Edelbrock models 1405 versus 1406 carburetors

Hi all.

The 1406 carb is calibrated for ecconomy (lean).
This does not only mean the jets are the only parts that are different between the two carbs. From my researches the venturies are also different between the two carbs both in the primary and also in the secondaries.
The manual does not state this even though the sizes are identical in the specs.
What the difference is that the discharge holes (orifices) are smaller in the 1406 both in the primary and also in the secondary venturies. The air bleeds and idle jets on the venturi clusters are different also. All this rearrangement alters how the jets meter in the carb. Do not try to mimic the 1405 jetting on a 1406. It will not become simply a 1405 carb. You will be somewhere in the unknown as to where your mixture will be. Although the rods and jets are interchangeable, the calibration of the main body will cause the rods and jets to meter differently. I wondered why there are separate metering kits for each carb. Each kit has the appropriate rods and jets to suit each carb's upper and lower limits. If you look at the PDF manual. you must stay within the parrallel shaded area designed for the carb. Edelbrock has got these graphs pretty close. Unless you have an air/fuel ratio meter, you must follow the manual. I purchased a 1406 carb for my 360 and it was much too lean (surging lack of part acceleration). I should have purchased the 1405 instead but I wanted electric choke. I went to step No. 23 on the calibration sheet in the manual and performance improved dramatically. The sweet spot was to go up to step No. 19 in the manual. The carb is right on the money. Throttle response is great! Its a keeper. As far as the secondaries is concerned, wide open throttle improved with the primary enrichment. further improvement of the secondaries will need a dyno or some passes at a track. There is no sign of leaning out at wide open throttle. Spark plugs are light gray in colour which also tells a good mitxture.
I was worried that I went too rich but like i said the carb venturi clusters are different between the two and play a big role on how the rods and jets meter between the 1405 and the 1406 Edelbrock carbs.

Regards
Billy D..
Valiant VC 360 1967
Edelbrock LD4B manifold
10.5:1 compression
228/235 degs @.050