Hello everyone,

I have a 1979 One Ton with a 400 motor (4x4 and automatic). The previous owner put an Edelbrock 1406 on it. After doing some research, I understand the edelbrocks have mechanical secondaries. The truck idles like crap but works great at speed, so my conclusion is that the mechanical flap on the secondary is pushing too much gas. If I lean it out on idle, it may not do well on the highway. I'm going to get a Holley 600 CFM with vacuum secondary. That ought to help smooth out idle. I hope!

My ignition system looks like a hodge podge of stuff from different vendors. Any support for a full MSD system while I'm at it?

I'm not looking for power, I just want smooth and steady...

 

edelbrock are vacuum secondary units, however there is no tunability to the secondaries. They rely on weights that open as air flow is increased, so to tune then weight must be removed or added. Holley has fully tunable secondaries, allowing spring rates to determine opening characteristics. I would be surprised if the secondaries are causing idle issues.

 

Start with a tuneup. Also the Ford ignition is awesome no need to change.

 

F-250 Warhorse. Thanks for the note. Clearly I am a newbie and trying to gather all of the information I can. I just watched an Edelbrock video and you are right! There is a lot of misinformation out there as I am certain you all know better than me. Maybe I just need to adjust the idle speed. I was messing with the air/fuel mixtures but that didn't seem to do much. I put in new plugs and it seemed to help a little. It just idles so rough. butter smooth once it gets going...

 

Does the choke work?

 

Throw a vacuum gauge on the engine and adjust the idle mixture to maximum vacuum. Try to keep the idle speed around 800 rpm, in Park.

If the idle speed rises as you get the mixture dialed-in, adjust the idle speed back to 800 and start over.

When you get the mixture dialed-in, put the transmission in Drive, and adjust the idle speed to 650 rpm.

 

I must have a vacuum leak. I need to crank the idle to 1500 RPM to get to 15 inches of vacuum. At 1000 RPM and an air/fuel mixture that seems O.K., the vacuum reads around 12. I think that's it. Thanks.

 

Take the air screws out blow some carb cleaner in the passages and the ports on the top/front of the carb.

 

Set the idle to factory RPM (650?) and observe the vacuum gauge. Want to see 18" to 20" steady at Sea level.
If only 14" or 15" steady or erratic, bouncing around, etc, you have some 'vestigatin to do.