So, timing finally clicked for me, and I thought I had it all nailed down, but turns out, I didn't. I recurved the dizzy with a Mr. Gasket advance curve kit, and am using the lighter silver springs that came in the kit. I have 13 deg of advance timing that comes in at 2,700 rpms. My initial timing, with no vac advance, is 16 deg. With the vac advance, at idle, the timing is 34 deg, so I am getting 18 deg from the vacuum. The problem I am getting is, the vacuum advance never seems to go away. So, in other words, when I spin the motor to 2,700 rpms or more, the timing GAINS another 13 deg on TOP of the 34 degrees it idles at. If I push the rpms much past 2,700, I get pinging. And this isn't even under load. I am using manifold vacuum, on a port on the driver side front of the carb, just above the fuel screw.

In trying to trouble shoot, I started working backwords, putting things back to the way they were before I started playing around with it...I put the vac hose back over to the venturi vac port, on the passenger side, which yields NO vac advance at idle, but keeps my total timing at 34 deg above 2,700 rpms. Also, the timing does a smooth increase, from the base of 16, up to 34, as the rpms climb, rather than the jump I get when running it on manifold vacuum. Problem with the venture vac, however, is the timing is retarded at lower rpms, resulting in hot exhaust, resulting in ruined spark plug boots, even WITH wrapped headers, boot protectors, etc.

Any ideas, thoughts, where did I screw this up?

 

Dial in the mechanical timing with the vacuum advance disconnected and plugged. Then add in the vacuum advance.

 

That's what I did. I disconnected the vac hose from the dizzy can, plugged off the hose, set the initial timing at 16 deg, revved the motor to check my mech advance after doing the recurve, and I get 18 deg mech advance, all in at 2,700rpms. The problem comes when I plug the vacuum hose back into the dizzy, and recheck my mechanical advance. With the vac plugged in, at 2,700rpms, it's reading 45 deg, and it pings past 2,700 rpms.

 

At 34 degrees advance from the mechanical and initial it burns the boots? did you replace the harmonic balancer by chance. according to lars papers you want the vaccum setting on the vaccum advance set 2" hg lower than what the car idles at in gear.

 

When vac is plugged in on Venturi port, I don't get 34 deg idle, I only get 34 deg timing at 2700 rpms. At idle, it stays at 16 deg, and slowly advances to 34 as rpms increase.

 

You're missing lot's of important information here, such as car year, engine, and if it's stock or not. Never heard of a stock engine that specified initial timing at 16°(with no vacuum advance), usually at a specified idle rpm, and could be your problem. A typical stock spec would be more like 8° initial @ 750 rpm idle. If you’re running to much cam for your CR and head flow set up, maybe why you’re needing so much initial advance. Either way, you’re looking for about 33-35° total initial + mechanical at the mentioned 2700 rpm, with no vacuum assist. Vacuum advance is only is only for light throttle highway cruising, and can add another 20°. Keep in mind, vacuum in an unloaded stationary car @ 2700 rpm, is worlds away from driving it loaded, with the carb plates wide open. Vacuum to the advance can will be virtually zero at this point, whether timed port(before the carb plates) or manifold(after the carb plates). Vacuum advance function, is little understood by many, so hopefully this helps a bit.

 

Are you running premium fuel? Might need it. Do you get ping driving the car? You are perfect on initial and centrifugal advance. Sounds like you getting to much vac advance to quick. Check the vacuum and get the right can.
http://www.lbfun.com/warehouse/tech_...ance_Specs.pdf

 

The port on the driver's side front of carb (Q-Jet) is a PORTED vac source. Look for a port coming out of the passenger side of the carb, in the choke mechanism area. That one is manifold vac, and not all Q-Jets have it.
Re-read the timing sticky...
Carter

 

Couple other things to keep in mind. If your engine is modified in any way, you're really needing to re-jet the carb, as could be causing the lean condition. If you're no longer using EGR, you can usually drill the carb port with 1/16" bit to the top of the throttle plates, for a timed vacuum source. Also, if getting a vacuum gauge, may as well get a Mity-Vac hand pump with gauge, as can be used for HVAC system/headlight door diagnosing too. The Silverline set I have, also has a container for brake bleeding.