TheSamba.com :: View topic - 1970 beetle. Vaccum advance distributer or no vaccum advance?

Sat Apr 03, 2021 10:47 pm

I have a 1970 standard beetle. When I bought the car it had a single vaccum advance distributor installed and I never questioned it. Over the past three years I have replaced the carb the plugs, wires, coil and distributer. It was running fine for a while then all of sudden after it was warmed up it would struggle and even backfire. It ideIed fine when it was cold but after about a mile of driving it would all go to crap. I timed it and re timed it and even put another new carb as all of my other idle / running issues seemed to be carb related and still the same, idle fine cold then after it warmed up it went to crap. I noticed the fuel filter was empty so I also changed the fuel pump and I also pulled the gas tank (its new too) and blew out the metal fuel line with an air compressor at 40 psi and still it ran crappily after it got warm. So I was going to replace my new distributor with another new one when I looked up my beetle on JBugs it came back with both a vaccum advance distributer and a non vaccum advance. So I removed
The hose from the distributor to the car and put rubber plugs on both the distributor and the carb and now it runs but it feels a little held back at freeway speeds. So my question is what kind of distributor should the carb have and is plugging the carb and the distributor vac ports the same as running a non vaccum distributor. On my engine (1600) I currently have installed

Pertronix flamethrower svda distributor
Pertronix 50000 coil
Ngk iridium plugs
Ngk wires
Brosol fuel pump
K&N air filter
30/31 pict 3 carburetor

All parts listed have less than 1500 miles on them. So could the vac advance on my newish drisituber have gone bad and do I even need to have a vac advance distributer in the first place? I really appreciate your help.

Thanks

Brian

Sun Apr 04, 2021 1:27 am

I think that an original well tuned distributor is the best choice. The carburetor and the distributor works in Tandem to achieve the best performance. A good solution can be a 123 distributor with the vacuum port, so you can upload via usb the prober curve ( vacum and machanical) for your carburator.

Sun Apr 04, 2021 3:47 am

Don't forget to adjust your valves.

I'm a big fan of the 68-70 single port engines. I use a 113-905-205M distributor on my single port, with a Brosol H 30/31. That combo has always worked very good for me.

I'm hoping for a new 30PICT-3 soon from https://www.volkzbitz.com

That's the carb originally on your 70. Pair that with a 113-905-205T, that is probably what you already removed, and I bet you'd be happy. Glenn (here on the forum) can sell you one or restore your original dizzy. That's how to make your single port get up and go.

Sun Apr 04, 2021 3:48 am

You have a H30/31PICT carb so your best option is a 205T single vacuum distributor which was the one that originally came on the engine

Sun Apr 04, 2021 2:02 pm

Can you specifically identify the model of your old carb and old distributor combo? Not all carb+distributor combos work well.

You mention your current combo is a 30/31 carb (aka. H30/31) and a Pertronix SVDA distributor. The normal vacuum advance port on the left side of the 30/31 carb does not provide enough vacuum to work with the SVDA vacuum canister. Luckily, most 30/31 carbs have multiple vacuum ports. One of them will likely work with your SVDA.

Picture borrowed from glutamodo showing H30/31 vacuum ports:

In the above pic, the left side port on the carb is "venturi vacuum". This is too weak for the SVDA distributor's vacuum canister. Plug this port and any other ports on the carb you are not using. Instead, connect the SVDA vacuum canister to the bottom right rear-facing vacuum port in the above pic. The only port that is angled up. This is normally connected to "ported vacuum" which is what the SVDA was designed to work with.
If you have a vacuum gauge, ported vacuum will have zero vacuum when the throttle plate is fully closed. But as soon as the throttle is cracked open, ported vacuum is exposed to full intake vacuum. This means just off idle the vacuum is very strong and results in the SVDA distributor spiking the timing advance. Also, when the car is cruising at constant speed and the throttle plate is mostly closed on a high rpm engine, the vacuum will be high resulting in max vacuum advance. This results in better fuel economy and power. At high vacuum you should get a reading around 15~20in-Hg. This will fully advance the vacuum advance on an SVDA distributor. If you place your vacuum gauge on the left side port of the 30/31 carb you will likely only see a max of around 5in-Hg at high rpms, barely enough to even get the SVDA to advance at all.

Sun Apr 04, 2021 2:47 pm

Borrowed from myself, :wink: here is when I did my round of testing on an H30/31PICT with a German 034 SVDA.

I used a plastic hose because I wanted to get the hose up and out of the way of the throttle arm.

Sun Apr 04, 2021 10:52 pm

Dang,

I was hoping somebody would say that it doesn't need a vacuum advance distributer. I drove it today from Ocean Beach to Miramar today (15 Miles Each Way) on the freeway ay 70 -75 mph (felt like 120 :) On the surface streets I drove it like a pissed off teenager and it drove Great!. Just Fantastic. Tomorrow I'm going to take even farther, 25 miles each way. The one thing that I have learned so far in my all of my dubbin' is that if it works go with it!

I really appreciate all of the replies. Even though it only has 37k original miles and I'm the 2nd official owner the original owner let her grandson have it when he was in high school in the early 90's and he put on cheap parts (distributor and carb) as well as some other questionable "improvements" The parts I took of were not original VW or Bosch. I have been very careful to buy the absolute best I can when I have been working on it. It is the most original, complete beetle I have even touched. It sat underground in a parking garage for over 25 years before I happened on it. and I bought it off of the original owner. She bought it new for herself as a retirement gift and she was selling it as she was going into an assisted living facility. I named the beetle Donna in her honor. I did buy a $200 brosol carb new from wolfsburg west but it ran like crap out of the box. I took it to a mechanic to tune who said they tuned carbs they charged me over $300 and it ran even crappier. than I saw a carb on amazon for $60 from maxspeedrods with great reviews and it worked great out of the box. The way I see it I could buy 6 of those for the price of having a mechanic breathe on it so why not if anybody lives in san Diego Ill happily sell you my brosol with literally only dozens of miles on it for $100. PM me

I really want to meet up with other VW people in san diego. I'm going to the coffee and cars VW san diego meet up on June 27th in Mira Mesa. maybe Ill see you there. Ultimately I want a 65 cabriolet convertible in Bahama blue (that what my dad had and what I grew up in ) or a convertible ghia. I'm afraid of letting go of this beetle because when is the next time I'll find a 51 year old one owner car with 34k miles (just under37 now) anyway I just want to enjoy my mid life crisis without the speeding tickets

I love the Samaba! Thank You Everybody even if you didn't tell me what I wanted to hear.

Sun Apr 04, 2021 11:43 pm

Your symptoms sounds like a stuck choke.. the Bentley manual even has a topic about freeing up a stuck choke shaft. It's not uncommon. You mentioned all the other stuff you've done, have you adjusted the choke on any of the carburetors you've had on there? Check the shaft for smooth movement.. it will be obvious if it's too stiff.
As for carbs running like crap, sometimes they do and it's hard to figure out where to start. The Bentley manuals are pretty good at troubleshooting specific parts or circuits on the carbs, and you can generally interpolate to other aftermarket types. One of the best things for a carb is a good ultrasonic tank cleaning.. The passages are pretty small and it doesn't take much more than a flake of rust to keep the entire idle circuit from working. Also blow all three of the jets out with compressed air after soaking them.

I hate to hear you piddled good money away for a mechanic to not fix the carb issue. Stuff like that is what drives me to do all of my own repairs and work, even picking up new skillsets like machine shop work, just to be able to correctly diagnose and fix stuff.

Fri Apr 09, 2021 3:22 am

Aldous92107 wrote: Dang,

I was hoping somebody would say that it doesn't need a vacuum advance distributer. I drove it today from Ocean Beach to Miramar today (15 Miles Each Way) on the freeway ay 70 -75 mph (felt like 120 :) On the surface streets I drove it like a pissed off teenager and it drove Great!. Just Fantastic. Tomorrow I'm going to take even farther, 25 miles each way. The one thing that I have learned so far in my all of my dubbin' is that if it works go with it!

I really appreciate all of the replies. Even though it only has 37k original miles and I'm the 2nd official owner the original owner let her grandson have it when he was in high school in the early 90's and he put on cheap parts (distributor and carb) as well as some other questionable "improvements" The parts I took of were not original VW or Bosch. I have been very careful to buy the absolute best I can when I have been working on it. It is the most original, complete beetle I have even touched. It sat underground in a parking garage for over 25 years before I happened on it. and I bought it off of the original owner. She bought it new for herself as a retirement gift and she was selling it as she was going into an assisted living facility. I named the beetle Donna in her honor. I did buy a $200 brosol carb new from wolfsburg west but it ran like crap out of the box. I took it to a mechanic to tune who said they tuned carbs they charged me over $300 and it ran even crappier. than I saw a carb on amazon for $60 from maxspeedrods with great reviews and it worked great out of the box. The way I see it I could buy 6 of those for the price of having a mechanic breathe on it so why not if anybody lives in san Diego Ill happily sell you my brosol with literally only dozens of miles on it for $100. PM me

I really want to meet up with other VW people in san diego. I'm going to the coffee and cars VW san diego meet up on June 27th in Mira Mesa. maybe Ill see you there. Ultimately I want a 65 cabriolet convertible in Bahama blue (that what my dad had and what I grew up in ) or a convertible ghia. I'm afraid of letting go of this beetle because when is the next time I'll find a 51 year old one owner car with 34k miles (just under37 now) anyway I just want to enjoy my mid life crisis without the speeding tickets

I love the Samaba! Thank You Everybody even if you didn't tell me what I wanted to hear. As far as I'm concerned pretty much ANY street engine needs a vacuum advance distributor. There's a reason why its there. If you want to see how important it is, take a ride in a proper running car and then cap the advance line...its like loosing a cylinder at low rpm

Fri Apr 09, 2021 3:30 am

Also another thought. Have you rechecked the fuel supply? Why was it starving for fuel in the first place? If it was crap in the tank...it is likely back already and needs to be at least removed and flushed. Also are all your cooling tins and seals in place? Retarded timing at highway speed can cook your engine. I would hook the advance back up ASAP.

Fri Apr 09, 2021 6:21 am

I read above that the OP had a good time taking his Beetle out for a long drive. It is not clear to me if the problem is fixed, or not? :?

Fri Apr 09, 2021 7:11 am

I use vintage German 009 distributors (mechanical advance only) on both my 1835cc engine with single Weber and my 1600cc engine with 30/31 PICT on an adapter for DP manifold, very satisfied.

Note that Brazilian, and more so Chinese 009 copies are not considered as good of quality.