15 " hg is not bad with a high mileage, and 305 at about 800 rpm. I'd suggest forget the vacuum gauge, set the timing with a timing light, and idle rpm with a tach.
My personel opinion on a quad is I like them. I'm not raggin on the 305.

 

Ok cool thanks for the help

What would I need, to use a timing light? Like a tab or/& balancer with the degrees on it?

 

Timing light and a tach/dwell. Both should be around 20 bucks

 

Cool, thanks again

 

I think the Hg should be higher, you might do a Compression Test on it.

 

Since I'm waiting for my mixture screw tool to arrive I was messing with my vacuum gauge, I hooked the gauge up and covered the primary choke plate briefly with my hand, the vacuum rises from 18-19 to a little past 20 inches and it idles higher. Would this indicate that I'm running lean?

the car is from nevada and im in illinios so there could be a huge difference in the mixture because of the temperature and elevation difference

 

Well, the increase in idle speed would drive your vacuum up more, so, that's not the issue. The fact that it happens when you choke it down, is. I'll revert to my original recommendation about checking the system for integrity. That usually indicates you have a leak.

But in addition to that, and given my propensity for Testing, I'll further recommend a Fuel Ratio Test as well. That should settle any question about intentional settings or specific parts related to altitude.

Make sure your system is tight FIRST !

 

Very informative thanks, unfortunately I don't have a compression tester or an air/fuel gauge at the moment

I know I can grab a cheap compression tester but afr gauges are pretty expensive, do you know of another way to test the a/f ratio without having to buy a wideband gauge?

 

Compression guage are not too exspensive. The reference to low "hg is normally a good engine at 700-800 rpm will run about 20-21 "hg.
I have a 455 olds with 170K on it, I cannot get more than 18-19 on it. Not "worn out" but some blowby.

 

Well that's good to hear, I thought I should be getting a much higher reading