Techical Discussions => Tech- - Engine => Topic started by: attkrlufy on April 28, 2008, 07:25:22 AM

Title: Vacuum vs. digital advance
Post by: attkrlufy on April 28, 2008, 07:25:22 AM
Hi guys.  I'm new here and I'm hoping someone can help me out.  I'm the proud owner of a '79 New Yorker w/ a 360 4v.  I'm in the middle of deciding what to do with my 1) Tired, old, leaky Thermoquad and 2) Screwy Lean-Burn ignition system and I'm looking for some help.

Regarding the ignition system, there seems to be two ways to go about this: I can get either A) Mopar electric ignition w/ vacuum advance, or B) Aftermarket system with digital advance (MSD?).

So here's the question:

"If they both do the same job, which system should I get?"

I'm leaning toward an MSD-equivalent system because they seem to have fewer moving parts and (in my book) fewer parts = less things to break.  How's my logic here?  (In case you haven't guessed, I don't really know much about this stuff.)
Or, another way of putting it would be: Is there any reason I shouldn't get a system which has pre-set digital advance curves?  I don't care so much about "stock" as I do reliability and efficiency.

I've asked this question over at the Allpar forums but no one's answering it.  Maybe I'm not clear, I dunno.  ( (

Title: Vacuum vs. digital advance
Post by: Steve on April 28, 2008, 08:06:07 AM
There is a third option
Get a Holley Commander 950 TBI EFI system and go with the electronic advance it features.  I did that on a 360 and it worked great, when the rest of the car did.  It improved the mileage and the economy.  When the rest of the car worked right that is. . .
The only major mod you will need to do is add a return line to the tank (Use the old fuel line) and bring back a 3/8 feed line.
If you don't want to go to that much trouble, then I would just go with a "tuned" distributor with a vacuum advance, Mopar Ignition and Edelbrock.  Less expensive and will do wonders for you
[color=#ffff00 size=7]WELCOME![/color]
Title: Vacuum vs. digital advance
Post by: Snotty on April 28, 2008, 10:18:02 AM
Now there's a car you don't see everyday!  Welcome!
The answer to what you are asking depends on where you live and the local smog laws.  For instance, if you are in California you can "legally" change the carb to a 50 State approved alternative (available through Summit) but you can't touch the ignition.  Again, legally.  I had a '79 Cordoba 360 4bbl; I broke off the idle screw limiters, richened the carb up and installed a MP Ignition.  But, when it was needed to be smog checked, I reinstalled the lean-burn and leaned out the carb again.
If smog laws are not a problem for you, what Steve suggested is a great alternative but is also expensive.
I would suggest a nice Edelbrock AVS carb and intake and the MP Ignition.  You will notice a great improvement in power and economy.  
Title: Vacuum vs. digital advance
Post by: attkrlufy on April 30, 2008, 04:21:52 PM

Thanks for the warm welcome, guys.  I appreciate it.  (

The TBI system sounds nice - but I think it's a little too much $$ for me right now.  Truth be told, I didn't even KNOW such a product existed.  Now it's got me thinking that at some point in the future I might be able to get an MPI injected Magnum 360 under the hood.  But for now, I think I'll stick to carburetion.

So you think a modern spark-control system is better than a vacuum-advance one.  Can I ask why you think that?  Is there something about the older Mopar system that you want to avoid when compared to the newer products out there?

You'd also go with Edelbrock over Holley, right?  Is there a reason?  I think Holley makes a direct replacement for my Thermoquad: (  I'm not sure Edelbrock make a Thermoquad replacement.  I think the 650cfm Thunder AVS is the closest match - but isn't that a square bore carb?  Won't that require an adapter to fit my intake?  Then there's emissions.......

I ask because I really am looking for the closest automotive equivalent to "plug-n-play".  I don't want to have to tune this thing too much or deal with spacers, manual chokes, etc.  I want this car to be a "driver" that I take to the occasional show.  I'll figure out "tuning" it later - for now I just want it to work properly and with minimal fuss.

I's a New Yorker.  I'm not planning to race anyone in it.  (

attkrlufy2008-04-30 21:22:56
Title: Vacuum vs. digital advance
Post by: Steve on April 30, 2008, 04:35:43 PM
I did one of those already.  Although, I would think you might be the first in a 79 body.
Let me introduce you to Polaraco (
This is a 5.2 and a 518 stuffed in a 72 Polara
I'll tell you everything you need to know.
You need a full running truck and a factory service manual for it.  You'll need the complete under hood harness,  throttle cable, all that stuff.  It would be wiser if change the trans with it.  See if you can find a wrecked Dakota.  The 500 trans will fit right in the tunnel, but the trans mount will be a problem.  Need to make one.
I used a 92 D150.  92 and 93 are the easiest.  The rest require more of the body to be attached.  ODP2 will require 2 O2 sensors.  94 on up, but they don't require a return line
Title: Vacuum vs. digital advance
Post by: Steve on April 30, 2008, 04:41:00 PM
It's all personal preference
I do not like Holley at all.  When they go bad, they are bad.
I suggest Edelbrock.  Maybe a 600 CFM will do the trick.  Get one with an electric choke.  The wire is already there on yours.  They're a little less than the Holley and allot less hassle.
If you buy the Edelbrock, there are tuning kits for them.  The kit is about $35.00.  You'll be able to tune it for either max economy or performance.  Also, DON'T for get the Mopar Throttle Adaptor
Title: Vacuum vs. digital advance
Post by: Butch Houghton on May 07, 2008, 07:10:25 AM
But....the eddy will Not bolt onto the Thermoquad intake...without an adaptor plate.    that Holley will & yes I used one to replace a T-quad & it ran fine.    I traded it later to another friend to replace the Quadrajet on his 88 360 PU.  

Only correct way to use the Edelbrock is to change intakes.    Eddy's are a square flange not spread-bores.     nothing wrong with either carb,  they all have their " Quirks".    

There's nothing wrong with Thermoquads either,   When they're right they run great.    The only thing you don't have on a Leanburn Thermoquad is the correct vacuum port for Vacuum advance if I remember right,  They can be modified for that though,  Demosizzler is the guy for that stuff.

The simplest Ignition is the Mp Conversion kit.  The Orange Ign boxes that come with them are prone to failure nowadays but the easy cure is a good Partshouse Ign box from Napa.

Or....go buy a Partshouse Electronic distributor,  get just the harness from Mp &go buy the Ign box local &save a bit on the whole thing.  

The Chrysler ignition is pretty much dead reliable.

It really just depends on what you want to spend.


Title: Vacuum vs. digital advance
Post by: attkrlufy on May 18, 2008, 07:48:40 AM
Thanks for the advice on this matter, guys.  I think I'm going to go with this MSD unit: (

It seems the simplest and most durable way to replace my lean-burn.

Do I understand this product correctly?  There's nothing else I need to add to the system - just the distributor.  It sounds a little weird - I always thought there had to be an external spark box in these add-on systems....but maybe not.

Anyone use this or know of someone who has used it?

Title: Vacuum vs. digital advance
Post by: Bill Mounteer on May 18, 2008, 06:57:15 PM
Oh dear, I'm confused again! (

I've been thinking of buying a Mopar Performance distributor, with vacuum advance, and then either use the Mopar Performace control box or the one MSD sells for about $150.

Now I see the new fancy looking E-curve distributor.

I guess my first question is the only real claim to fame for these E-curve units is that they are plug and play and no extra boxes and wires to worry about? 

I'm a correct to assume the digital controls would be basically the same for both e-curve and bolt it on the firewall electronic box?

I'm interested in the new e-curve, but I wonder how well the electronics will survive sitting on top of a hot engine, especially after shutdown and heat soak really sets in on really hot days.

Title: Vacuum vs. digital advance
Post by: Jacques on May 20, 2008, 02:28:36 AM
The E-curve looks nice, but its not really a proven toy yet regarding reliability and performance (and only available for smallblocks.)
I'd rather go for the MSD Pro-billet ready to run dizzy instead, with the optional vacuum advance. No additional parst needed, and the option remains to upgrade later on to a hot ignition box.
Or if you want a hotter spark, a plain Probillet diz with the MSD-6 box.