Hey guys,
Just wondering, the other day i was workin on my car, and when i went to test drive it i forgot to hook up the vaccuum advance. There was no hose attached and the ports were open. But to me, my car seemed to have more power. Can this be or maybe my timing is slightly off?

Sounds like you had it on the wrong port before.

Maybe your timing is set wrong.

More power at WOT or at part throttle? Sometimes the vac adv. adds too much timing and causes the engine to feel sluggish at part throttle, but should be no difference at WOT.

well it seems to have more power throughout the throttle range. to add to that, it sounds pretty damn nice with line disconnected

Sounds like your carb is too rich and the extra air from having the vacuum line disconnected and open leaned you out enough to gain some power.

You can test this by plugging the vacuum line and see if the power decreases. If it does, then your carb is way rich.

Risky at best because you could end up running too lean.

Adjust/tune your carb to run with the vacuum line hooked back up.

I'm going through the same thing. A machine shop told me to unplug mine because it gave to much advance at part throttle. I still don't understand really why it's even there. At wot theres no vacuum same as at idle unless your connected to the full port of the carb. My mechanical advance in my distributor seems to be enough advance. Someone please why the vacuum advance?

What problem were you having that caused the machine shop to tell you that? How did they determine that? What is your initial timing set at now? What is your Total mechanical timing set at and at what RPM?

Check to see how much advance your vac. can adds - mine added 17 deg (+36 total mech. adv.). A 10 degree can may work ok, but right now mine is unplugged. I remember reading that 52 deg. total will give best mpg. When I tried it I saw less than 1 mpg improvement (in the city) and the part throttle response was very sluggish, the motor was fighting itself because of all the timing advance.

My total mechanical is 36 deg and by what I see on my light my initial is 18. When I plug in the advance and give her gas the vacuum pulls it another 10 deg at around 2800-3300 rpm.

Although the initial seems a tad high (the mechanical should be in the neighborhood of 20 degrees which would yield a Total mechanical of 38 with 18 degrees initial) if you have an otherwise stock engine, it doesn't sound out of line.

Getting an additional 10 degrees by hooking up the vacuum advance sounds correct and 'normal'

Since you didn't mention any of your other engine specs, I'd hook the vacuum back up and road test it. Drive at a moderate speed up a slight hill in high gear. If the engine 'pings', retard the timing 2 degrees and test again. When it no longer 'pings' you are good to go!

Thanks Frisco I read your past posts on timing very helpful. I don't know how much the heads and cam effect timing, but I got a 355 64cc rpm heads, four eye flat tops, 284 adv. duration 480 gross lift cam, 770 holley. I will guess around 10 on compression.

how you mentioned that my carb may be too rich: If i turn in the mixture screws on my edelbrock a quarter turn i get backfires through the carb, meaning, I think, that it is set, if anything, more lean.

The air/idle mixture screws are for the idle circuit. Once the primary opens even a small amount you are no longer using the idle circuit. Adjust those screws at idle with a vacuum gauge connected to FULL vacuum source to yield the highest vacuum. Re-adjust your curb idle speed after that.

Depending on what carb you are using will determine what other carb adjustments may be required. Edelbrock and Holley have good on-line manuals.