Thanks for the question.
As I have said before, in a full blowen drag racing application were the car is towed to the track the vac. advance is not as important, many guys run with out it at the track. However on the street you really can't live without it and here are the reasons.
Timing! Thats right its all about the timing.
The vac advance unit provides a number of benifits first better gas mileage, better driveability under part throttle driving, and better starting. How you say?
By being able to set your initial timing at 12 degrees  instead of 20+ degrees of timing like someone suggested, your cars starting system will not burn up trying to start the car with too much initial timing. Too much initial timing can actually cause the engine to kick back the engine as it is turning over and damage the starter, battery etc.
Second the dist. does have a certain amount of mechanical advance built in for when you set total timing, say 36 degrees. So what does the vac advance unit do.
When you hook up the line after you have set total timing your initial timing will be about 20+ degrees, or similar to what some set their timing at without a vac unit.
Its the same more or less without causing possible starting system problems.
At highway speed when the mechanical advance unit and the vac. unit connected you will have a total timing of about 46 degrees at cruise speed. How? 36 total mechanical and about 10-12 degrees of vac advance timing.
Sounds like to much? Its not because when you are cruising there is no real load on the engine and you want maximum timing for fuel economy.
What happens when you accelerate quickly, the vac. in the engine drops and your advance unit loses its vac. signal under full throttle conditions. You end up with 36 degrees of timing that you had previously set. Right were it should be for full throttle acceleration this is so you do not get any pinging or pre-ignition.
Under part throttle conditions you will have some mechanical and some vac. timing for again better overall drivability. So you see for a street car you really can't live without a vac. advance unit.
35 yrs. ago I too fooled with disconnecting the vac. unit on a 383 Road Runner, It seemed to drive o.k. except it cost me about 8 miles per gallon. Lesson learned, and when I went through school and became a Class A Mechanic I soon understood why it was important to run with the vac. unit on the dist.
Hope this helps, if you have any other questions feel free to e-mail me at 67mopar@sympatico.ca.
If I can't answer a question I will get you connected to the right people who can.  

Dr M,

This makes sense for sure, thanks for the note and the private email.  While I'm a degreed electrical engineer from quite some time ago, and I'm into my "bucket list" with the cuda in my 47th year of life, I've got dozens of questions from the EE in me and I just have to know how this stuff works!  I truly appreciate the responses and I hope I don't bury you in too many *newbie stupid* questions...

One last question, the shop manual says to set initial timing at 5deg BTDC for an auto at idle w/vacuum plugged...I tried this and it runs like crap and hard as hell to start cold and warm(ok, another point here is that the choke is disconnected by the prior owner... wide open so the gas mix is too lean at cold start and would explain cold but not warm start).  Setting at 12deg by experimentation seems to work great at idle...with no knock or ping this seems to be ok. Why won't 5 deg BTC work even when engine is warm?  I would have expected a warm engine to be ok with this setting due to burn working ok at idle rpm's (in other words the mix has enough time to burn efficiently at low rpm's at pretty near TDC spark fire).  It starts but sure is hard as hell to start when warm unlike at 12BTDC timing.  The mystery to me is why 5 deg is no good as the shop manual says...  I did find it interesting in an earlier posting that you had suggested to another to start at 12 deg and had not seen that as a standard start point on any engine in a few books I'd looked at.  Where did that come from for you?
Thanks again!  

From yrs. of working on street strip cars I discovered that book is O.K. for a general rule, however when it comes to muscle cars they always like timing.
So I try to start off with the most initial timing without causing starting or pinging problems.
I also go one step further with the vac. advance units. After setting initial and total timing, I will see were my total timing is with the vac advance hooked up.
This is important with a high performance engine so you do not have to much total timing.
My 1974 360 engine had a total of 58 degrees which was way to much. The dist. came out of a my 74 smog motor which would have been a very low comp. engine and would explain how the factory could get away with so much total timing.
Anyway, to correct this I got an allen key, installed it inside the small vac. advance hole which is adjustable. I turned the key counter clockwise 4 or 5 turns, rechecked and set the total timing with the vac. line on until I had a ready of 48 degrees.
Perfect for cruising on the hwy. and the car with 4.30 gears and a tall tire manages to get 18 mpg. and still run 12.6's in the quarter.
So I have the best of both worlds, a super high performance engine that gets reasonable fuel economy in a 40 yr. old car, its a blast to drive, all this in a small block that runs big block numbers in the quarter mile. How?
 Total Package, every part of the motor and vehicle need to compliment each other.
This is were most guys don't get it. They almost always over do one thing like the cam, and then end up trying to fix the problem by giving the vehicle to much initial timing. I consider this approach a bandage and not a fix.
So when you start a project you need to research and ask a 1000 questions to get it right the first time. That way you will save a ton of money and frustration.  

Thanks for all the replies and information.

When I built this engine I was aware of the temptetion to go too big, that was the reason I chose to go with a package from Edelbrock instead of trying to figure all out myself.

I have now set the initial timing to 20 degrees. By doing that I was able to decreas the throttle blade opening to 0.02-0.025". I thought that it would help cause I was reading in my Holley book that the throttle blades shouldn't be open more than 0.04-0.06". But still no increase in idling rpm when turning the mix screws...? I have now opened the mixing screws 1-1.5 turns.

The car now idles ok at 1100 rpm but when I change it to D the idle drops to 800 rpm and the idle becomes rough.

Still no low end power. The converter (2500 stall) doesn't stall more than 1500 rpm when I try to stall it using the brakes.

The spark plugs looks ok (as far as I can tell). I took the carb apart and everthing looks like it should according to Edelbrock instructions. How should I tune the carburator? Edelbrock Perf. 600 cfm.


Thanks again.

BR
Kristoffer  

I would be tempted to install the cam 4 degrees advance, this will make a noted improvement but don't expect miracles.
As far as the timing goes I give up, I have given you all the reasons to reinstall the vac. advance unit but you clearly are not interested in a Class A tec.'s opinion.  

drmopar:
I would be tempted to install the cam 4 degrees advance, this will make a noted improvement but don't expect miracles.
As far as the timing goes I give up, I have given you all the reasons to reinstall the vac. advance unit but you clearly are not interested in a Class A tec.'s opinion.

Don't give up on me just yet...  

My budget is now down to zero on this project and I would like to try everything with what I have and I have a non vac. distributor... Maybe I need to buy a new distributor and carburator and camshaft but not until I tried everything I can with what I have.

I am pulling the engine this winter and I will consider install the cam 4* advance.

I appriciate all your inputs.

BR
Kristoffer  

MR dr. You've given the same reason over a million times now and it still equals the same thing I already said =gas mileage and nothing more cause guess what If you think vac advance is gonna raise to the desired 20* after started your wrong and not only in that way but in recommending it to someone pretty & much misinforming them.
See even if you got the vac advance to raise the initial timing from 12* to 20*+ @ idle you would have to loosen the vac canister up [allen wrench] so much that you'd end up with way to much vac advance [52*+] and on an already raged edge comp wise engine, dumb.  
DR. if you really read what I posted on how to go about raising the initial you would know that the idea is to raise the initial till the motor won't start or [starter has trouble turning it] then back it of a couple of degrees so that it WILL start with no stress on the starter  [engine fighting the stater] note this setting=Thats where your initial wants to be, Then limit the mech advance to what ever the engine likes for total 30*,32*,34*,ect
BTW in [general drag racing] you retard the timing to start it then lock it down at the required amount of total timing, so there is no curve OR VAC ADVANCE.  

SWEDEFISH I recommended the raising of the initial in order to liven up the bottom end However You really don't have enough gear. 3.73 should be the minimum in your case. 2 things since your taking to this gas mileage thing [which is fine it's your deal] advancing the cam will bring the bottom end up with sacrifice to the top end and gas mileage [earlier intake opening] I also run 4* adv with a .528 solid but I don't care about gas mileage. Dual plane intake would help bottom end torque a lil .
The edlebreak carb is ok but I would have gone with the 750DP holley and in order to see if the blade are in the wrong position you will need to take the carb off flip it over and see where they are in relation to the idle slots[and get a edlebroke book for your edlebroke carb!  

Look dr. you don't have to have certification to give good advise and when you reference class a are you talking about your drivers license?
Just so every body knows, when a guy starts going on about his credentials It's cause his argument doesn't hold water and he's run out of pitches to throw at you.
OH and especially don't listen to ASE guy's they are the first ones to *** things up.
DR. not a personal attack but come on you know vac advance is a gas mileage thing and should have nothing to do with an engines ability to idle & run right.
ARE YOU A TUNER? OR just a mechanic?
SWEDEFISH What is your manifold vac reading @ idle car in gear with e-brake on? If you have a pro billet then put the large black bushing into it and install 1 blue spring amd 1 silver spring then set it to 34*full advance should come in around 2000 rpm.  

I appriciate all the inputs. Thanks.

I have now set the initial timing to 22*. I think I can advance it even more since I can't hear any ping and so far no starting problems. We have 95/98/99 octane pump gas in Sweden so maybe I can have more than 34* full advance?

Change gear is something I'd rather not do, if I don't really have to. I like to cruise at a decent rpm. However my friend has got a 3,90 he wants to sell...

I run a dual plane intake now, Edelbrock Performer RPM air-gap.

I took the carb top off. The blades are open about 0.02-0.25. I was able to close them a bit more tonight (it is midnight now in Sweden). I also raised the floaters a little bit and changed the seting of the power valve in order to get more fuel.
It still idle rough. I never had time to take the car for a spin tonight. And I never had time to try my Holley 700 DP. I don't have a Edelbrock book but I do have the Video and some instructions that I printed from Edelbrock homepage.
I did check my vacuum. between 5-7! It varied alot! Strange or? Do I have a intake leak maybe? Might this be what is causing all the idle problems as well as lack of power?
I hope I will have the time tomorrow to check for leaks.

Thanks again.

BR
Kristoffer  

Cool.
1st on the timing thing set the total where ever the car runs best, 34* was just a starting point, It might run better at 30* who knows.  
Now when you get the 700 DP on there first put a 3.5 power valve in it or half of what ever the vacuum reading is @ idle in gear.
The idle vac reading will bounce a lil with an aggressive cam, but if it's really fluttering it could be a leak, put your hand over the carb while idling blocking the air it should kill the engine, if not vac leak . spray w-d or water [mist] around intake if the idle drops/lowers for a second =vac leak.
Did you actually degree the cam in or just put it straight up?
Good to hear you experiment and find out what works and doesn't work, and what would work but only in conjunction with...well you get the picture.  

The needle was really fluttering. I will check for leaks.
I installed the cam straight up, I hope!   I had some difficulties installing the cam, but I think I managed to install it straight up...    

Hey Justin I thought we were going to agree to disagree? And yea I do get 22 degrees of timing with my vac. advance connected at idle, and 48 degrees with the vac. connected at 3000 rpm, and that why I have great drivabilty, performance and fuel economy.
Remember its all in the package we talked about,   pictures & e.t.'s speak a 1000 words.  

Hey, I've tested this and thats what I know.
Different people, different experiences.
Your et doesn't make you a know it all anyways so lighten up.
Basically I'm agreeing to disagree.
Mainly, lets not side track from his real problem, which is not the vac adv /mileage bit. Once he's figured how much initial he can use he can then find out what total timing his motor likes and get down the road already.
Besides he doesn't have a vac advance on his distributor.  

Your might be right, but I believe he probably still has his old vac. advance dist. and by reinstalling it and tuning it as recommended he can have the best of both worlds.
It would make sense if it is a true street car.  

For once I agree with 3404dp.

You need to bring that initial advance curve up to 20* and your total around 34-36*

I didnt see what gears and tires you were running but I would like to see a 391 gear and 26" tall tire ot 410s with a 28" tire.

For a carb either a 700 or 750 double pumper.

Dont worry about the vacuum advance. With a double pumper and 410s gas millage isnt going to be great anyways, LOL  

Welcome to my world.lol