When tuning a Carter/Edelbrock four barrel carburetor its tough to change either the cruise or power mixture setting without messing up the other. This chart can be used to select different needle and jet combos by looking up desired mixture settings.

How do I use this silly thing?

First, grab a copy of the chart itself : carterJetSelector.pdf

Carter/Edelbrock carburetors use needles that drop into jets to set cruise and power fuel mixtures. During cruise, the needle is sitting in the jet restricting the fuel. When the throttle is opened up, the needle is pulled out of the jet so only the jet is restricting the fuel. This gives us two fuel mixture settings. Power setting uses the area of the hole in the jet itself, cruise setting is this same area, minus the cross section area of the needle. Confusing..

On top of all this, the part numbering scheme is.. Well, not terribly useful as far as we could see.

So we took every possible jet and needle combination and put them on the jet selector chart. Not only that but, they have been sorted by the resultant areas. Resultant areas? Think of it as mixtures. The bigger the number, the richer the mixture.

Open up your carb and look at the part numbers for your needles and jets. Find this set on your chart.

Lets pretend you are using... 16P-485 & 120P-383

OK? This gives a cruise Mixture of 0.00209 and a Power mixture of 0.00329

These numbers are actually the resulting areas of the jet needle combos.

Need to go richer on the Power and stay the same on the cruise?

Try the next one up : 16P-691 & 120P-392 This combo will change your cruise very little while giving a good increase in the Power mixture.

Need to lean out the cruise and hold the power the same? Try : 16P-544 & 120P-386

Or perhaps further up the chart will give you a better fit? Look at your chart and see.

We hope this helps. It sure did around here!