Thread: Idle circuit, Timing Related??

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What about 4-corner idle on a BBC 454, hydraulic roller 218/226 @.0502, 112 lc, mid-500 lift? One person advised a good starting point is all 4 screws open 1/2 turn, another suggested 1 turn. I have just set the timing (total 38 deg) which is where the best dyno results were, and 1/2 turn seems better than a whole turn. Guess I'll have to get the vacuum gauge back on it. Do you turn one primary screw to get best vacuum, then do the other 3 the same? I'm assuming they should all be more or less even?
Chris

Sorry guys,
DennyW already answered my questions on an earlier thread! Short memory!!
Chris

This is from the edelbrock web site:

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.