TheSamba.com :: View topic - Distributor Seems to Retard on its own....SOLVED!

Mon May 19, 2025 9:50 am

I am having an interesting thing happening to my timing.
I have had the car running and driving now for maybe 500 miles. When it is running "warmed up, it seems to be running fine. I set the timing (statically) at 7.5 degrees BTDC, as per suggested.
Altho, I am noticing sluggish, terrible flat spots and off idle hesitations.
I am thinking timing, and sure enough, when I check it statically, I am always about 4 to almost 10 degrees retarded when I check it. Yesterday I re-set it at 7.5 degrees BTDC, and then drove maybe 30 miles, at highways speeds, and sure enough, when I went to recheck it statically, it had retarded to about 3 degrees BTDC. I did do a forum search, and saw something mentioned about some wearing of the lobes or something.

I have what (I think) is a stock SVDA, with a 34 PIC carb.

Mon May 19, 2025 10:30 am

Set the timing 28-30° btdc @ 3500rpm with the vacuum hose off.and the carb plugged.

Make sure you have it on the correct vacuum port on the carb.

Mon May 19, 2025 10:57 am

In my experience, static timing is good just to get it started. Follow Glenn's advice using a timing light, then test again - drive, etc.

Mon May 19, 2025 11:09 am

Remove the distributor cap and grab the rotor with your hand. Rotate it CW. It should feel like you are compressing a spring. Release the rotor and it should spring back to it's original position. This is the mechanical advance working.
If the spring back seems sluggish or gritty the mechanical advance mechanism may be in need of lubrication. To do this, remove the rotor and look down the top of the shaft. There should be a felt pad. Drip some engine oil onto the pad. If the pad looks very dry, add extra. Oil drips from this pad down into the distributor to lube the internal mechanism. You could even rotate the rotor back and forth to work the oil in.
Going forward, add a few drops of oil each time you change the oil... You know, that little bit of oil that still remains in the container at the end of the oil change? Now you have a use for it!

When you have a min, post the model number stamped into the body of your distributor. Better yet, post a pic!

Mon May 19, 2025 11:11 am

I had a similar experience to yours. Are you sure the distributor clamp is tight? Try turning the distributor AFTER you've tightened the clamp, it should not move. I needed to replace my clamp because it would not tighten up enough and would slip over time under load.

Mon May 19, 2025 11:30 am

Number one, you need to get and use a timing light when setting your timing. The static timing method isn't very accurate, and is generally used to just get the timing into the initial "rough ballpark" -- i.e. where the engine will idle long enough so that a timing light can then be used to set the timing correctly.

Number two, if you don't have an engine analyzing meter with measurement functions for engine RPM and dwell, you'll want to get and use one of those as well when you're doing your tuning. Points need to be set first to the correct dwell range, and then the timing can be adjusted after that (i.e. since dwell affects timing, but timing doesn't affect dwell).

The lobes on the distributor shaft can wear over time, but not anywhere near fast enough to account for the behavior you're describing. If you're using really cheap/crappy points, the little rubbing block on those might be wearing down quickly - ? Otherwise, I'd suspect your distributor clamp may be set a bit loose (or is perhaps loosening up when engine running - ?), as noted by a8ked above.

Mon May 19, 2025 2:02 pm

baldessariclan wrote: Otherwise, I'd suspect your distributor clamp may be set a bit loose (or is perhaps loosening up when engine running - ?)
Once you have your timing set, use a sharpie to make a single line from the distributor body down onto the dstributor clamp. If the distributor is vibrating and rotating you will be able to tell because the line will be split.

Mon May 19, 2025 6:19 pm

ashman40 wrote: Remove the distributor cap and grab the rotor with your hand. Rotate it CW. It should feel like you are compressing a spring. Release the rotor and it should spring back to it's original position. This is the mechanical advance working.
If the spring back seems sluggish or gritty the mechanical advance mechanism may be in need of lubrication. To do this, remove the rotor and look down the top of the shaft. There should be a felt pad. Drip some engine oil onto the pad. If the pad looks very dry, add extra. Oil drips from this pad down into the distributor to lube the internal mechanism. You could even rotate the rotor back and forth to work the oil in.
Going forward, add a few drops of oil each time you change the oil... You know, that little bit of oil that still remains in the container at the end of the oil change? Now you have a use for it!
When you have a min, post the model number stamped into the body of your distributor. Better yet, post a pic!

OK thanks. Here's a picture.
It's a mirror image but it's the best I could do..

Bosch # "0 231 170 034" (can just see the "034" part) then vw part number "043 905 205" (you can see this one pretty good)

Ya gotta trust me on this one.. Mirror image, went BATTY trying to read it then make sure I had it right. VW part number shows here, and you can see the last 3 digits of the Bosch distr. number (034)

Mexican made SVDA?? hmm..

What I did was
a) make sure the dizzy was clamped TIGHT: it was....check
b) rotate rotor CW and see if it slid back; well, it only went about 2-3 mm, but it went right back when released. Check. (BTW, the diaphragm moves when I suck the tube (yuk!)
c) Put drops of oil on the felt portion of the main shaft. Check

I have a timing light ordered, and will try and get that done ASAP.
Stand by!

Tue May 20, 2025 8:21 am

Did you lube the cam lobes for the points with grease?

Tue May 20, 2025 8:22 am

halfassleatherworks wrote: Did you lube the cam lobes for the points with grease?
Done! Thanks
CC

Tue May 20, 2025 11:26 am

When you suck on the tube, :lol: Do you block off the end with your tongue and wait 10 seconds?

Tue May 20, 2025 11:39 am

Grab the distributor and try to turn it with your hand. If you can turn it the bolt isn't tight enough.

Disconnect the hose from the carburetor and plug the hole. Set the timing at 7.5 degrees to the right side of the engine at or below 900 RPM. Then reconnect the hose to the carburetor. Go drive it around. Nothing should move when you check the timing again.

If you having a flat spot and you did the timing above correctly most likely your vacuum canister is blown.

Change the condenser out just to rule that out. It can cause issues sometimes.

Check your rotor and inside the cap.

Wed May 21, 2025 7:01 am

bsairhead wrote: When you suck on the tube, :lol: Do you block off the end with your tongue and wait 10 seconds?
I'll try it. I assume a good outcome would mean the plate stays in place when vacuum is on, and releases after its off......

Wed May 21, 2025 7:03 am

heimlich wrote: Grab the distributor and try to turn it with your hand. If you can turn it the bolt isn't tight enough.
Done and did it. She's not able to move when twisted.

heimlich wrote: Disconnect the hose from the carburetor and plug the hole. Set the timing at 7.5 degrees to the right side of the engine at or below 900 RPM. Then reconnect the hose to the carburetor. Go drive it around. Nothing should move when you check the timing again.

If you having a flat spot and you did the timing above correctly most likely your vacuum canister is blown.

Change the condenser out just to rule that out. It can cause issues sometimes.

Check your rotor and inside the cap.
That will have to wait until I get the timing light. It's coming!

Wed May 21, 2025 7:02 pm

If you have a Mexican Bosch 034, you're fine. They are excellent distributors since Bosch made them in Mexico with their tooling. I've restored 100's of them and they have the same internal parts as the German made versions. The specs are the same as well.

You need a Mighty vac hand vacuum pump to check the vacuum canister. The tongue test doesn't work.

Under the rotor is a felt that should have a few drops of oil added every 3k miles. It lubricates the upper points cam on the mainshaft. If you twisted the rotor and didn't feel it pivot against the advance springs then it's possible it's stuck. I see this a lot of distributors I restore. The previous owners never lubricated that wick.

Wed May 21, 2025 8:42 pm

What is your idle speed at?

What carb port are you vacuumed into?

Thu May 22, 2025 2:19 pm

VW_Jimbo wrote: What is your idle speed at?
What carb port are you vacuumed into?

Idle speed 900 RPM
Vacuum port Drivers side side of carb

Sat May 24, 2025 7:15 pm

I got my timing light Thursday. It didn't work! I sent it back, new one came today so.....

1) First I checked vacuum. At idle, side port 0 mmHg. AT 1500+rpm, snapped up nicely to 20 mmHg. Looks good there, right?
2) Put a witness mark on the dizzy. Nothings moving...
3) I took it upon myself to remove and clean (as best as I could) the dizzy, and lube the moving plate and lobes.
4) Checked motion of plate with Mighty Vac pump (thx HF) It seemed to be moving fully (I think) with 15 mmHg vacuum, and the vacuum looked like it was holding, maybe s-l-o-w-l-y falling....(boring video-BTW, whey is the darn thing so low quality??)

5) Set the timing at 7.5° BTDC statically. Took off vacuum hose from side of carb.
6) Confirmed setting with light-7.5° BTDC. Good...
7) Replaced vacuum. Ide setting still at 7.5° BTDC. Then ran it up to 3000 RPM. Got maybe 15° of advance. Did it about 5 times.... waiting a few a seconds between. Averaged about 15 ° BTDC . couple of times maybe 25 ° BTDC, but it wasn't consistent. Drove around for maybe 20 miles; 55 mph highest, but mostly in-town speeds. Rechecked the timing statically.
8) Yup, it had moved, this time advancing to maybe 10° BTDC.
Do I need a new distributor?? Suggestions? I'd like to keep the SVDA format-don't wanna go to a .009 or a DVDA

Sat May 24, 2025 7:22 pm

Vacuum looks good. It's not leaking down fast enough to call that a leak. You should be getting about 8 to 12 degrees of advance from the vacuum canister. That little movement will make a lot of advance.

From the mechanical portion of the distributor you should be getting 20 to 25 degrees advance from the distributor.

If you set the timing to 7.5 degrees at idle (less than 900 RPM) how does everything work?

No need to buy a new distributor. That one can be rebuilt very easily if it needs it. All the parts for it are available.

Sun May 25, 2025 5:59 am

Chinaclipper wrote: 7) Replaced vacuum. Ide setting still at 7.5° BTDC. Then ran it up to 3000 RPM. Got maybe 15° of advance. Did it about 5 times.... waiting a few a seconds between. Averaged about 15 ° BTDC . couple of times maybe 25 ° BTDC, but it wasn't consistent. Drove around for maybe 20 miles; 55 mph highest, but mostly in-town speeds. Rechecked the timing statically.
8) Yup, it had moved, this time advancing to maybe 10° BTDC.
Both the checking procedure and results you are describing in these last couple steps sound a bit bizarre and inexplicable to me — ??
Trying to break it all down a bit further:

1) Yes, do to the nature of the ported vacuum signal, you should see no change in the 7.5° BTDC timing reading at idle, regardless of if the vacuum advance line is connected or not.

2) However, once you increase the throttle / engine speed beyond idle, you should get a large jump of vacuum advance. For this reason, you need to always check the centrifugal/mechanical advance w/ the vacuum advance line disconnected — very important!

3) With the vacuum advance disconnected and engine speed at 3,800+ rpm, you should be seeing a total advance of 28° - 32° BTDC (i.e. 7.5° idle timing setting + ~22° - 23° mechanical advance).

4) If you mistakenly do the total centrifugal/mechanical advance check incorrectly with the vacuum advance still connected, you should see total advance readings which are even higher than the 28° - 32° BTDC limit, due to the additional vacuum advance present.

5) However, you seem to be describing seeing a widely varying total advance reading of only 15° to 25° BTDC at 3,000 rpm (?) with the vacuum advance line still connected — ??

6) Once again, a static timing reading of 10° BTDC means very little to me, since it is an inherently inaccurate/imprecise method of checking and setting timing. Use the timing light to get an accurate reading of if your timing has changed, and what it now rests at.

Based on the above information and descriptions, the timing behavior you described seems very erratic, and makes no sense to me. However, at this point am still unsure whether it’s due to a faulty distributor, or operator error (or possibly both - ?).

Not trying to be overly critical here, just trying to help. The details in these check and adjustment procedures are very important to understand and follow correctly — otherwise you’ll get no clear idea of what’s going on, and can end up “chasing your tail”…