Edelbrock Performer Series Carburetor

Table of Contents

Section 1 - Theory of Operation
Section 2 - Base Tuning
Section 3 - Power Tuning
Section 4 - Model Specific Info

Section 2
Base Tuning 

Before proceeding please ensure you have installed your Edelbrock Performer Series Carburetor according to the Carburetor Installation Instructions included with the carburetor

REVISING THE CALIBRATION

The Edelbrock Performer Series Carburetor is designed to allow quick and easy changes to the metering. Virtually any change imaginable can be performed without removing the carburetor from the manifold, and the most common changes may be performed in less than five minutes without removal of the airhorn (bowl cover).

To help you calibrate your carburetor, a CALIBRATION REFERENCE CHART has been designed for each model of the Edelbrock Performer Series carburetor. These charts each consist of two sections: A Calibration Table and a Rod/Jet Reference Chart.

After reading the Calibration procedures, the next step in calibrating your carburetor is to look at the Calibration Table for your model carburetor. Determine if you would like to go richer or leaner in the Cruise Mode and do the same for the Power Mode. Select the number that is closest to intersection of your Cruise and Power Mode selections. This is your calibration reference number. Now refer to the Rod/Jet Reference Chart that appears on the opposing page. Locate your calibration reference number to determine the rod/jet combination for your application.

For example, you have a 1405 Edelbrock Performer Series carburetor. You have determined (by reading the rest of the manual) you would like to go 1 stage lean in the Cruise Mode and 2 stages lean in the Power Mode. The intersection of these two lines lies on the number 21. This is your calibration reference number. Now look below the Calibration Table to the Rod/Jet Reference Chart. Find the number 21 under the REF# column. The jets you should use are .098 and the rods are .070 x .052.

Located at the very bottom of each Calibration Reference Chart is a guide for changing your Secondary Metering. This will be useful when calibrating the wide-open-throttle (WOT).

Before you attempt to establish a new calibration, be sure that the engine is in a sound state of tune. All ignition items must be in proper working order, including reasonably fresh plugs of the correct heat range. Timing should be properly set and the air filter element and fuel filter should be clean.

Proper fuel pressure should be verified and cracked or brittle vacuum lines should be eliminated. Many so-called "carburetor calibration" problems have been traced to another part of the engine system that was not functioning properly.

CAUTION: Be alert to carburetor flooding when fuel is first applied. Flooding can be caused by dirt, small particles of hose cuttings, floats and inlet needles which have settled during shipping, or by other conditions as discussed below. Each Edelbrock Performer Series carburetor is flow tested in the factory for both air and liquid flow so flooding is rare. However, for safety sake please observe this caution. When the fuel pump is turned on or when the engine is first started, watch closely for signs of flooding. If flooding is apparent, tap the body of the carburetor lightly with a rawhide mallet or the wooden handle of a small hammer. If flooding continues, pinch the fuel line hose to shut off flow, run the engine to clear the carburetor, and let the fuel line flow again. If flooding continues, pinch the fuel line hose to shut off flow, run the engine to clear the carburetor, and let the fuel line flow again. If flooding still continues, stop the engine. Clean up any raw gasoline and refer to the "Trouble Shooting" section of the Owner's Manual.

Parts and Equipment

Aside from ordinary hand tools, the following items are recommended.

Edelbrock Performer Series Carburetor Jet Set - Contains selections of Main Jets, Metering Rods, and Springs.

• Tachometer - If the vehicle is not equipped with a tach, the dwell meter style tach will be adequate. If neither is available, you will be able to use the speedometer in place of the tach for some of the procedures, but it will not be as convenient.

• Vacuum Gauge - Should be hooked up to read engine's intake manifold vacuum. Without a vacuum gauge, some of the calibration procedures will be more difficult.

  Changing Components

  Metering Rod and Step-Up Spring changes can typically be made in less than five minutes and without removing the carburetor. First, loosen the Step-Up Piston Cover Screws (See pg. 30) and twist the Step-Up Piston Cover Plates to the side. The Metering Rods and Step-Up Springs can now be removed and replaced if necessary. Be sure to replace the Step-Up Piston Cover Plate and tighten the Step-Up Piston Cover Screw when finished.

  CAUTION: Do not overtighten the Step-Up Piston Cover Screws! They should only be tightened to 12 to 17 inch/pounds. Excessive torque will weaken or snap off the screw heads. If this happens, they may fall into the carb causing serious engine damage. If an inch/pound torque wrench is not available, snug the screw until it just touches the plate, then tighten 1/16th turn more.

  To replace the Primary or Secondary Metering Jets, first, remove the Metering Rods and Step-Up Springs as outlined in the preceding paragraph. Next, disconnect the Choke Cam Connector Rod, Pump Connector Rod, and Choke Connector Rod (when applicable). Finally, remove the 9 Airhorn Attaching Screws and remove the Airhorn from the carburetor body. A standard screwdriver can now be used to remove the appropriate Metering Jets. Once desired Metering Jets have been installed the carb may be reassembled by reversing this procedure.

IDLE MIXTURE

The Edelbrock Performer Series carburetor has conventional Idle Mixture Screws (IMS) that provide a leaner A/F when turned clockwise and richer A/F when turned counter clockwise. The idle air flow is controlled by a conventional screw that opens the Primary Throttles. The following procedure should be used to set the idle mixture and speeds.

1. Fully warm engine and ensure choke is fully open.

2. Air cleaner in place.

3. Set desired speed with the air screw.

4. Adjust the IMS on ONE side to get the maximum possible RPM. Do not go rich beyond the maximum speed point.

5. If the above changed the idle speed more than 40 RPM, then readjust the speed.

6. Adjust the side OPPOSITE of that in Step 4 to get maximum RPM.

7. Reset the speed.

8. Carefully trim each IMS to again get the maximum idle RPM.

9. Go leaner just enough to get a 20 RPM drop in speed.

10. Reset the speed to the desired RPM.

11. This is a Lean-Best Idle Set. Setting richer than this will not improve idle quality or performance, but could tend to foul plugs.

Winter Fuel Idle Sets

During the winter months (in most parts of the country) the local fuel will be a "winter" blend that is very volatile, as an assist to cold-engine starting and driveability during warm-up. However, the high volatility has the disadvantage of allowing excessive vaporization of the fuel if the vehicle is operated in a heated area such as a garage. This can result in problems in the idle-set procedures since the carburetor's internal vents will allow this excess vapor to be drawn into the throats and enrichen the mixture. The idle will be erratic and not seem to be able to hold a set. To resolve this type of problem, it is advisable to perform the final settings outdoors after the vehicle has been stabilized with a drive of several miles.

Long Duration Camshaft

If the engine has a fairly radical camshaft it may require an excessive amount of throttle opening for idle and/or have low idle vacuum levels. Either condition can lead to poor levels of adjustability and erratic idles.

Another fix for the above condition is to run as much spark advance as possible at idle. If the distributor is fitted with a vacuum advance unit, connect it directly to manifold vacuum. If you are not able to employ vacuum advance for some reason, then the mechanical curve should have a low limit, which will allow you to use plenty of initial spark advance.

Measure the manifold vacuum at idle. If it is below 7" Hg, there is a good chance that the Metering Rods are in the up (rich) position. When combined with a high idle air rate this can cause the Nozzles to discharge fuel at idle. Use a weaker Step-Up Spring (see section on Step-Up calibration) to keep the Rods down at idle. With some cams, a stiffer spring (pink or silver) is necessary. Experimentation is the best way to determine which is best for your application.

CALIBRATING THE WIDE-OPEN-THROTTLE (WOT)

The best place to perform your WOT calibration is on a chassis dyno. If one is not available then consider a safe, legal driving space, such as a drag strip where you are given E.T. and MPH data.

1. Select an RPM Range to use in evaluating the WOT power. As a rule, use the highest 50 percent of the real power band. If your engine makes good power up to 5000 RPM, then 2500-5000 is a good range. If peak power is at 6500, then 3500-6500 would be a good pick. Be sure not to select RPMs that are higher than the engine's useful power band.

2. Accelerate at WOT from 1000 RPM below the range you have elected to a few

hundred over the range. Time the acceleration with a stop-watch. Be sure to time only the interval while the engine is sweeping through the selected range. Make enough timed accelerations to get a good average that is not affected by wind or grade.

3. Refer to the Calibration Reference Chart for your model. Find the richest Power Mode (Primary Metering) change you can make without changing a Jet -- a Rod change only. This will probably be 2 stages (8%) rich.

4. Change to the indicated Rods. Perform timed acceleration #2. Compare the times. Do not be surprised if there is no difference.

5. Compare the results of timed acceleration #2 to the base calibration and refer to the following section that best describes your situation:

Case 1: Faster than base calibration

• Change Secondaries 2 stages richer and perform acceleration test #3.

• If test #3 is the same as #2, you're done.

• If test #3 is slower than #2, change to 1 stage rich for the Primary and Secondary and you're done.

• If test #3 is still faster than #2, go to 3 stages rich Primary and Secondary and keep going richer until there is no change (or slower) in the times. Stay at the first "no change" level,  so that you stay with the richer of any two levels of calibration that have the same power.

   

  Case 2: Slower than base calibration

  Go to 1 stage lean Primaries and 1 lean Secondaries and perform acceleration test #3.

• If test #3 is the same as base calibration, go back to the base calibration.

• If test #3 is faster than base calibration, go to 2 stages lean on both the Primaries and the Secondaries. Keep going in the lean direction until there is no change or slower then back up 1 stage richer, so that you stay with the richer of any two levels of calibration that have the same power.

  Case 3: Same as base calibration

  Do not be surprised. Change back to base calibration.

CALIBRATING THE PART-THROTTLE

The Metering Rod feature used in the Edelbrock Performer allows easy calibration of the part-throttle without change to the WOT metering.

Cruise Mode: The power output is low, as in a steady cruise light acceleration. Manifold Vacuum is high and the Metering Rods are down in the lean position.

Power Mode: The power output is high, as in a heavy but not wide-open acceleration. Manifold Vacuum is low and the Rods are up in the rich position.

As explained in the "Theory of Operation," the Step-Up function modulates the Rods between the Cruise and Power positions.

The part-throttle calibration is more "individualized" than is the Wide-Open-Throttle (WOT). It is not measured by absolute numbers, but reflects the driver's feel for a particular combination.

Carefully evaluate the driveability with the carburetor at the calibration level determined from the WOT exercise. Drive at a variety of engine speeds and throttle openings looking for any flat spots or lean/surge conditions.

Cruise Mode

If there are any surge or flat spot conditions in the steady speed cruises or light accelerations, a lean condition probably exists. Consult the Calibration Reference Chart and change to 1 stage rich in the Cruise Mode. If it gets better, but not completely fixed, keep going in the rich direction. The Calibration Reference Chart will give you Rod and Jet combinations that are directionally correct or you may choose your own.

If the light throttle is satisfactory, trying going 1 stage lean in the Cruise Mode. If there are still no problems with surge or other indications of lean metering, do not hesitate to go to 2 stages lean in the Cruise Mode. A lean Cruise Mode has advantages in fuel economy and keeping the plugs clean. Keep going until you begin to notice driveability problems and then back up 1 stage.

Power Mode

Accelerations at part-throttle with low manifold vacuum (less than about 5" Hg on a vacuum gauge) are metered by the Power Mode. Avoid calibrating this portion of the engine's

operating range too lean as spark knock (detonation) and piston/valve burning can occur. If this mode has any lean driveability symptoms (surge or flat spots), it is too lean and should be recalibrated at least 1 stage richer.

CALIBRATING THE POWER MODE STAGING

The Step-Up function, which moves the Metering Rod to the Power Mode, is controlled by the Step-Up Spring. The base calibration has a spring which "stages" rich at 5" Hg.

If your vehicle has a mid-throttle driveability problem that is encountered as the throttle is gradually opened, but then goes away upon further opening, it may be possible to eliminate the lean spot by using a stronger Step-Up Spring. The available Step-Up Springs are listed in the following chart along with their respective "staging" point. It is best to select a new spring on the basis of vacuum readings, but in the absence of a gauge, try the strongest spring

(highest vacuum rating) to see if the problem goes away. If the drive problem is cured by the strong spring, try the next weakest spring as well. If the strong one does not help, then the calibration problem is related to the A/F metering stage of either the Cruise or Power Modes. Use the Calibration Reference Chart to help select another combination.

A complete set of these springs is available separately as Edelbrock part #1464.

CALIBRATING THE PUMP

If you encounter any hesitations or stumbles that do not seem to be related to the basic metering or have not responded to changes in the basic metering, move the pump drive link to one of the holes closer to the carburetor body. This will increase the stroke length of the plunger and result in more pump delivery.

FLOAT ADJUSTMENT

To properly adjust the floats in the EPS carburetor, two procedures must be followed. First, invert the airhorn cover (Figure 8) holding the airhorn gasket in place. There should be 7/16" between the airhorn gasket and the top of the outer end of the float. To adjust the float level, bend the float lever until the recommended level is attained. DO NOT press the needle into the seat when adjusting the float lever. Next, you should check the float drop (Figure 9). 

Hold the airhorn upright and let the floats hang down. There should be 1-1/4" ± 1/4" between the airhorn gasket and the top of the outer end of the float. To adjust the float drop, bend the tab on the back until the recommended float drop is attained.

CHOKE ADJUSTMENT

To adjust the choke piston linkage (Figure 10) open the choke valve and insert a .026" wire, with a 90 degree bend 1/8" from the end, between the top of the slot in the choke piston cylinder and the bottom of the slot in the piston. Hold the wire in position and close the choke valve by pressing on piston lever A until resistance is felt. The dimension C should be .100" between the top edge of the choke valve and the air horn. To adjust, bend rod B.

To adjust the fast idle linkage (Figure 11) place the fast idle screw A between the two notches on the cam. Close the choke valve as far as possible without forcing it. The dimension C should be 3/64" between the choke valve and the air horn. To adjust bend rod D.

Fast idle may be adjusted to manufacturers specifications (usually 1500 rpm) during normal choke cold operation. The fast idle screw A can be adjusted with engine off and throttle held open to allow screw head access. Recheck fast idle speed after each adjustment.

The length of time during which the choke will stay closed is determined by the position of the choke cap. As the choke cap is turned clockwise the choke will stay closed longer. To properly set the choke turn the choke cap to the leanest notch on the choke housing, tighten the choke housing retaining screws, and run the engine until normal operating temperature is reached. With the engine running, slowly turn the choke cap clockwise until the choke valve begins to close. Now turn the choke housing one notch counterclockwise (LEAN) and tighten the choke housing retaining screws. Periodic readjustment of the choke will be required as the temperature changes throughout the year. After each adjustment verify that the choke valve opens fully after the engine is warm.

SPECIAL CALIBRATIONS

The preceding calibrations and adjustments apply to carburetors used in general street applications. In the following extreme instances, special calibration procedures may need to be followed.

Off-Road

Although the Edelbrock Performer Series carburetor was not calibrated with hill climbing and other extreme off-road operation in mind, it can be made to perform superbly by substituting Edelbrock #1465 spring loaded needle and seat for the original needle and seat. The spring loaded needle and seat act like a shock absorber, reducing the possibility of flooding during off-road operation. After installation of the new needle and seat you must reset the float level to 3/8" and drop the float drop to 1-1/4" as outlined in "FLOAT ADJUSTMENT".

High Fuel Flow

When evidence of fuel starvation exists, first ensure that proper pressure (4-5 psi minimum) is maintained at WOT. If proper fuel pressure is supplied and fuel starvation still exists, it may be necessary to change the needle and seat to a larger size (#1466). Do not make this change unless absolutely required, as the smaller inlet is preferred for proper fuel control under most conditions.

High Altitude

Altitude has a direct effect on the operation of most carburetors. As the altitude increases, the air becomes less dense so a carburetor, originally calibrated at low altitude, delivers too much fuel and the engine runs richer. If the preceding tuning procedure is performed on an Edelbrock Performer Series carburetor, a proper high altitude calibration will result. If the vehicle was calibrated at lower altitude, however, and is to be driven at high altitude temporarily, it is not necessary to repeat the complete calibration procedure. Instead, use the rule of: "2% leaner per 1500 feet" and the Calibration Reference Chart for your model carburetor. For example, with a #1405 at baseline calibration (location #1 on the chart) and intended operation at 6000 ft. altitude, you would want 6000 divided by 1500 x 2% = 8% leaner calibration. That would be location #24 on the chart which would require only a rod and jet change.

Carburetor Specifications - All Models

* = Carburetor is certified to meet U.S. Coast Guard Requirements.

Blended Fuels

Typically, two types of blended fuels are available: Gasohol and gasahol. Gasohol is a blend of not more than 10% ethanol and gasoline. As long as there is no more than 10% ethanol mixed with the gasoline you carburetor will function properly. As the percentage of ethanol climbs above10%, a richer A/F ratio will be required. Also, because gasohol is more volatile than gasoline, hard hot starting and poor hot weather driveability may result.

Gasahol can be a blend of either ethanol, methanol or other alcohol with gasoline. Methanol blended fuel should not be used in your Edelbrock Performer Series carburetor as it will cause corrosion of the fuel system components. It can also cause rapid failure of seals, gaskets, diaphragms and pump plungers.

Always check to see if you are using a blended fuel. Although the pump may not indicate the fuel is blended, it is always advisable to verify the type of fuel the station carries.

Blown Engines

Two model #1405 carburetors should be used on engines with positive displacement superchargers, such as GMC 6-71 blowers or equivalent. The following calibration changes make an excellent starting point: Primary Jets - .101" (#1429); Secondary Jets - .101" (#1429); Metering Rods - .070" x .042" (#1450); Step-up Piston Springs - 5" (orange, stock); Needle & Seat assemblies - .110" (#1466).

This calibration has been tested on engines ranging in size from 350 c.i.d. Chevys to 440 c.i.d. Chryslers with good results.

Carburetor Specifications (Continued)

* = Carburetor is certified to meet U.S. Coast Guard Requirements.

Section 3 - Power Tuning

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