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I don't, yet. Waiting on delivery of this.

Key to know: there is a difference between the vacuum advance takeoff on a carb—which if you're running IDFs is that long post with the screw in it facing outboard—and the manifold vacuum required for the Black Box's MAP [Manifold Absolute Pressure] sensor. Those are tiny screws on the bottom of the carb and there's no simple way to get them hooked to vacuum lines.

The port circled in red should work with the Magnaspark. T them together from both carbs and rock on. Those little screws inboard of the idle mixture screws  need weird M5 threads. Those ports are completely below the throttle plates. That's what you need for MAP to work right.

The $50 CP Performance kit obviates the need to either

A. drill out those little screws and solder or epoxy some tubes to them; or

B. drill small holes in the manifolds and solder or epoxy tubes to them.

For me it was a close call. If I had an extra set of those little vacuum port screws I'd have gotten after it with the drill.

@DannyP posted:

@edsnova get some 7/32" brass tubing and a 5mm die. Screw them in with a bit of RTV and you're done. If I was going to use carbs I'd do it that way. But honestly a TPS works just as well for load sensing advance adjustment. That is if the black box allows that.

Be ready to tweak your throttle linkage if using the CB vacuum kit.

It doesn't. It would be great if it did, but no.

I ran a Black Box on my twin-plug engine and am an enormous fan. The interface with the computer is archaic, but the digital advance works fabulously.

Regarding the MAP vacuum load sensor - it's neat, but certainly not required. I'd never let an inability to get vacuum stop me from using the box. As a matter of fact, you'll do a lot better just setting up the curve without any vacuum advance until you get the hang of it. Trying to map for load on your first time out is a bit like drinking from a firehose.

Even if you never use the vacuum, your spark will be 10x more accurate and infinitely more adjustable than with any Chinese distributor.

I did and it's installed. I get my ECU MAP readings off the kit, and the fuel pressure regulator is also attached. I'm not using the MAP readings in the ECU yet, I've got TPS for load on both fuel(called Alpha-N) and spark.

I'll add a secondary fuel curve later for MAP. Probably much later.

The CB throttle bodies have a larger connector that I'm using for idle air control(warmup).

@edsnova posted:

I don't, yet. Waiting on delivery of this.

Key to know: there is a difference between the vacuum advance takeoff on a carb—which if you're running IDFs is that long post with the screw in it facing outboard—and the manifold vacuum required for the Black Box's MAP [Manifold Absolute Pressure] sensor. Those are tiny screws on the bottom of the carb and there's no simple way to get them hooked to vacuum lines.

The port circled in red should work with the Magnaspark. T them together from both carbs and rock on. Those little screws inboard of the idle mixture screws  need weird M5 threads. Those ports are completely below the throttle plates. That's what you need for MAP to work right.

The $50 CP Performance kit obviates the need to either

A. drill out those little screws and solder or epoxy some tubes to them; or

B. drill small holes in the manifolds and solder or epoxy tubes to them.

For me it was a close call. If I had an extra set of those little vacuum port screws I'd have gotten after it with the drill.

The threads are 4 x 0.70mm. And the threads measure about 0.1540" O.D.(3.91mm), so a 5/32"(0.15625") O.D. tube would work great along with the correct die. Brass threads easily, and you can get brass tubing at any hobby shop, Hobby Lobby, model train shop(are there any?) or online. Thread dies are available as well, and no harm will come to your carbs LOL!

https://www.amazon.com/Metric-...617384380&sr=8-1

https://www.amazon.com/PRECISI...aps%2C208&sr=8-3

Last edited by DannyP
@DannyP posted:

I did and it's installed. I get my ECU MAP readings off the kit, and the fuel pressure regulator is also attached. I'm not using the MAP readings in the ECU yet, I've got TPS for load on both fuel(called Alpha-N) and spark.

I'll add a secondary fuel curve later for MAP. Probably much later.

The CB throttle bodies have a larger connector that I'm using for idle air control(warmup).

@DannyP how is it running so far? You like it? Do you miss carb sound?

Go to the CB Performance website and then go to the Black Box item. There's an installation manual link that will tell you about wiring.

If you do this, you will lock out all mechanical advance in the distributor - that's the box's job. The box uses the pick-up in your distributor (points or module), then sends a signal to the box, which uses RPM (and vacuum, if connected) to advance the spark as needed. It sends a signal to the coil, which fires at the appropriate time, and sends the spark to the rotor, which gets distributed (hence the name "distributor") to the appropriate spark plug.

The upside is that it's fully adjustable and can use any locked out distributor. The downside is that it still uses the tiny distributor pickup and the 1920s tech distributor cap and rotor.

It's a nice bit of kit for those who don't want to go all the way to crank-fire and wasted spark.

I agree somewhat. I had Megajolt for years, since 2008. It used a laptop and a serial connection. Once my map was sorted I didn't need to ever touch it.

I'm a tinkerer, so I kept tweaking and adjusting the map over the years, adding in temperature compensation(more advance around idle cold) with a head temp sensor.

But honestly I didn't need to keep tweaking it, the map stayed 95% the same as a month after installation.

I do have bluetooth connectivity on my Speeduino ECU to both my laptop and my phone. It is VERY convenient to easily connect by either Tunerstudio(laptop) or MSdroid(phone). But EFI is WAY more complicated than just an ignition map. And it's definitely easier to adjust on a laptop rather than the phone, but again, that's EFI not ignition.

When I was looking at dizzy options, someone (John at AC?? Ed, the distributor guy??) told me that a single port on dual downdraft carbs didn't produce enough vacuum to properly run a vacuum advance distributor. Running my 4 gauge manometer off the vacuum ports on my Dellortos would tend to corroborate that (they won't. The vacuum generated is so low it can't indicate anything but the most rudimentary sync)

Running off the T might, I don't know. IIRC, OEM SVDA carbs take vacuum off the insulator plate between the carb and the manifold, drawing vacuum from all 4 cylinders.

In the end, I bought a German 009 that Ed rebuilt for me instead.

@R Thorpe

"Hey guys can I pick up vacuum for a dizzy or box by teeing off the balance tube that runs between the carb manifolds?"

Sure.  That would actually be just about perfect.

Actually, just to clarify: yes for the black box, no for a distributor.

Vacuum advance for distributors is "port vacuum"-- otherwise, you'd have full advance at idle. The black box takes manifold vacuum.

Last edited by Stan Galat
@Stan Galat posted:

Actually, just to clarify: yes for the black box, no for a distributor.

Vacuum advance for distributors is "port vacuum"-- otherwise, you'd have full advance at idle. The black box takes manifold vacuum.

Exactly. For distributors there are specific ports on the carb that sit just-so with respect to the throttle plate. Just above but not too far above the throttle plate. No advance(vacuum) at idle, or large throttle opening, but some at slight throttle: just off idle and cruising only.

Manifold vacuum can be used electronically to make a curve for ALL throttle positions.

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