losses. And it's a balance, lowest pumping losses without significantly hurting distribution of fuel. Distribution with a single carb is improved with a more restrictive carb, higher vacuum/pressure difference helps vaporization, helps keep fuel in suspension. But it does it at the expense of pumping losses.

Re: BLP Twin Blade carb

Posted: Tue Nov 14, 2017 6:15 pm
by 340king
That's why I always suggested to the bracket racers that they might want to use a slightly smaller carb to improve consistency. The small changes in air didn't affect the engine that was already starving a little for air as much.

Re: BLP Twin Blade carb

Posted: Thu Nov 16, 2017 9:04 am
by steve316
What is the advantage of running a 2.4 or larger blade and then having to run a skirted booster to make it work.

Re: BLP Twin Blade carb

Posted: Thu Nov 16, 2017 9:59 am
by jmarkaudio
steve316 wrote:
Thu Nov 16, 2017 9:04 am
What is the advantage of running a 2.4 or larger blade and then having to run a skirted booster to make it work.
Good question... Let me know if anyone else can give you an answer that makes sense...

What I see on the flow bench is that the skirt does nothing more than make the carb smaller. It does make the booster signal higher, but only because it's making the carb smaller. If you swap from a straight to a skirted banjo using the same booster insert on a flow bench, and use the same bench depression, the signal is the same. In the case of the large skirts it can be less, the large flair on the skirt causes turbulence and kills flow and signal. While there may be isolated cases with poor induction distribution that this may help, causing turbulence in the carb is not conductive to making power.
The
As a result I try to size the carb for the engine it's on. I tend to go a tad larger than some might suggest, but I use custom annular inserts in all my builds that provide a better signal, atomize the fuel more thoroughly. The goal is to use as large as the engine will tolerate and still atomize/vaporize the fuel sufficiently for even distribution. When it is distributed more equally it uses less fuel, displaces less air. And a more homogenous mix also burns quicker, more completely, and needs less timing to do it.

Re: BLP Twin Blade carb

Posted: Thu Nov 16, 2017 2:09 pm
by Mike Laws
jmarkaudio wrote:
Thu Nov 16, 2017 9:59 am
steve316 wrote:
Thu Nov 16, 2017 9:04 am
What is the advantage of running a 2.4 or larger blade and then having to run a skirted booster to make it work.
Good question... Let me know if anyone else can give you an answer that makes sense...

What I see on the flow bench is that the skirt does nothing more than make the carb smaller. It does make the booster signal higher, but only because it's making the carb smaller. If you swap from a straight to a skirted banjo using the same booster insert on a flow bench, and use the same bench depression, the signal is the same. In the case of the large skirts it can be less, the large flair on the skirt causes turbulence and kills flow and signal. While there may be isolated cases with poor induction distribution that this may help, causing turbulence in the carb is not conductive to making power.
The
As a result I try to size the carb for the engine it's on. I tend to go a tad larger than some might suggest, but I use custom annular inserts in all my builds that provide a better signal, atomize the fuel more thoroughly. The goal is to use as large as the engine will tolerate and still atomize/vaporize the fuel sufficiently for even distribution. When it is distributed more equally it uses less fuel, displaces less air. And a more homogenous mix also burns quicker, more completely, and needs less timing to do it.
All true...

Mike