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Thu Dec 12, 2019 7:20 pm

I have a 1968 beetle with a 113-905-205m distributor and a solex/bocar 30 pict 1 carburetor. The distributor is set at 0 degrees TDC statically and when the engine is running and the vacuum ports are disconnected from each other and plugged on the carburetor, it is still 0 degrees TDC. Idle is set at about 820.

When I connect the vacuum from the carburetor to the distributor, timing is advanced by the vacuum signal up to approximately 23 degrees BTDC and of course my idle increases.

Then I readjust the idle back down to the low 800 and when I rev the engine it maxes out at around 33 degrees BTDC.

Do I have a distributor and carburetor mismatch or am I doing something wrong here?
I really don't have a lot of experience with vacuum only distributors.
I didn't think it was supposed to provide a vacuum signal at idle.

I am supposed to adjust my timing with the vacuum disconnected and plugged, right?

Tried to balance things in place and take a video...

Thu Dec 12, 2019 7:43 pm

Are you checking the idle timing with the engine warmed up and the choke OFF / OPEN?

The vacuum advance port on the left side of the 30Pict-1 carb should be getting its vacuum from the venturi of the carb throat. When the choke is OFF this is a very weak vacuum that is created by the velocity of the air moving thru the narrow section of the carb throat. As engine rpms increase the air velocity increases and the vacuum increases.

If you check the vacuum signal from this port while the engine is cold and the choke is CLOSED you will find it is very high. The CLOSED choke creates a high vacuum in the throat below it. This is seen by the venturi port and the distributor timing is advanced. This is why you should only check the ignition timing AFTER the engine is warmed up and the choke is OFF.

Thu Dec 12, 2019 7:49 pm

This is after the engine has warmed up and the choke is off / open and the throttle arm is on the cam stop. I did this test today after I drove 45mins to get home from work.

The carb's vacuum nipple has its plug with tiny hole as well.

Thu Dec 12, 2019 7:57 pm

hylomatt wrote: This is after the engine has warmed up and the choke is off / open and the throttle arm is on the cam stop. I did this test today after I drove 45mins to get home from work.

The carb's vacuum nipple has its plug with tiny hole as well.

Make sure this is adjusted properly before setting timing. I like to have it backed off the stop to set timing, and then adjust it properly once the carb and distributor are set up. You want the throttle plate completely closed for those adjustments.

Thu Dec 12, 2019 8:02 pm

@beeltenut, good point, I'm going to warm it up and redo that now.

Thu Dec 12, 2019 8:32 pm

I can't turn the screw out far enough before the engine dies. So what's the set of steps here because maybe I have it all wrong.

1) start the engine, warm it up, choke off, etc
2) turn the idle adjusting screw out until the throttle plate is closed and the adjustment screw isn't touching the cam

At this step, the engine idle drops so low the generator light is flashing. i keep adjusting the idle mixture screw and timing to keep it going but this doesn't seem right to me. It's possible the throttle plate is worn and can't block the advance drilling properly.

After all of the above, the vacuum signal, once hooked up again, advanced the timing 19-20 deg.

Thu Dec 12, 2019 8:48 pm

@beeltenut, Backing the idle screw off the cam sounds like what you do for a 34-pict 3. Are you sure that's for a 30-pict 1 as well?

Thu Dec 12, 2019 9:12 pm

Here are the adjustment steps from vw-resource.com for a single-screw carb:
http://www.vw-resource.com/30PICT2.html
The procedures here are more like how you adjust performance carbs and unlike the how the later 2-screw 34Pict carbs are adjusted.

hylomatt wrote: The carb's vacuum nipple has its plug with tiny hole as well.
Huh?? Which plug are you talking about? All vacuum caps on unusued ports should be complete. A hole in the vacuum cap is a vacuum leak.

I just watched your video. You cannot leave any vacuum ports OPEN while making adjustments. If you are removing the vacuum advance hose from the carb you need to cap the open port before making adjustments. The open port represents a vacuum leak. The vacuum leak causes the idle rpms to drop so you end up having to open the throttle plate even more to raise the idle rpms to the normal level. This open throttle creates more vacuum at the vacuum advance port as the open throttle plate increases the air flow in the venturi.

Unplug the vacuum advance hose at the distributor end and plug the end of the hose with a screw or pencil. This seals the vacuum advance port of the carb. Make your carb adjustments to get the idle right at 850rpm. Now unplug the vacuum hose check if there is vacuum on the hose. Connect it to the distributor. With the throttle plate mostly closes you should have very little vacuum at the distributor so the timing should change very little, if at all.

One other thing to check is for a vacuum leak elsewhere.

Report back your findings.

Thu Dec 12, 2019 9:48 pm

@ashman40, I was stating that the vacuum port contained the inserted plug with a small hole in it, the vacuum-restricting insert. As opposed to a wide open tube with no restriction. It was a detail that volkzbitz asked me to verify.

In the video, there were no open vacuum ports. My hand was in there with my middle finger over the vacuum port, blocking it and then for a moment not blocking as I connected the vacuum hose.

Ok so I took the carb off and checked to see at which point the idle adjustment screw begins to open the plate enough to expose the vacuum port in the venturi. I'm probably exposing that port too much. I've checked for vacuum leaks around the intake/head connection area and found nothing but while I have the carb off and on the table, I realized that I can move the throttle shaft around a decent amount. That's going to be a leak, vacuum and probably gas too.

Fri Dec 13, 2019 5:04 am

Found these pics of vacuum port routing.

The above pic shows how the vacuum that reaches the distributor is low when the car is idling.

What you can see above is the two points in the carb throat where the vacuum comes from and that once the lower port is exposed it adds to the vacuum signal. The venturi vacuum is very small (~4inHg) while the lower port (once exposed) "sees" intake vacuum which is much stronger (~20inHg).

Try spraying carb cleaner into the left side vacuum port to confirm where the port gets its vacuum from? Carb cleaner should leak out from the inner port openings. Does the carb cleaner come out from both the upper venturi tube and one of the lower vacuum ports in the side of the throat? If your idle setting exposes the lower opening to intake vacuum at idle you may have found your problem.

That throttle shaft seems very loose. Your carb likely needs a full rebuild with new pressed in throttle shaft bushings.

Time to contact Tim at VolkzBitz. ;)

Fri Dec 13, 2019 9:54 am

@ashman, Thanks for the visuals. Yeah I've read through quite a few of the articles on here regarding the exposure of those lower drillings and the effects of doing so when unintended. The throttle shaft and/or bushings do seem very worn so it is time for VolkzBitz to do his thing.

Sat Dec 14, 2019 12:44 pm

For reference:
Here's a link to glutamodo's thread on the differences between the different model Solex carbs. VERY educational reading.
https://www.thesamba.com/vw/forum/viewtopic.php?t=185095

In the thread he identifies the vacuum advance ports inside the carb throat. Here is the pic from the Bocar 30Pict-1:

You can see the upper brass tube and the lower hole. Here is glutamodo's description:
glutamodo wrote: As mentioned, a while back, I posted some pictures as to how the internal "plumbing" of a 30PICT-1 (which used a vacuum-only distributor) compared to a 34PICT-3 (one that was originally matched with and SVDA) On the 30PICT-1, there is a medium sized port partially blocked by the throttle butterfly when closed, plus a second fitting higher up in the venturi that emerges from a brass pipe next to the main's discharge point. (This pipe was added on the 28PICT-1, the earlier 28PICT had a port up there, but it was just a hole in the side of the venturi. This leads me to believe that apparently a more appropriate vacuum signal is generated by having it be pulled from closer to center of the "depression" of vacuum.) The reason for this second port up there is maintain a smooth, steady and consistent amount of vacuum as RPMs are increased. Which is what is needed to feed a vacuum-only distributor.

If the lower port is only partially blocked it sounds like it us SUPPOSED to have some vacuum at idle. If so, as long as you set the idle timing with the vacuum hose disconnected and plugged you are good. If the port is even slightly exposed to the intake it WILL have vacuum at idle and will advance the distributor.

What I'd ask you to check is that the timing varies as you open the throttle and change the rpms. Once the throttle is open part of the vacuum comes from venturi port.
If the ignition timing is at max at idle and stays there regardless of the engine rpms... you have a problem.

As far as your throttle shaft being a vacuum leak... take the carb cleaner spray can and attach the red straw to focus the spray. Start the car warm up the engine. Place the open end of the straw at the gap between the carb body and the flange of the throttle shaft. This places the spray right where the air could leak into the end of the throttle shaft bore. In this pic, it would be to the right of the right red line.

Sat Dec 14, 2019 12:59 pm

@ashman40, If I set the timing and idle with the hose off and carb plugged, as soon as I reconnect the vacuum line, the timing advances from 0 TDC to ~19 BTDC. Then I rev it up and only get another 10 deg advance before the can is tapped out. That seems wrong and over-advanced at idle and under-advanced at full throttle.

Sat Dec 14, 2019 6:30 pm

hylomatt wrote: @ashman40, If I set the timing and idle with the hose off and carb plugged, as soon as I reconnect the vacuum line, the timing advances from 0 TDC to ~19 BTDC. Then I rev it up and only get another 10 deg advance before the can is tapped out. That seems wrong and over-advanced at idle and under-advanced at full throttle.

A 205M distributor only starts to advance when the throttle is cracked or opened on the carb and then the carb produces ported vacuum. At idle, your carb should not be putting out any ported vacuum.

If your 205M has the correct vacuum canister, it should vacuum advance 32°. If someone mounted an earlier vacuum canister from a 205K, it could advance only 24°. While the engine is under load running down the road, it will advance a bit more as well.

If you're getting any vacuum at idle to your distributor, you have carb issues for sure.

Sat Dec 14, 2019 6:43 pm

@wcfvw69, It's the correct canister because starting from 0 it'll advance all the way to 32 (maybe 33).

Yeah I think it might have been worn out. I've shipped it off to VolkzBitz to refurb.