123 Ignition Vacuum Adv, Learn me on some vacuum Options

[nditiz1]

Ok so I'm currently running the 123ignition dist on my 2056 with dual webers. I read the instructions and don't understand the mapping. I also don't know how it all works together. Can someone educate me on the vacuum adv and what curve would be best? As the rpm's increase it creates more vacuum thus creating more adv, but if I already have a curve setup to go from 12 degrees at idle to 28 degrees at 3000+ will the vacuum adv move the timing even higher once it is hooked up and mapped?

[Mark Henry]

On dual weber's you shouldn't run vacuum advance, dual carbs (or ITB's) have a piss poor vacuum signal and will likely only cause you headaches.
The more duration the cam has the worse it gets.

If you really want vacuum advance I would run the vacuum hoses to a central sealed box then to the dizzy. I'd also stick a .023 mig welder tip into the vacuum hose(s) to help even out the pulses.
Likely you'll have to tap the manifolds in a couple of different places and play around to find the best vacuum signal.

I won't be surprised if you end up capping/disabling the vacuum advance.

[72hardtop]

On dual weber's you shouldn't run vacuum advance, dual carbs (or ITB's) have a piss poor vacuum signal and will likely only cause you headaches.
The more duration the cam has the worse it gets.

If you really want vacuum advance I would run the vacuum hoses to a central sealed box then to the dizzy. I'd also stick a .023 mig welder tip into the vacuum hose(s) to help even out the pulses.
Likely you'll have to tap the manifolds in a couple of different places and play around to find the best vacuum signal.

I won't be surprised if you end up capping/disabling the vacuum advance.

Not necessarily.

One must check with a vac gauge first and see.

With my set up a vac gauge showed ~10in of vac when blipping the throttle with 40mm Webers.

You should have 0 vac at idle. If you don't your carbs are not set up right. The vacuum will be right off idle. Most SVDA distributors will start advancing at roughly 3.25in and stop at roughly 8-10in

Pull the vac from only (1 vac port) off the carb (Dual Webers) not two. Doing so will lower the overall vac due to vac signal fighting each other. Install an anti pulse valve as close to the carb port as possible. This will not only smooth the signal but also increase it a bit. Preferably pull from #4 since it's closest to the distributor.

Anti pulse valve:https://vwparts.aircooled.net/Anti-Pulse-Valve-for-Vacuum-Advance-Distributors-p/anti-pulse-valve.htm

Vacuum advance is miles ahead of mechanical only.

Only then can one begin to lean tune the AFR during cruise.

WOT - 12:3 - 13:2
Part throttle - 16:0 - 17:0

Avoid - 14:0 - 15:0 (Deathzone) Highest EGT & CHT's Get above it when on the progression circuit and below it when on the mains.

Load = Throttle position

Part throttle is NOT load. To many folks believe holes in pistons are cause solely by a lean AFR. It isn't. It requires a lean AFR with timing issue (excess usually) combined with LOAD. If ones timing is spot on with an SVDA any load (foot in throttle) will pull the timing back (increasing load) to where it is set at full mechanical. Preferably no more than 28-32*BTDC @3200+rpm's