Vacuum Advance Distributor...Anybody Using One On A 1915???

Just wondering if anyone out there is using a Vacuum Advance Distributor on ther 1915 Type 1 or similar engine. The guy at Lowbugget.com just about has me convinced that I need one, but I thought I would ask before I plop down the $$$.
I apologize for all the posts today. I guess I'm still a "newbee" with lots of questions.
Troy

Troy,

Having a vacuum advance distributor is actually a good thing. The Bosch 009 mechanical advance has its drawbacks in that all of the advance is introduced at about 2,500 to 3,000 RPM's. Often times, mechanical distributors can cause a small stumble as you're accelerating through the gears but, they don't require vacuum which is sometimes difficult to obtain from a dual carb engine..

The vacuum advance distributor has it's advantages. As you're accelerating, vacuum is low and thus, the distributor does not advance the spark and helps to reduce detonation. When you're cruising down the highway, vacuum is high and the distributor advances the spark for better mileage. If you have to stomp on the gas pedal, vacuum goes low and the distributor retards the spark to keep from having detonation.

The arguement towards a vacuum advance distributor seems to be present but, in the performance world, (pre-computer driven engines) everyone ran a mechanical advance distributor because it gave you maximum advance (power) in a much more controlled fashion that a vacuum advance distributor.

just about everyone here runs a mechanical advance distributor and since the 60's I've done the same for every high performance engine I've built or owned and never had a bit of problems.

Just make sure that when you time your engine, you set the timing at 28 degree's advanced at 3,000 RPM's and you won't have any problems with detonation.

In my opinion, save your money for something that is more useful

Thanks Larry. Any more opinions out there?

Larry's opinion... in my opinion, is on the money !

As Dr. Clock saith: Larry is right on the money.

Besides, if you really wanted to run a vacuum advance you'd have to run a balance tube between your intake manifolds, which means getting new manifolds (or modifying your existing ones so they will accept the balance tube and don't leak after the mod). That's a moderate level PITA and I wouldn't bother.

gn

Here's a good article from Aircooled.net that explains most of the distributor choices:

Greg
http://www.aircooled.net/gnrlsite/resource/articles/distributor.htm

"Larry is right on the money"
You can pretty much always take that to the bank.

It seems like Larry's position on this is that its actually a good idea, but the payoff in terms of increased mileage and horsepower is not worth the cost. I just did the math and here is what I found. If I drive 5,000 miles a year @ $3.25/gallon and my mileage increases by 3 miles per gallon it will take me about 4 years to break even on the $240 cost of the VAD. However, the $240 cost includes tapping the carb to provide the vacuum, a new distributor with Comp-U-Fire electronic ignition (Comp-U-Fire is $64 from CB Performance). Here are a couple of other non-financial paybacks:

1. Never have to replace or adjust points (could do the same for $64)
2. Potential horsepower increase of 4 to 5%. (if it's true, would you even notice that?)

So, after typing this, I guess I feel like a 4 year payoff is just not worth it, (which is what I think Larry is really saying) but never having to adjust or replace points is worth $64 to me. I guess I'll be calling CB today.
PS. I'm not so sure that you would need a balance tube between the carbs. The vacuum should not leak and the tapped carb that is providing the vacuum should not be sucking more air than the non-tapped carb.
Troy

Several companies make a point eliminator (Compufire, Pertronix and Empi) I've used all 3 and each seems to work well. These devices are designed to fit into your standard 009 distributor requiring that you remove the points, condensor and the plastic wire bushing. Usually, it takes no more that 30 minutes to remove, replace and re-time your engine.

If you decide to go this route, make sure the floor of your distributor is clean as the modules receive their ground via the the distributor, additionally, place a drop of the "lite hold" loctite on the screw that holds the module to the distributor.

If the screw comes loose, it will cause an intermittent loss of ground causing a loss of spark.

I think Ricardo has installed a vac/ad dizzy with good results.

Troy:

You need the balance tube between manifolds because tapping the carb only on one side won't provide an adequate vacuum signal to the distributor diaphragm - you'll only be getting half of the expected vacuum draw (because you're only seeing vacuum from every other cylinder). If you watch it closely, especially at slower speeds, you'll probably see it pulsing, too. Not good for distributor performance.

The balance tube compensates for this, providing the proper amount (volume?) of vacuum that the distributor is expecting to see and at a more constant rate/level.

I think that there's an explanation of this on the Low Budget web site somewhere.

gn

As Bill says I installed the unit from Aircooled.net and am using it with dual Dells; the vacuum line is hooked to the left carb; the right one doesn't have the fitting, and the car works perfectly fine. If I remember correctly I didn't pay $240.00 for my unit.