Yet another side draft question
 

So I've been searching for a while and come up with nothing.

I was wondering how exactly you run vac advance for the dizzy on a side draft set up. I have a DHLA 48 on a full racingbeat intake (upper and lower). It has the vac for the brake booster but nothing as far as timing vac.

So is it necessary to run vac advance or is that something you don't need without the Nikki? (seems like it wouldnt matter, but just checking)

You could always just tap one of the "upper" runners and put a barb fitting on it, similar to how guys tap the Racing Beat manifolds for OMP or Nitrous. Though I'm not sure w/ tapping a single runner whether it would pull a constant enough vacuum instead of a pulsating one.

I was wondering the same thing myself. That and I have a feeling I would end up trashing an intake as I tend to be that lucky.

Racing Beat instructions say not to use the vacuum advance.

http://www.gruntled.com/Dellorto/13BInstructions.html

Lock the timing - don't use the Vac advance.

You can leave the vacuum advance off and just run mechanical advance, but don't lock the timing on an NA motor.

you can't just tap the manifold and run a vacuum line. The nikki had vacuum advance coming from a ported source that sees little vacuum at idle and increases as RPM raises. If you run it off an intake runner you will be seeing full advance at idle and as soon as you open the throttle you'll drop to zero vacuum advance... not exactly ideal.

You can leave the vacuum line off of the canister (do NOT cap it!) and run purely mechanical advance, at a slight hit in fuel economy.

But to say to never run locked timing on an N/A is just plain... retarded. <doctorevil> I had a lot of fun with timing locked at ~22 degrees on a stockport.

Bridge ports don't like locked timing, they don't idle well unless you can retard the timing at idle, but stock ports and street ports can use the additional low-end bolstering that you get with running full advance all the time.

What happens if you cap it?

when you say run mechanical advance, what does that mean as far as set up to do so?

It is possible that heat can cause the air to expand and find its way out of the canister, and later when it re-contracts, pull the canister under vacuum and change your ignition timing.

Maybe kinda thin as far as scenarios goes, but there's absolutely nothing hurt by leaving it UNcapped, so why take the chance?

The distributors have vacuum and mechanical advance. To run mechanical-only just means that you're not using the vacuum cans. Simple. Just set everything up as normal.

I've gotten used distributors that had been capped by a previous owner. First thing I do is rip those suckers off.

Thanks for the response.

hey man getting the 12a side draft going? Don't use the vacuum advance, the dizzy has a mechanical advance as well as the vacuum. Don't cap the the nipples on the advance diaphragms. If you have a clamp on wire type (inductive) timing light you can watch where the mechanical advance happens rpm wise and how far it advances. The dizzy advances 20 degrees total so set total advance by revving to or past the point where full advance is achieved, generally around 4000rpm. If your mechanical advanced is working right, if you set timing say at 22 degrees total advance you would see 2 degrees advanced at idle.

Mostly gathering parts together now. Car is looking like this

http://sphotos.ak.fbcdn.net/hphotos-..._3003707_n.jpg

till the spring though =(

Not much progress when I cant get to the car or drive it around.

Theres a big debate about using manifold vacuum as a source for the
vacuum advance. So it pulls full advance at idle, once you step on the gas it
acts like any other vacuum advance. It does help make the Dell feel more
peppy at low rpms and does help fuel economy slightly. I used it for a long
time on my Dell and it was nice. I recently stopped using it since I redid my
ignition because I decided I didn't need it as much.

I say try both ways and see how it works for you. I just teed the line at the
RB intake where the brake booster gets vacuum ( which is off the rear runner ).

The problem with using manifold vacuum for a vacuum source is that, when you come off-idle, vacuum goes away and therefore so does ignition timing. You end up with a big off-idle flat spot.

With ported vacuum, you have zero vacuum at idle. The vacuum port only gets uncovered just off-idle. Net result is you get a smooth idle, and when you open the throttle, a nice surge of ignition advance comes in.

A lot of people who don't understand this basic fact will try all sorts of weird things to try to get more accelerator pump action out of the Nikki when the problem is that they don't have the ignition timing set up very well, because they're afraid of vacuum hoses or something.

its just a series of tubes.....

heh

For certain don't use the vacuum advance. Vacuum is being pulled by the engine trying to suck air past the throttle plates when at idle which, also pulls full advance at idle. When you blip the throttle as peejay stated vacuum drops your timing goes from full advance retarding back to no advance then the mechanical advance takes over as you keep revving, exactly what you don't want to happen. You want the timing to advance as your engines rpms increase. I had my side draft setup with the vacuum advance hooked up and watched what the timing did with my inductive timing light. I set the leading timing at 0 degrees at idle then blipped the throttle which caused timing to drop atdc then come back around. I removed the vacuum lines to the dizzy set timing at full advance by revving to 4000rpm set timing at 22 degrees btdc then let the car fall back to idle where my timing rests at 2 degrees btdc which i believe is on the safe side. It also got rid of the nasty stumble off idle.