Fwd facing Hood Scoop leaning out carburetors

[doug odom]

First, let me explain that I have spent many hours on the flow bench testing air flow with Holley carbs.
These are some FACTS I have found and proved many times.
The scoop is only a part of the function in flowing air into the carbs.
The space above the carbs after 2 inches is wasted.
 Holley carbs draw their air from the sides, not straight down.
The more area around the perimeter of the carbs the better.
The largest area air filter is best to calm and slow the air around the carbs.
The only trick I have ever found that did work was the carb-hat that helps smooth and direct the air into the carb.
( note; I have ruined more than one Holley trying the latest trickshit modification.)
After the air enters the carb and is mixed with fuel it still has to flow through the plenum, intake runner, intake valve etc. Many places that can affect the charge in each cylinder differently. 

 Doug Odom in big Ditch

[Leadfoot]

Yes Bob I do run nitrous on occasion . The problem seems to go away on nitrous it evens out ALL the cylinders. The problem is mostly just on the gas no spray. Are you coming to Speedweek this year ? Hope to get a chance to talk with you.

[Leadfoot]

I have a flat pan that I got from RJ race cars that is radius around the carbs. There is about 3 and half inches above the carbs and the pan is sealed to the scoop. A carb hat ? is the like a KN snub stack ? Also I'm using a Dart tunnel ram that has been cleaned up in the plenum area. 

[Bob Drury]

  Gary, I will be there minus race car.  I will for sure visit you and everyone else I haven't had time to chat with over the last sixteen years!
  Are you using a GM block or a Big M block?  Filled water jackets?  I wonder if maybe your block might have a core shift problem in the block or head?
  It might be worth sticking a camera in both next time its apart.
                                                                         Look forward to visiting and stealing all your speed secrets!
                                                                                  "One Run" Bob Drury

[Leadfoot]

Ok it will be good to see you Bob. I'm running a Merlin 3 block. There has been some great posts and a lot of ideas to think about. Thanks to everyone.

[doug odom]

Gary, Yes, Carb-hat was the first ones made. Not sure they are in business anymore. K & N stub stack same thing.


Doug

[Sumner]

.... I will for sure visit you and everyone else I haven't had time to chat with over the last sixteen years!...

Yes, let's make a visit happen this time. 

Helped a guy you know with his '36 Buick about a week ago here.  He was on a long cruise with a bunch of other guys and was having carb problems.  Neat car that was mostly original.  One of the few '36 cars that could do highway speeds today stock (well sort of, he runs an overdrive manual trans.),

Sum

[Stainless1]

   I will be there minus race car.  I will for sure visit you and everyone else I haven't had time to chat with over the last sixteen years!
  Look forward to visiting and stealing all your speed secrets!
                                                                                  "One Run" Bob Drury

Hey Bob, you can have one of mine for free.... Bring a car and make at least 2 runs...   
 

[Bob Drury]

  I am bringing my firesuit and helmet just in case a "Car Fairy" decides He is too old to drive................. hint, hint..............
                                                                                                            One Run, out.....................

[wobblywalrus]

It was a long time ago when we did this so my memory is fuzzy.  The best place for the ram air inlet was in the very front of the vehicle where it was not influenced by the various ways that air can travel around body work.  This was a bike so the intake was where the headlight normally was.

A duct ran back to a metal box.   Another duct exited this box and ran back to the carb.  A big flap valve hung on one side of the box.  It would open when the air pressure in the box got too high, like when running into a headwind.  This limited the ram air effect so the engine would not run lean.  It sort of worked.

Jetting was done by trial and error.  The jets were richer for ram air than without.

It was hard to tune.  Optimum main jet size was influenced by the speed the bike was traveling and to some degree, the direction the wind was blowing.  The experiment was abandoned.