Allright, I've been playing with my Edlebrock carb (1406) over the last 6-8 months. I've just done small changes at a time, and sorta went by a trial and error thing. I originally was going to set mine up to have the same settings as Edelbrock's 1405 Performer carb since that one was supposed to be tuned for more performance from the factory. Anyways, I'm trying to actually get the tuning down to a science now, and I've got a few questions.

Now, I'm looking at the Edelbrock tuning chart for the 1406 carb and it talks about the "main jet" size. I noticed that on all the Edelbrock carbs the primary jet is smaller then the secondary jet. For instance, my carb came with .098 primary (closest to front of carb) and .095 secondary (back of carb). Unless I'm understanding this wrong, wouldn't you want it the other way around, so it richens up in the higher rpm range or when you get on it? So now I'm running .098 primary still, but stepped up to a .101 size secondary jet to go 2 stages richer. My only other change from stock was to a 5" orange spring instead of the 4" yellow and I'm still running the stock .075" x .047" metering rods. So I'm wondering, what exactly did I change by putting in the .101 secondary jet? It's richer I know, but would that be during cruising mode as Edelbrock calls it or would that be during power mode?

Another part where I'm confused is when they say "main jet" on their tuning charts, would they be reffering to the secondary or primary jet? I'm wondering because if they call the primary the "main jet," then I should be going with a .073" x .042" rod (according to the chart). However if they refer to the secondary jet as the "main jet" then according to the chart they give me, I should probably switch jet sizes because although the tune will be slightly richer during power mode, it's a very signifigant amount richer during cruise mode, which I don't need.

Thanks for any help you can provide, and if what I'm asking is unclear, just lemme know.

-Brandon

 

The main jet on the charts is the primary jet. It's larger than the secondary jet because it has a metering rod sticking through it, which makes it effectively smaller.

 

Okay, so if everything was stock and I simply changed the secondary jet to .101 from .095, what exactly would I be changing? WOT calibration or what? Is it even worth changing that jet, because edelbrock makes no mention of it in their tuning chart. Am I better off just going back to the stock .095 size jet?

 

The charts are for changing the primary calibration. The primaries are more complicated because they have the cruise and power modes depending on the rod size and position. The secondaries are simpler because they're just a simple hole. There are charts in the manual for the secondary calibration, but they're just a simple list of sizes. Changing the secondary calibration should only really affect the WOT tuning.

If you've gone from .095 to .101, you've made the secondaries 2 "stages" richer, or about 8% richer according to the chart for the 1406.

 

Another question, when I went from a 4" yellow spring to a 5" orange, what exactly did I do. I changed it because that's what the 1405 carb was running from the factory (they all seem to run that spring). I know it has to do with when the rod are in the up or down position, but are they in the up position sooner or later? And what is it affecting if they're up sooner or later?

Also, I moved the accelerator pump from the middle hole to the top hole, what would that do also?

-Thanks, Brandon

 

The spring controls at what vacuum level the metering rod moves from the cruise to the power step. A heavier spring will raise the rod and richen the mixture quicker when the throttle is opened.

Moving the accelerator pump linkage changes the pump shot volume. Putting it in a hole closer to the body of the cam increases the volume.

 

Allright, hopefully I'll get a chance to try some of these changes today.

 

let us know what happens im using the same carb on a vortec 350 and i can tell its running lean. i changed the rods and springs but havent changed jets yet.