Edelbrock Jetting?

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MOPARJ

MOPARJ

What can I upgrade now?
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I have an Edelbrock 600 cfm manual choke vacuum secondary carb on a 318 in a Dart. The motor is close to the same as my Duster (XE268 cam, stock cmpression 30 over pistons, headers, stock 318 heads with valve job). The jetting is a bit lean, as from time to time, it will bog a tiny bit off of the line and the plugs are a tad on the lean looking side (white). How hard is it to change jets on one of these performers? What is a good number jet and does anyone know what the base number is in this carb?

I am used to jetting holleys, but not these. Any help is appreciated.
 
To change jets;
Remove the step up spring and rod assembely. (You try to change these out to a thicker/leaner/ thinner/richer setting first.)

Remove the 3 spring clip that hold the linkages on. Choke, pump shot arm and choke lockout.

Remove the 10 screws holding the top down.

Lift top off. If the car was run before hand, the fuel under the top is pressureized and will spit out on all sides.

With a flat tip screw driver, un-screw the jets and use a #2 pencil to stab them to remove them without dipping your fingers in the bowls.

Reverse to install.

The number on the base of the carb tells you what it is. Post the number and I (we'll) tell you what it is.

Move the pump shot rod closer to the main body for a bigger shot of fuel to cure the bog. Make sure the correct measurment is on it.

Click this Edelbrock pages and go to instructions in the carb descriptions; http://www.edelbrock.com/automotive_new/misc/tech_center/install/carb_faq.shtml
You can open up a PDF on carb instructions.
 
Ive never used anything else except Carter carbs - TQ and AFB.

A baseline for a mild 318 with a Carterbrock AFB / performer would be:

.98 primary Jets
.94 secs

.73/.46 metering rods

HOWEVER - Before you start tearing jets out and swapping them -

PUMP SHOOTER - Your stumble is most likely your pump shooter position - move the pump shooter linkage rod (runs from the pump shooter 'arm to the throttle linkage)

Move it to the nearest hole in the "arm" to the actual piston - if you look at the pivot "arm", you'll see there's three holes - move the linkage to the hole nearest the piston/punger.....this should overcome your stumble.

This means more fuel is delivered per distance travelled by the 'arm" - like a fulcrum.

JETS - Jet sizes are stamped on the top rim of the jet - you'll need a magnifying glass...an use a brass or plastic jet removal tool - or be VERY careful with a screw driver - or you can 'scrub" the jet size stamping off the jets.

There will be two #s - one will be "120" - ignore that.
The other (with your carb size) should start with a "3" - for eg "396" = .96th jet.

Anything starting with a "4" is over 100th - eg "401" = .101 thou

If you can pull the jets and post the #s, that would help some.

Remember - the Primary jets in "carterbrock" AFBs should ALWAYS be larger in diameter than the secondaries.

(With a spread bore carb like a Holley 650 Vac its the opposite)

Metering Rods or "needles"

This is Carters version of a "power valve" - Two spring loaded rods pass through the primary jets. They are tapered so when they are sucked down by engine vaccum - the thick part of the "rod or needle" almost fills the primary jet orifice...this lets only a small amount of fuel through the jet.

When you accelrate - vaccum drops - the springs push the metering "needles" up, withdrawing the needle from the primary jet below it until only the thin part fills the jet orifice -

This makes for a bigger space in the jet orifice for fuel to pass through - thus a "richer" condition under "load" (only the narrow part of the needle is in the jet hole when vacuum drops) , thus richeneing the primary jet for mid level acceleration on the primary circuit.

These metering rods can be removed easily - two little top plates with small screws hold these SPRING loaded pistons in place. If you can slide the plate across without them springing out - be VERY careful - the # will be stamped on the side - post that up too.


Most guys start re-jetting before they need to - the accelerater pump shooter setting and the metering rod diameter are the first two steps in tuning before swapping out jets.

Hope that helps

M
 
rumble and moparmal are both on track here. good posts guys. once you do the eddys with the chart and the calibration kits, it'll be like second nature. don't forget to check vacuum and maybe change the step up springs.
 
You have a Edelbrock #1405

Google "Edelbrock 1405 owners manual"

Edelbrock tech center "Install Instructions" will appear.

Click on "1405 owners manual" and read.This is the manual that comes with Ede carbs.

You will need calibration kit #1479 to tune effectively.

Good luck!
 
I had the same issues with mine too, but after it has sat so long Im gonna rebuild and reset along the way. Ill definatrly keep this thread handy.
 
Be aware that Edlbrock calibrate their 600 cfm carbs to suit a Cheb 350 (out of the box) -

Mopars inherently like a richer setting per CUI (Why I dont know) so a baseline "out of the box" Performer woud suit a factory or VERY mild 318.

Even so, your vacuum readings will be different from the next guy , so there's no guarantee you wont need to richen the pump shot and possibly the metering rods even woth a smaller cui motor.
 
dodge freak said:
Good advice but I found its easier to check jet and metering rod sizes with wire drills and a mic..
Click to expand...

Yep i agree......I bought a drill set with fine drills to help work out jet sizes.


What I found also was that if you insert the fine calipers of a small digital vernier into the jet orifice on the "flush" side or "bottom" side of the jet - you can get a pretty accurate reading of the orifice diameter.

Its worth experimenting with anyway.......
 
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