MTFCA Forum

A while a back I cut a junk NH body in half. Has anyone removed any of the hump to improve air flow? The white portion of the hump could be removed to more closely resemble the straight through design. Has anyone tested this out?

Would it not mess with the venturi effect there forth reducing the fuel supply & atomization by slowing down the air velocity through the Carb?

Is not that what Montana 500 people do?

It would probably negatively affect low speed operation and sudden transition modes. I'd expect it to improve high speed performance. Any leaning -out effects might be offset by main jet adjustment and perhaps a slightly higher float level. Some kind of velocity stack might give good results within specific speed ranges. A compensated bowl vent might improve overall performance and economy, especially where an air filter is used.

Here’s what Bob Cascisa tried and his results— sounds like it’s worth giving it a shot!

http://www.mtfca.com/discus/messages/80 ... 1246901705

http://www.mtfca.com/discus/messages/80 ... 1249417571

http://www.mtfca.com/discus/messages/80 ... 1250997329

Dan Hatch wrote: ↑

Sun Jun 02, 2024 7:52 am

Is not that what Montana 500 people do?

Only a bit of 'smoothing' at the sharp corners of the venturi, and a guage is passed thru to check that the bore isn't changed, Montana 500 Rules are stock like sway back NH.




Do like the idea of boring the venturi Bob did years ago to a straight bore in the swayback NH , if one can't find the early straight-thru NH.

It works like trying to blow out a candle with the mouth wide open. You get more air but it doesn't blow out the frame. You get better action with the restriction which will suck in just the right amount of fuel for good mixture.
Norm

One thing to consider is that typical gasoline sold today is more volatile and vaporizes more easily than what was typically available in the mid 1920s. That ought to promote good throttle response with a somewhat less restrictive venturi. Ford wanted one carburetor that would give good drive-ability and good economy under a wide range of conditions, and do it on low grade fuel. With the fuels available today, especially non-ethanol fuels, a more open venturi ought to give good results. Some kind of auxiliary heat with a driver control would improve cold running and prevent any issues when running in cold, damp weather.
A carburetor with higher WOT flow will improve performance at higher engine speeds by allowing a denser mixture at higher speeds, and it will also improve compression pressure higher speeds.

It would make more sense , rather than take the dremel to the NH Carb, to adapt a carb such as an SU or Amal to the Model T intake to improve fuel flow.