Bob's Resource Website (2007)

Carter/Edelbrock AFB setup


 

An excellent reference for setting up your Carter or Edelbrock AFB-style carburetor is Dave Emanuel's "Carter Carburetors" published by SA Design Books.  However, for specific help in making these carburetors work well with in-line engines like Chrysler's slant six, I have had to do some research.  While I was waiting for the parts to arrive so I can try using a QuadraJet on my Offy intake, I was also trying to get my AFB to run a bit better.

The problem I had been having was a bog off the line. When the throttle was quickly cracked open at low RPMS, the low vacuum and air flow caused the fuel to drop out of the air, thereby creating a lean condition. After trying the a number of metering rod and jet combinations from my Carter Strip Kit, I found that the metering rods with the largest difference between the economy step and the power step seem to work best. Since Federal Mogul is no longer making AFBs and Edelbrock has started making a new and improved AFB with the name Performer, I checked out their metering rods. Edelbrock has some metering rods with even larger differences between their economy and power steps so I tried the next size-difference larger. The performance of my car improved once again and the bog has largely disappeared. To completely eliminate remnants of the bog, there is a still a larger-difference rod available. I wanted to avoid increasing jet sizes because that would affect my cruising fuel economy and I think there is room to make the cruising fuel mixture a bit leaner.

If you are using an Edelbrock or Carter AFB and are experiencing a bog at low RPMs, try experimenting with the following metering rods:

 
PN Cruise/Power Size Size Difference
16-241 (Carter) 0.0705 x 0.047  0.0230
16-690 (Carter) 0.0745 x 0.047  0.0275
#1459 0.075 x 0.047 0.0280
#1450 0.070 x 0.042 0.0280
#1455 0.073 x 0.042 0.0310
#1419 0.075 x 0.042 0.0330
#1449 0.070 x 0.037 0.0330
#1454 0.073 x 0.037 0.0360
#1458 0.075 x 0.037 0.0380

To maintain your cruising fuel economy, make your rod changes with rods of the same economy step. You can maintain a fuel mixture for a given rod step (economy or power) and change the fuel mixture of the other step by maintaining a constant area between the metering step and the jet.

Included in this site are tables that relate the flow areas of the various combinations of metering rods and jets.  At the bottom of this page are links to Carter and Edelbrock jetting tables which list the metering rods and jets available for each manufacturer.  Right-click on the link you need and select Open Link in New Window so that you can more easily follow the example below.

Let's use Edelbrock Performer Metering Rods and Jets for this example.  If you are getting good fuel economy with MR#1459 and you are using Jet#1429 (0.101), your cruising flow area is 359.4 square inches (to the 5 power). If you want to try using MR#1455, the closest flow area is with Jet#1428 (0.100) with a new cruising flow area of 366.9.  Jet#1429 and MR#1459 yield a power flow area of 627.7. Using Jet#1428 with MR#1455, gives a power flow area of 646.9. In this case, you increased your economy flow area by 2.1% while you increased your power flow area by 3.1%.

However, if you are using Jet#1429 and MR#1459 and you want to try MR#1419 with the same jet, your power flow area now increases by 5.6% to 662.6 with no change in economy flow area.

Carter AFB Metering Rods and Jets

Edelbrock Performer Metering Rods and Jets

The only difference between the two tables is in the part numbers.  The Carter table lists parts that were available in the Carter Strip Kit.  The Edelbrock Performer table lists parts that are currently available through Edelbrock.  The metering rods, jets, and springs will interchange between carburetors, provided that the carbs using only the two-step rods are considered.  The three-step rod carburetor is not offered by Edelbrock so don't try using their parts in one.  Be sure of the type of carb you have before you buy the parts for it!

 

 


These pages and programming contained therin are © 1996 - , Bob Johnstone and may not be reproduced without the permission of rfjohnstone at cox.net (Bob Johnstone) All Rights Reserved.
Some technical opinions are my own from experience, other informational data is from online sources with credits when available and while care has been taken to be as accurate as possible, it is offered only as a guide and caution should be exercised in the application of it.