Advantages of twin blade carbs?

[bigblockmark]

What if any advantages are there with the twin blade carburetors? Both the 4150 and the 4500.

In specific, for myself and for a friend. 4500 1050ish size. gas and alcohol. We both have BBC 3000# bracket door race cars. 482" for alcohol and 496" for gas. Looking for improvements in consistency, throttle response and shift recovery. Better ET and MPH would be nice, but really looking to have a better package of reaction times and ET consistency.

Is there any proof this would be possible with 2 blade versus 4 blade? Already tried single blade and nothing there and slower on alcohol versus gas on 2 carbs built by same company.


We looked at the 2 blade style at PRI recently. They are beautifully built. The sales people touted better response and repeatability along with increase in horsepower. Also told us 2 blade design eliminates turbulence in the 4 blade 4500 design where the hole is between the blades on the underside. Up where the internal secondary linkage is. Seems like any 4 hole spacer or plate would eliminate that?

Would skirted annular discharge boosters work well with twin blades? Are twin blade 4500s too large in CFM for 482"-496"size bracket engines operating at less than 7500 RPM in 1/8 mile drag racing?

i believe Mark W. has experience with these 2 blade style. I am aware of issues over rights to build these 2 blade carbs.

[mike laws]

https://www.youtube.com/channel/UCu7iEmRJMxtMJylpXV09W6g

Hope this helps. I'm also working on write-ups for each.

[bigblockmark]

Very good info. That is exactly what I was looking for Mike.

In the low pressure area between the 4 barrels, have you tried bolting a taper piece, like a blend spacer, down into the plenum of the intake to reduce the low pressure area to see what effect it would have?

Is it practical to size a 2 blade for say a 496" BBC engine 800 HP and have interchangeable parts to go back and forth between alcohol and gasoline?

[GTO Geoff]

While an oval blade for pri & sec is new, the oval blade concept is not new.

Holley had a 'three' blade 950 cfm carb with a single oval blade in the secs. Even before that in the early 60s, there was a three blade AFB carb used on Pontiacs that had a single oval blade in the secs.

[mike laws]

[mike laws]

[ojh]

I see them more where rules allow only a 4150 baseplate and you have big inch motor like a stock class pulling truck, they are sensitive to part throttle loads where you're trying to get 'on top' of the sled, easy to tune for WOT. I think it'd be touchy to get one working on a footbrake drag car. They are well crafted, sexy machining.

[Rat Bastid]

[TMCarbs]

You can purchase twin blades from several companies, LRC VRC TRC DeVane and myself TMC are just a few that sell legal Twin Blades all will give you great results, you can find TMC on Facebook!

[mike laws]