Edelbrock: Timed Vacuum or Full Vacuum?

[EDMist]

Hey guys I took my truck out and drove it a bit for the first time. I rebuilt the motor and put a 1407 Edelbrock 750cfm on it. After reading the edelbrock website and finding the adjustment page I see theres 2 different vacuum ports a person can use...for Full or Timed vacuum. The 390 runs good but idles rough. when i advance the distributor it settles a little bit. Any ideas on which vacuum port i should be using for this motor.? Any tune up or timing tips will be very helpful. I put the new timing chain in the truck myself but for some reason i cannot run the timing at 8BTDC. Its more like 20 BTDC. Any info or ideas would help me tremendously. Thx.

[fmc400]

Typically you'll want to run the vacuum advance from timed (ported) vacuum. Rough idle is usually caused by a vacuum leak, improperly adjusted mixture, or wrong idle speed setting. A vacuum gauge would tell you what's going on.

[EDMist]

Ive never used a vacuum gage...How do they work?

[Tees77f150]

How to Use and Interpret a Vacuum Gauge


Check this out, it is the best way to learn about how to use a vacuum guage.

[pidaster]

Originally Posted by Tees77f150

How to Use and Interpret a Vacuum Gauge


Check this out, it is the best way to learn about how to use a vacuum guage.

That was some good info. Thanks.

[EDMist]

That was a great link...lots of info was gained this day.Thx

[montana_highboy]

You want to pull ported vacuum for v/a on a stock or semi-stock motor, manifold vacuum will pull in all your v/a at idle defeating its very purpose, unless you're running a radical cam and need to smooth out an erratic idle stick with ported vacuum for your vacuum advance.

[zak8tac]

And just to re-iterate the fact, I have the same carb and the port you want to use is the passanger side port.