Giving Up On Vacuum Advance Options

[Ansbacher]

Car = '74 2.0 Liter, Dual Dellorto Carbs

For years I have been 'adequately" running an 009 mechanical only distributor. Finally took the pervasive advice out there to go with a vacuum advance dizzy from a 1.8L 914. Since only one of my Dellorto carbs had an existing vacuum port (ported type), I had to drill a port in my other one (no problem there). I used good quality anti-pulse valves in the lines and measured a maximum vacuum of 12 inches of mercury with partial throttle.

Installed the 1.8 dizzy and set the timing, first without the vacuum lines attached. To satisfy my usual 30-32 degrees at 3500 RPM, the idle timing had to be at about 5-6 degrees (quite low for my setup which is happier at about 10 degrees. When I attached the vacuum lines my timing at 3500 RPM went sky high into the 40s. This seems way too high. Is this normal? Overall, I found the car to run better without the vacuum attached and the carbs plugged off.

Am I doing something wrong here? I don't like the numbers I am getting. Everyone said this was the way to go with carbs, but I am not seeing results. Advice appreciated.

Ansbacher

[nditiz1]

Ditch that distributor and get the correct one for vac adv. On that note the vac adv does not adv the timing at wot/3000+

The mechanical adv does that. Set to 10-12 idle 28-30 3000+.

Vac adv smooths out light throttle by over advancing to burn fuel more efficiently.

If you really want to scream install a 123distributor. Loved the one I ran on my 73 2.0 with carbs. It has vac adv too if you want to play around with it.

[pete000]

The 123 Dist is the way to go and no need for vac advance.

[Tbrown4x4]

I'll be watching this with interest. I'm going through a core 205 AA distributor right now. I wasn't planning on using the vacuum advance though. (1.7 with 40 IDA's)

If the total advance at 3500 rpm is really over 40, maybe you can install some kind of limiters to prevent the centrifugal from rotating the points plate that far. I agree about the vacuum advance not affecting total timing. I believe at 3500 rpm, the weights should be against their stops.

I also have an 009 in my car (installed by PO) that works OK, but was curious about other timing curves. I mean, can a distributor designed for a stationary engine really work well in a car?

Also, looking at a chart comparing 914 advance curves, I think the 1.8 just has a steeper curve that is shifted to a higher RPM range. Meaning it starts advancing later and is still advancing at a higher RPM.

Your timing numbers make sense because total advance = base timing + mechanical (at 3500 RPM).

I can put the stock 1.7 dizzy in, but the centrifugal can start as low as 700 RPM, and my idle speed is above that right now. I never worried about base timing because I just set the total at 3400 RPM and called it good. When I checked, the base timing was only 1 or 2 degrees. You should have smelled the exhaust!

Really eager to hear more opinions on this. A 123 Dist sound awesome, but certainly not in my budget.

[nditiz1]

I can't find the diagram right now, but someone posted the different distributors and curves. There are 2 or 3 I believe that can provide the curve you need which is a total mechanical advance of around 20 degrees (10 base + 20 full adv = 30 total timing at 3500)

Before using the 123 on my 2.0 I had the Mallory Unilite. It had swapable springs which you could change the spring rate and change the total adv.

While the 123 is costly at ~$450. You will never need another dist for your engine. The only other option is to source a used factory one or Mallory.

@Tbrown4x4 you are doing your setup an injustice by running that 009. If that 205 AA is listed as correct for your engine, get that cleaned up and working.

[BK911]

I've been running an 009 with carbs on a 1.7 for over 10 years now.
Car runs awesome.
If it ain't broke..........

[nditiz1]

I've been running an 009 with carbs on a 1.7 for over 10 years now.
Car runs awesome.
If it ain't broke..........

Just because you can run it doesn't mean you should (IMG:style_emoticons/default/beerchug.gif)

[tmessenger]

SVDA 034 here's what they say for timing: Use a stroboscopic timing light. Timing should be set initially at 30-32° BTDC at 3,500+ RPM, vacuum hose disconnected and plugged. Maximum advance, at 3,500+ RPM, vacuum hose connected, with no load on engine (car sitting still), light throttle, should not exceed 42-44° BTDC.

Tim

[cgnj]

How much vacuum @ idle? How much @ 3k?
7.5 degrees @ 800-900 rpm would be correct.

I think you are in the ballpark. High vacuum, low load you want to advance to increase mpg. The 10 degrees advance with the 009 is immaterial. It is compensation for the short curve.

[Ansbacher]

How much vacuum @ idle? How much @ 3k?
7.5 degrees @ 800-900 rpm would be correct.

I think you are in the ballpark. High vacuum, low load you want to advance to increase mpg. The 10 degrees advance with the 009 is immaterial. It is compensation for the short curve.

Since I am using ported vacuum, I have 0 vacuum at idle. It doesn't kick in until the butterfly starts to open (as it should). At 3K I have 12 inches HG. The car is much more responsive on pull out when the idle timing is above 8 or so degrees. With this distributor I can't keep it under my target 32 degrees at 3500 RPM when I set idle to anything above 5 degrees, and that is WITHOUT vacuum hooked up. Add the vacuum and it really goes off the chart, I lose power, and it starts to ping when I tromp on it. This is my dilemma.

Ansbacher

[914_teener]

I went through a tremendous amount of effort to find decent parts for distributors.

I just bit the bullet and got a 123.

Going on two years and flawless. With the blue tooth app. no mo problems.

[pete000]

I love my blue tooth programmable 123 so easy and dead accurate. Set it and it is spot on, so tunable. Car never ran so good in its life!

[porschetub]

My research indicated the anti pulse valve is only required if you only have one vacuum pickup,have you tried 2 vacuum lines from both carbs with a tee fitting to a single line on the distributor ?,the distributor will only advance to the range the vacuum unit was designed for so this seems strange you have this situation ,the advance place will only allow movement it its range also.
The so called SVDA used on 1600 beetles appears to work well on stock cam motors,and there is the Chinese repop which appears to be designed off the same unit,I have one of each and the repop one seems to be made well enough however don't think they will last as well as the originals (IMG:style_emoticons/default/confused24.gif) .

[Mark Henry]

Engine I just built for a customer, 914 2056cc with DTM for a bug.
Mallory unilight.

[Mark Henry]

I've had a couple guys ask about the linkage, nice bit of kit.

https://www.thesamba.com/vw/classifieds/det....php?id=2079800

[tmessenger]

Mechanical advance springs fatigue with age, with weak springs the full mechanical advance comes to quickly at a lower RPM. Have you checked the curve to see if the mechanical advance is correct?

Tim

How much vacuum @ idle? How much @ 3k?
7.5 degrees @ 800-900 rpm would be correct.

I think you are in the ballpark. High vacuum, low load you want to advance to increase mpg. The 10 degrees advance with the 009 is immaterial. It is compensation for the short curve.

Since I am using ported vacuum, I have 0 vacuum at idle. It doesn't kick in until the butterfly starts to open (as it should). At 3K I have 12 inches HG. The car is much more responsive on pull out when the idle timing is above 8 or so degrees. With this distributor I can't keep it under my target 32 degrees at 3500 RPM when I set idle to anything above 5 degrees, and that is WITHOUT vacuum hooked up. Add the vacuum and it really goes off the chart, I lose power, and it starts to ping when I tromp on it. This is my dilemma.

Ansbacher

[Ansbacher]

Answers to some questions posed of me:

Yes, I am using lines from BOTH carbs with a T-fitting to the vacuum pot. I have anti-pulse valves on BOTH lines in close proximity to the carbs. I tried a single valve but still got a pulse on the vacuum gauge. Using two, smoothed it out.

No, I have not checked the curve of the dizzy, and wouldn't know how to do it anyway. I am leaning toward the suggestion that I have worn out springs in the distributor. Is it hard to replace them?

Ansbacher

[r_towle]

Based upon what is going on, and your last question, I would suggest you take out the advance plates, clean and re grease them.
It’s simple.
It costs about a nickle.
Needs to be done every 40 years (IMG:style_emoticons/default/smile.gif)
http://www.914world.com/bbs2/index.php?sho...an++distributor

[72hardtop]

Don't attempt to 'T' the lines together. Pull off (1) port only pref. #4 closest to the distributor. Put the anti pulse valve as close to the carb as possible (arrow points to carb).

T'ing the lines will increase pulsing and lower the overall signal greatly.

be sure the distributor is clean and greased properly (advance plate). Use Super lube.

You should have no additional vacuum advance at idle once the hose is hooked to the distributor. Set timing to roughly 28-30 degrees fully advanced ~3200rpm's (hose off plugged). Ideally you should be getting 7-10 degrees additional vacuum advance hose attached.

Blipping the throttle with a vac gauge should show the needle flicking to 8-10in.

[IronHillRestorations]

One thing I forgot to mention is that the 1.8 distributor has an additional vacuum retard, and if you're connecting to the wrong vacuum port it will be a problem