Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - No change when adjusting air/fuel screws??
View Single Post
  #24 (permalink)  
Old 02-19-2012, 03:45 PM
75gmck25 75gmck25 is offline
Registered User
 
Join Date: Aug 2006
Location: Alexandria, VA
Posts: 1,747
Wiki Edits: 0

Thanks: 4
Thanked 64 Times in 62 Posts
You need to work through the Edelbrock settings step by step, and it starts with getting it to idle right. You probably do need to change to a higher step-up spring (maybe as much as 6-7" if you have a very high lift cam), but that will not help your idle.

- 12-14 degrees initial timing is a good start - just verify that is what you have.
- Disconnect the vacuum lines on the front of the carb and put caps on the fittings
- Make sure the brake booster is connected to the rear vacuum port, or that you have plugged the port
- make sure the carb gasket is in place the the studs are torqued down evenly

- Now turn the idle screws all the way in, and then back them out about 1 and 1/2 turns.
- Start the vehicle and set the warm idle speed to about 800 rpm.
- Follow Edelbrock's direction on setting the idle mixture screws. If they don't work (nothing happens when you turn them), then you need to fix the problem first. It may be a vacuum leak, or the throttle plates may already be too far open at idle.

Once you have a good idle then run up the RPM and verify that the mechanical advance works, and that it comes in with about 18-20 degrees at the RPM you want. Then connect the vacuum advance up to the manifold vacuum port on the carb and verify that the timing advances. Reset the idle speed (not mixture) to compensate for the additional timing.

The next item is the step-up springs. Follow Edelbrock's directions and swap them out until you get a good transition from cruise to power mode.

From there you can use Edelbrock's directions, or you can install an AFR gauge and use that for selecting the right jets and rods.

Bruce
Reply With Quote