General Category > Quadrajet Carb Talk and Tips

Rear air door opening vs CFM

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70GS455:

--- Quote from: novadude on November 16, 2023, 07:24:48 AM ---How is air door opening measured?  From leading edge to back wall, or??

--- End quote ---
Actually I used the procedure in Cliffs book, that is to measure from the flap leading edge to the rear wall. So 1.2" means almost wide open

Pav8427:
If memory serves me right, arent specs for secondary rods shown in degrees of opening.
Would be interesting to rig up a degree wheel and compare degrees to degrees. 

Cliff Ruggles:
I measure to the rear as it's the same on all models.   Airflow is not the only thing to consider here.  When you go too far with the airflaps you are going to loose some signal to, or fuel flow from the nozzles. 

When I did airflow and dyno testing back when we wrote the book there is no gain past the numbers given in the book in terms of CFM or making more power on dyno pulls.

I backed up that testing at the track. 

We also found that at the largest opening recommended in my book the carburetor flowed 849cfm, not 800 like most folks regurgitate on the Forums and such.

Removing the outer booster rings on the larger models combined with the maximum open point yielded 897cfm.......

Frank400:

--- Quote from: Kenth on November 16, 2023, 10:42:24 AM ---This:

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that is one way of measuring, but is it me or this is NOT the way Cliff's numbers relate to in his book ? Just want to make sure I measured correctly when I followed Cliff's recipes.............

Kenth:
Following Cliff´s recipe measure like Cliff does.

I prefer and have always used Rochester instructions in my documentation of Quadrajets.

Both ways works if you know what you are using.

FWIW

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