I have 750 edel. man. choke. and was wondering which way to hook up the vac.Full advance port vac. on the driver side of carb or hook it up to the other port the passenger side of carb. I want as much power and snap as I can off the line and up. It's on a 78 460 with goodies What are the pros and cons of each.Thank you




PSYCHO 1977 F-250 4x4 472cid 4spd., PSYCHO2 19771/2 F-250 4x4 472cid.auto. Pulling Trucks/Race Trucks and goodies to go with them!!!,1987 Mustang GT 5.0 H.O. SNAKEY2. 1989 Mustang LX 5.0 H.O. Spectator Eliminator!
Not worried about gas mileage just performance!!!

 

one is for electronic ignition and one is for points. The instructions tell you which one to plug it into and then plug the other. Just do what the instructions say. doing it backwards will not really help off the line performance, and will hurt fuel economy, so just do it right.

If you don't have the instructions you can get it off their web site.

 

WHAT????????? The passenger side port is for the vacuum advance. The drivers side is manifold vacuum. You never want to run manifold vacuum to the vacuum advance because as soon as you push the throttle, the manifild vac drops which means that the timing will retard when you accelerate which defeats the whole purpose of having an advance in the distributor to start with.
If you have a stock type snorkle aircleaner, you can run the heat flap to the driverside port, or you can just block it off.

 

yes, but if you read the Edelbrock spec sheet and directions it will tell you that one is for electronic ignition and one is for points. Ididn't write it, I am just repeating what Edelbrock says. I dunno why, things just is...

 

Over the years autromobile manufacturers have used both ported and manifold vacuum for their vacuum advance. I prefer to use ported if I can because the idle tends to be better, and my off idle acceleration tends to be snappier.

When you are under light to moderate acceleration, and when you are under cruize conditions, you get full vacuume advance. This gives you the optimum ignition timing for power and econimy. However when you are under harder acceleration, the vacuum signal to the distributer drops, thus causing the timing to fall back to mostly mechanicle timing. This way you will get maximum performance with out pre-ignition or detonation.

In your case, you need to set up your timing by looking at total timing. With your vacuum advance hooked up, and using a timing light, accelerate your engine untill you have reached the maximum amount to timing advance (usually around 3000 RPM). You will want to adjust your total timing around the 42-45 degree range for starters. Once you have this set you can play with manifold or ported vacuum, and also how much total advance you run.

Good Luck!!

Nick from the frozen north
1974 F-250 4X4
soon to be 429
dana 60 front and rear

 

I guess it's not always best to read the directions. I have never had and engine run better on manifold vacuum. And it shouldn't make a hill of beans difference if you have electronic or points, the distibutors both advance the same way.

 

well tell that to Edelbrock. I think they may know a thing or two about this. Some guys may have their reasons for doing things different, but Edelbrock has their reasons to direct their customers to hook things up a certain way too. I think when in doubt, I will follow the directions.

 

good luck then

 

40 -42 degrees timing sounds very high. Most guys are running a max of 38 before they get into detonation. I would suggest 12 -14 initial with a total of 36 -38 in by 3000. But each engine is different so yours may vary.

 

Well, mine runs like crap when I hook mine to direct vacuum. I still don't understand how retarding your timing during acceleration is going to improve performance or economy.This is why it is called a vacuum advance, not a vacuum retard.

 

LX man, what happens to engine vacuum when you put you foot into it? I goes down doesent it? So if your vacuum advance gets less vacuum due to increased load, what happens to the total advance? It goes down.

You have to realize that under increased load, your cylinder pressures and temperatures go up drastically, and so your optimum timing advance must be lower to compensate for this.

During crusing conditions, you can have more advance because your cylinder pressures are lower, as are your cylinder temperatures. Your burning process is also more efficient at this load with increased timing.

There is a lot more scientific fuel combustion chemistry that would just put us all to sleep that states basically the same thing. Do not let the name vacuum advance fool you. I s only a name, not a description of the workings of it.

Nick from the frozen north
1974 F-250 4X4
soon to be 429
dana 60 front and rear

 

How many people run no vacum. With the dist set at full advance say 40 degrees. This is how I was taught to do it when I was involved in dirt track cars. It also happens to be were my 460 seems to run its best. I do beleive that it hurts fuel economy. But thats not what Im after in this truck I expect it to suck gas.

 

If you race your engine, say in oval track or dragracing, thee is no need for a vacuum advance. Most of the time your foot is burried into the floorboards anyways

Nick from the frozen north
1974 F-250 4X4
soon to be 429
dana 60 front and rear

 

thanks phantom ive tried runiing the vac advance at multiple timing settings and i really have found it to run best without maybe i have a bad dist. or something but its kinda lazy with the vac hooked up

 

my 460 does not seem to care much for v/advance either, although i keep my foot in it pretty good, so its not used much anyway