Sorry to bring up an old thread, however a friend just called and told me about it so now seems like a good time to join the forum and fill in some gaps regarding the twin blade carbs. I'll share as much information as possible and hope I don't step on any rules. Sorry in advance for the long post.
btw: I like the info on here, seems like a group of sharp guys.
I am the designer and patent-owner of the 'twin blade' carb (Carburetor #D748149), the 'upper fuel jets' (Fuel Jet Tube #10036357) and the '2-piece fuel bowl' (Fuel Bowl for Carburetor System and Associated Methods #9404442). The first 2 patents are used in all twin blades and the 2-pc bowl is a popular option.
There are two (2) companies licensed to manufacture, sell and/or use the patents shown above: Phelps Machine R&D (PMRD) and Decker Machine (DM Performance).
I also designed & tested what is now called the BX4 Extreme for BLP before leaving in order for them to have a new design. It was important to me for the employees there to have success and also allowed me to do a direct comparison between the 4-bbl and the twin blades.
A common mistake made when calibrating a twin blade is to underestimate the air flow and booster signal. (I made this mistake with the first few...) I get it. It's a small, lightweight carb and seems unassuming when looking at it. Most try to use their standard 4150 calibrations (850, 950, etc) with maybe a tweak or 2 and it's just lean all over. These carbs flow the same amount of air as a 4500, so it makes sense to calibrate it like a 4500. After doing this, everything will fall into place. And for the record; I've tested these things against 4500's for a long time now and when both are well calibrated, the twin blade nearly always outperforms a 4500 with reasonably close air flow. Tony Morris (an agent for PMRD) is having great results when replacing 4500's with twin blades on a variety of fuels, engines and cars. There is also a significant weight difference.
The twin blades also have better fuel distribution than 4-bbls due to the shape. I could type it all out to explain, but I made a short tech video that explain why this happens. A new builder in TX recently built a 1400 twin blade and tested it on his 572" Mopar dyno engine. All carbs require a 2-4 jet size difference from side to side on this engine, but the twin blade made the best power and best afr readings when jetted straight up. We've seen this over and over on nearly all cars and it's due to the venturi/throttle bore ratio and shape.
Drivability with a twin blade is one thing that everyone likes. There is normally a significant increase on the power curve from below peak tq to peak hp over a similar sized 4-bbl. It's a well shaped curve with no peaks or valleys. These carbs have become quite popular with the road-racing crowd due to the smoothness and I have a close friend who replaced his EFI unit with a twin blade on his C3 resto-mod Vette. He said it drives better than it ever has now.
Let me know if you have any more questions. Thanks for reading...
Mike
PatentsTwin Blade InfoTwin Blade Physics
