Giving Up On Vacuum Advance Options

[Ansbacher]

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.

With this distributor, there is no way I can set timing to 28-30 degrees. If I do, it puts my idle timing at 0 degrees or less, making it impossible to run good at idle. Also, I found that T-ing the lines from both carbs smoothed the vacuum out.

Ansbacher

[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.

With this distributor, there is no way I can set timing to 28-30 degrees. If I do, it puts my idle timing at 0 degrees or less, making it impossible to run good at idle. Also, I found that T-ing the lines from both carbs smoothed the vacuum out.

Ansbacher

You need to limit the advance (tweak the stops) the Type-4 loves some initial advance roughly 10-12 initial. You only need 1 vac line.

The additional advance (vac advance) will be load sensed. Load being throttle position. Get a bung welded in and start tuning with an LM-2.

Part throttle....16-17 AFR

WOT....12.5 - 13.2 or so

[Red72]

Jumping in here, and I'm sorry to hijack it somewhat, but this seems to at least be an active dizzy thread.

I'm fairly new to distributors, and I'm looking to tweak the curve with the springs and stops on my pertronix unit on my 1.7l engine. I'm looking to combine two different spring weights in order to control the initial (off idle), and total advance. The question I have is, will I still get full advance if I limit the advance on a LIGHT spring to something like 6 degrees above initial, and then allow the HEAVY spring to go all the way to 20 degrees advance, resulting in something like 28 full advance?

Thinking that this will bring advance on early, but then climb more slowly up to 3500rpm. This seems to more closely match the curves of non-vacuum, non-009 units.

I realize the answer here seems to be 'get the 123 unit', but the dollars for that isn't in the cards right now.

Thanks.

[tmessenger]

I went through this with a Triumph TR3 a couple of years ago, the factory distributor springs were NA and the old springs were shot. I modified other springs to work and it was just a process of trial and error to get the curve right. I used an electronic inductive tachometer to dial in different engine speeds and then checked the advance at the crank with a timing light. It took a while but I tweaked the springs until the mechanical advance curve was correct.

The only other option I know of is to find someone that has an old sun distributor machine to set up the mechanical advance.

Tim

Jumping in here, and I'm sorry to hijack it somewhat, but this seems to at least be an active dizzy thread.

I'm fairly new to distributors, and I'm looking to tweak the curve with the springs and stops on my pertronix unit on my 1.7l engine. I'm looking to combine two different spring weights in order to control the initial (off idle), and total advance. The question I have is, will I still get full advance if I limit the advance on a LIGHT spring to something like 6 degrees above initial, and then allow the HEAVY spring to go all the way to 20 degrees advance, resulting in something like 28 full advance?

Thinking that this will bring advance on early, but then climb more slowly up to 3500rpm. This seems to more closely match the curves of non-vacuum, non-009 units.

I realize the answer here seems to be 'get the 123 unit', but the dollars for that isn't in the cards right now.

Thanks.

[Rand]

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..........

I love that yours runs awesome. But can you imagine a tuning that would bring another 20hp with the same mileage? I bet Joe Sharp could.

Back on topic, should he use vacuum advance or retard? I found it to be differential because of difference years, dizzyy's, etc.

I had one experience where the retard wasn't working and it made my idle high. Fixed with a part replacement. Carbs will be always suck when you get out of your optimum altitude. FI adjusts as needed. Is there really a need to keep debating it?

.

[72hardtop]

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..........

I love that yours runs awesome. But can you imagine a tuning that would bring another 20hp with the same mileage? I bet Joe Sharp could.

Back on topic, should he use vacuum advance or retard? I found it to be differential because of difference years, dizzyy's, etc.

I had one experience where the retard wasn't working and it made my idle high. Fixed with a part replacement. Carbs will be always suck when you get out of your optimum altitude. FI adjusts as needed. Is there really a need to keep debating it?

.

Not a debate with an EFI system. But unless one is traveling between altitudes on a regular basis (most aren't). I prefer a dual set up. More horsepower. If one is going EFI go with a modern set up not the stock one.

[Rand]

Did you just suggest that you can create so much horsepower in a slim sliver of a band (whichI will argue) that you are actually suggesting carbs are better? Ignoring altitudes (which is only one of the many huge side benefits of FI and why NO car comes carbs anymore)

The stock one. Still better than carbs? Which were implemented and when? Stone wheels also have the best traction.

[Rand]

Let me take this second to say that I respect Joe Sharp. And he sure as hell knows how to tune carbs.

Anything I said above that sounded like I hated carbs should be re-looked at from where I was coming from.

JoeS actually offered get me a six running years ago. Thank you.

The point of my post is not to stir anything up more than thought.

I don't hate carb. It's just freaking obvious that FI is more efficient than carbs proven for decades. I LOVE the sound of carbs. I got no dog in the fight. It's just conversation. When those carb throttle bodies open full, we all go silent to listen. (IMG:style_emoticons/default/wub.gif)

[MarkV]

No doubt fuel injection is better. Many of us have carburetors and prefer them even though injection is superior. The stock injection doesn't allow for much in the way of engine modification.

I think the OP's question was about dual carbs and vacuum advance.

If you can find an old Mallory distributor they have an advance mechanism that is easily adjusted without having to use a distributor machine.

[72hardtop]

Did you just suggest that you can create so much horsepower in a slim sliver of a band (whichI will argue) that you are actually suggesting carbs are better? Ignoring altitudes (which is only one of the many huge side benefits of FI and why NO car comes carbs anymore)

The stock one. Still better than carbs? Which were implemented and when? Stone wheels also have the best traction.

The stock EFI systems have many parts that are NLA. Which is why if you go EFI go modern. As for a dual set up....if properly jetted you'll create more horsepower then an EFI set up.

Ive tuned my Weber 40's in my 2056 T-4 hardtop bus and get better MPG's than the stock Type 4 powered buses with stock fuel injection.

Cold start drive-ability is probably the best thing about an EFI set up.

[914_teener]

Ok....I'm an EFI guy so for carbs it's the way back machine for me.

So, stupid question (mine) with your first post and subsequent ones in mind...forget about EFI better or not.

Stupid question:

When you say you are using "ported" vacuum, where in relationship to the throttle plate is that that port, look at a side view of the carb?

[914_teener]

https://web.archive.org/web/20001007043902/...ch/distrib.html


Thread on the Bird Board a while back that Dave Darling wrote.

Went through this myself when I was trying to match a stock dizzy to an EFI system. I finally got tired...from a time perspective and went with the 123.


It is important as to where the port vaccum is in relationship to the throttle plate.

So manifold port? Carb port? Below the Throttle plate or above it?

Take a picture and post it.

[72hardtop]

Ok....I'm an EFI guy so for carbs it's the way back machine for me.

So, stupid question (mine) with your first post and subsequent ones in mind...forget about EFI better or not.

Stupid question:

When you say you are using "ported" vacuum, where in relationship to the throttle plate is that that port, look at a side view of the carb?

Above the throttle plate. You should have zero vacuum with the throttle closed.

[914_teener]

Well then another dumb bunch of questions:

Isn't the vacuum below the throttle plate manifold vacuum and not "ported" vacuum?

At part load or idle you want it above the plate not below IIRC.

So static timing set...then as the TP opens vacuum increases to the point where they equalize and the mechanical takes over. Isn't this is how it is supposed to work?

I dont' remember.


Next dumb question:

Is the diaphragm tested as working?

Next:

Is the AFM right? Too lean....slow....too rich fast.

[72hardtop]

Corrected. Got ahead of myself there. Ported vac always with a distributor vac advance.

Distributor on mine is fairly new (Bosch SVDA). Used an LM-2 for jetting.

[tmessenger]

Ported vacuum with vac port covered by the throttle plate at idle, connect in your vacuum gauge and check that you have no vac at idle.

Jake Raby likes to set up carbs at a/f 13:1 throughout so a bit different than the lean burn under light loads that John at aircooled.net aspires to.

Note: this is a heavy read.
The mother of all carb tuning threads (including timing theory) is on the samba here:

https://www.thesamba.com/vw/forum/viewtopic...c74c2cf44f55a21

Good luck,

Tim

Corrected. Got ahead of myself there. Ported vac always with a distributor vac advance.

Distributor on mine is fairly new (Bosch SVDA). Used an LM-2 for jetting.

[cgnj]

Ported vacuum with vac port covered by the throttle plate at idle, connect in your vacuum gauge and check that you have no vac at idle.

Jake Raby likes to set up carbs at a/f 13:1 throughout so a bit different than the lean burn under light loads that John at aircooled.net aspires to.

Note: this is a heavy read.
The mother of all carb tuning threads (including timing theory) is on the samba here:

https://www.thesamba.com/vw/forum/viewtopic...c74c2cf44f55a21

Good luck,

Tim

Corrected. Got ahead of myself there. Ported vac always with a distributor vac advance.

Distributor on mine is fairly new (Bosch SVDA). Used an LM-2 for jetting.

]Good link Tim, going to take a week to read it all (99 pages). I find myself drawn to the "we tune carbs/timing with the wrong approach".

[tmessenger]

There are 11 years of knowledge in those 99 pages. I started with it about a week ago and I'm now on page 85. If your engine is mechanically healthy to start with you'll be way ahead of the curve when it comes time to solve carb tune and timing issues with this knowledge.

Do yourself a favor and copy and past the basic concepts into a word doc as you go and anything else that is relevant to you. I went through the first 20 pages and then the light went off and ding I had to backtracked to collect the gold into a condensed version for future reference.

You're also going to need one of these or something like it if you don't already have one:

https://www.14point7.com/products/sigma-lam...ntroller-free-2

Tim




[quote name='72hardtop' post='2685043' date='Jan 30 2019, 10:46 PM']
Corrected. Got ahead of myself there. Ported vac always with a distributor vac advance.

Distributor on mine is fairly new (Bosch SVDA). Used an LM-2 for jetting.
[/quote]
[/quote]
]Good link Tim, going to take a week to read it all (99 pages). I find myself drawn to the "we tune carbs/timing with the wrong approach".
[/quote]

[72hardtop]

You can garner a lot from that thread with the first 20 pages alone.

Remember....

Get above 14:0 - 15:5 on the progression circuit and below it (14:0 - 15:5) when on the main jets. Ideally when under load/WOT... 12:5-13:2 or so. 14:0 -15:5 is the highest area for EGT's.

Load = Throttle position

No lean tune cruising with mechanical only distributors.

[tmessenger]

72hardtop

Sounds like we have very similar engine builds, mine is:

Fat Performance built 2056 long block, 42x38 ported and polished heads, Fat 442 cam, 8.3 : 1 compression 4k miles on the build.

I just bought this car 6 weeks ago so am just now starting with the carb tune. The current configuration I inherited :

40 IDF Webers, 32mm venturi's, 60 idle jets, 135 mains, F11 emulsion tubes, 175 air's, SVDA distributor with stock 2.0 heat exchanges and Triad muffler.

I've just ordered an A/F gauge to start the process.

Can you tell me how your finalized carbs jetting came out and your A/F readings? Could be useful to both of us to compare notes.

Thanks, Tim

You can garner a lot from that thread with the first 20 pages alone.

Remember....

Get above 14:0 - 15:5 on the progression circuit and below it (14:0 - 15:5) when on the main jets. Ideally when under load/WOT... 12:5-13:2 or so. 14:0 -15:5 is the highest area for EGT's.

Load = Throttle position

No lean tune cruising with mechanical only distributors.