Vacuum advance vs mechanical advance

[JWMcCrary]

I realize when running a big cam you don't want vacuum advance, but the way we setup our rigs in most cases either will work fine, so I am told. What are the pros and cons of each?

 

[68ford]

with vacum advance you still have mechanical, vacum is strictly low load advance, give it gas it shuts off, mines plugged off and i run more initial, but if your looking for freeway milleage you should run one.i have a pretty big cam 270duration .500 lift, and i have real good vacum above 1500 under light load so it would still work great on the freeway, i know this because my vacum wipers still work the same with the built motor above 1500.

 

[68ford]

i shouldnt say it shuts off, but is directly related to throttle, where mechanical is rpm related regardles of load.

 

[shifter]

You can find alot of posts on this topic here if you search. I also learned alot about this subject at hotrodders.com

 

[jarch]

Do you guys run ported or manifold vacuum to the dist? I have ported from the carb, and it doesn't pull any vacuum until the engine revs above 2000 rpms or so. Manifold vacuum pulls all the time under light load......

 

[ransil]

It should be ported. total advance should not exceed 36 degrees.