Eliminating vacuum advance

[daytonalo]

472 hemi , 600hp , 373 rear , tko 600

[Ghoste]

If vacuum advance is mainly improving mileage during a cruise condition, well, you know where I'm goin'.

[daytonalo]

I agree , all the above. My concern is the crane digital box has multiple curve all with a max advance of 34 degrees around 2500 . Again how will the vacuum advance operate with this system , and wont it give me more total advance ?

[Ghoste]

Not if you adjust it to only pull in under the higher vacuum load.  If you are using that overdrive trans, then you should see a lower rpm during cruise (high vacuum) conditions. 
Do you already have a distributor picked out for this?

[daytonalo]

I have a stock dist with a crane conversion , I want it stock appearing

[Ghoste]

If it were me personally, with a setup like it sounds you are going to have I would run a vacuum line to the distributor but up there at the carb I would block it off and just dispense with it's participation altogether.  It sounds like performance is the number one consideration in your case.

[daytonalo]

I still want good highway economy

[dave571]

Depending on build, the vac advance won't make much difference to economy, if any, much as neil has described.  A 509 cammed 440 in a B body will make no better economy with vacuum advance.  A stock cammed unit  will.

As for the ported/manifold debate, this comes up often, but the answer is always ported.
The manuals say so, and so does all know timing theory.  I don't know why the guys at edelbrock think the install of thier carb should affect the way a motor is timed, but it doesn't.  Cam and compression, are much bigger factors.

The vacuum advance IS for economy only.  If properly installed, even the guys who run it, will notice NO performance difference at all with it disconnected.  If there is a difference, it wasn't right to begin with.

The thing that seems to not be mentioned enough in this thread is total timing.   

The best way to set ignition timing BAR NONE, is to set the total mechanical timing.  On most open headed cars, 34-36 degrees. with the vacuum off, at whatever rpm your timing is all in at.

If that makes your initial too low, then you need to shorten your advance slots so you can boost the initial as required. 
Too high, and the curve is too short.

[deputycrawford]

Dave 571. For just having 2 posts on this site, and no credibility what so ever, I agree with absolutely everything you posted. Thats a good continuation to the reliability of the information on this site. Welcome, and I hope we can assist you in the future as well. There are many here with much experience. Oh, and we all goof around a bit too.

[Chryco Psycho]

Depending on build, the vac advance won't make much difference to economy, if any, much as neil has described.  A 509 cammed 440 in a B body will make no better economy with vacuum advance.  A stock cammed unit  will.

As for the ported/manifold debate, this comes up often, but the answer is always ported.
The manuals say so, and so does all know timing theory.  I don't know why the guys at edelbrock think the install of thier carb should affect the way a motor is timed, but it doesn't.  Cam and compression, are much bigger factors.

The vacuum advance IS for economy only.  If properly installed, even the guys who run it, will notice NO performance difference at all with it disconnected.  If there is a difference, it wasn't right to begin with.

The thing that seems to not be mentioned enough in this thread is total timing.   

The best way to set ignition timing BAR NONE, is to set the total mechanical timing.  On most open headed cars, 34-36 degrees. with the vacuum off, at whatever rpm your timing is all in at.

If that makes your initial too low, then you need to shorten your advance slots so you can boost the initial as required. 
Too high, and the curve is too short.

I agree
usually you will see a performance Gain with the vacuum disconnected as ti will allow more initial advance at idle where ti really helps

[Chryco Psycho]

Dave 571 is Knowledgable

[Duey]

Dave 571 is Knowledgable

I did what Dave (and Ron and Neil) recommends about shortening the slots in the distributor (with my MIG welder) so my timing is 16* at idle and hits 37-38* by 2800-3000.  Once I get all the new bits on the motor, we'll see how it like it.

Cheers,
Duey

[dave571]

Dave 571. For just having 2 posts on this site, and no credibility what so ever, I agree with absolutely everything you posted. Thats a good continuation to the reliability of the information on this site. Welcome, and I hope we can assist you in the future as well. There are many here with much experience. Oh, and we all goof around a bit too.

Thanks man. 
This one is post 5, so I'm working my way up...LOL

Thanks to Neil for the kudos too.

[Chryco Psycho]

you are welcome Dave , I know you have spent a  lot of years working on these older Mopars as well