Edelbrock Carburetor Tuning

Carburetor tuning has always been a black art to me. I recently swapped out the 2bbl on my stock 318 (other than dual exhausts) for a new Weiand manifold and Edelbrock 4bbl. The motor had really nice throttle response with the old 2bbl, but stumbles and goes flat with the 4bbl. I have a tune up kit for the carb, but the instructions might as well be in Latin. For starters, should I just change the two plunger springs to the strongest ones?

One thing you need to post...is ........stock cam in the 318 or what?,,,,where is the timing set?

which eddy carb....I have a hard time see what model it is from Vegas,,,,,,,,,,

Was this a brand new, in the box, carb, or just new to you? Do we we know what size it is?(CFM) A picture would help, then we can begin proper adjustments and repairs if needed.

It's a new Edlebrock Model 1405 600cfm 4bbl on a new Weiand model 8007 dual plane manifold on a stock 1974 Duster 318 (except for dual exhausts).

Pictures would be ideal.
What is the timing set at?
What do you have the air/fuel set screws at?
Is it an automatic?
What/how did you modify the kick down rod between throttle bracket and carb?
Do you have the Mopar adaptor on the carb?
Are you still using the 2bbl throttle bracket?
Pictures would be ideal.

dICKj said:

It's a new Edlebrock Model 1405 600cfm 4bbl on a new Weiand model 8007 dual plane manifold on a stock 1974 Duster 318 (except for dual exhausts).

Click to expand...

On my 318 the 600cfm stock squirt nozzle was too small I upgraded to the 43 size nozzle bog went away although my 318 was not stock, But in your case on the pump shot arm move it to the bottom hole see if the flat spot goes away. Also I would recommend using the silver springs to match your stock vacuum signal on the stock 318.

dICKj said:

For starters, should I just change the two plunger springs to the strongest ones?

Click to expand...

I disagree with most of the questions above.
For starters you need to isolate the issue.
By breaking up the different situations, the circuits that need adjusting can be isolated.
On these carburators, many of the systems interelate. Because of that the sequence of isolating is important.

heres how to break it up and check each situation.
0. Warm up. The choke system and fast idle system changes everything. With a new carb, get it idling and come back this later.

Once its warmed up.
1. Slow idle. Slow idle in gear if on an automatic. Goal here will be slowest rpm that will idle strong and smooth in gear. On a stock engine this should be anywhere from 500 rpm to 750 rpm on some smogged engines. it will take several tries. Get it close. Come back to it again later when the engine has been driven.

2. Low speed system. Slowly accelerating from stop or low speed. Specifically opening the throttle slowly. This reduces or eliminates the need for pump shot.

3. Low speed cruising. Driving at a steady speed and rpm on fairly flat ground or slight uphills. Anything 45 mph and under.

4. High speed cruising. Driving at a steady speed and rpm on fairly flat ground or uphills. Anything 65 mph and over on flat. Less on uphills. Exactly where the main system fully takes over is hard to know without testing for it.

5. High speed system response. Firmly part throttle acceleration at highway speeds (like interstate passing) or uphill.

6. Step up system. Increasingly open throttle at speed. Probably best from at least 35 mph. Every increase of throttle opening should result in a corresponding increase in power.

7. Rapid acceleration from stop or very low speed. This is testing pump shot. it can only be settled upon after the steady and slowly acceleration tests are good.

8. Full throttle acceleration at high speed. This is the test for secondary opening characteristics.

This will make ALOT more sense if you watch the video and/or read Chrysler's late 60s Master Tech on Carburetor Fundementals
Master Technician Service Conference - Chrysler's Training for Mechanics

Go to edelbrock.com & look for Brochure #00341. I printed one out for a friend earlier this week, but I don't remember if I went to the site or just stumbled on it.

The FIRST thing you need to do is verify that the float level [ 7/16" ] is correct. Most E carbs I have used had incorrect FLs, maybe bounced around during shipment.

Unlike brand H [ & clones ], you will not need new gaskets if you are careful.
And what does 'go flat' mean?

If the Weiand intake has a cut out in the plenum divider, the pri jetting may need to be richened slightly.

Yes yes. Fuel level is the FIRST thing!

Only then you can go on to tuning the circiuts.
How to read carb calibration chart?