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bsairhead
Samba Member
Joined: October 08, 2008
Posts: 4486
Location: viroqua wi.
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 Posted: Sun May 25, 2025 8:58 am Post subject: Re: Distributor Seems to Retard on its own.... |
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| 1 disconnect the vacuum line. 2 plug said line. 3 rev engine till no more advance shows with light. 4 at that rpm set timing at 30 degrees. 5 unplug and replace line, done. |
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VW_Jimbo 
Samba Member
Joined: May 22, 2016
Posts: 11155
Location: Huntington Beach, CA
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| Posted: Sun May 25, 2025 9:07 am Post subject: Re: New Information... Now what?? |
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| baldessariclan wrote: |
| 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.
 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”… |
Excellent! Very succinct. Follow this!
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Chinaclipper
Samba Member
Joined: October 03, 2019
Posts: 810
Location: Somewhere in the great Midwest
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| Posted: Tue May 27, 2025 6:09 pm Post subject: Re: Distributor Seems to Retard on its own.... |
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OK yesterday I did exactly as suggested.
I set idle to 800 rpm (wow)
I plugged vacuum on side of carb, and set timing with the light to 7.5° BTDC
I ran it up to 3000+ RPM and saw with the light a nice 30° advance! I tried to film it but it just didn't seem to like it. the camera wouldn't show it.. hmmm.
Checked it at idle (800rpm) again and it was right there at 7.5° BTDC.
So all good.
I will try it out tomorrow; and re-check after  .
Today and yesterday there was just too much other distractions, and it was raining.. yuck...
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bsairhead
Samba Member
Joined: October 08, 2008
Posts: 4486
Location: viroqua wi.
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| Posted: Tue May 27, 2025 6:38 pm Post subject: Re: Distributor Seems to Retard on its own.... |
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| Chinaclipper wrote: |
OK yesterday I did exactly as suggested.
I set idle to 800 rpm (wow)
I plugged vacuum on side of carb, and set timing with the light to 7.5° BTDC
I ran it up to 3000+ RPM and saw with the light a nice 30° advance! I tried to film it but it just didn't seem to like it. the camera wouldn't show it.. hmmm.
Checked it at idle (800rpm) again and it was right there at 7.5° BTDC.
So all good.
I will try it out tomorrow; and re-check after .
Today and yesterday there was just too much other distractions, and it was raining.. yuck... |
As long as you revved it past all in advance, that sounds perfect. |
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Chinaclipper
Samba Member
Joined: October 03, 2019
Posts: 810
Location: Somewhere in the great Midwest
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| Posted: Thu May 29, 2025 6:26 am Post subject: Re: Distributor Seems to Retard on its own....SOLVED |
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Well, yesterday I just had to give 'er a try.
I checked the timing again, with the light and as per instructed-800 rpm, etc- before I started out:7.5° BTDC; gremlins didn't come in overnight and change it, so that's good.
Started her up, and drove it around for 30 minutes. Went again mostly city streets, ie 35-40 mph, but did get it on the parkway and had it up to 55 mph a few minutes. Truth be told, that 800 RPM idle seems really low. She burped a bit when it was just starting out. (Wx was about 55° F in the afternoon and cloudy.) After she was warm tho, no skips or stutters off the start, no hiccups, no issues.
So, got her home, and of course, I had to check the timing again-with the light, vacuum off- etc etc yada yada yada...
7.5° BTDC. WIN
So, I will call this a win, thanks everyone for the help. Dunno why or how just yet, I suppose it is a combination of a few things but I'm not looking a gift horse (bug?) in the mouth.....
Maybe I could bump up that idle just a bit tho.. After I timed it correctly, of course....
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bsairhead
Samba Member
Joined: October 08, 2008
Posts: 4486
Location: viroqua wi.
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| Posted: Thu May 29, 2025 6:40 am Post subject: Re: Distributor Seems to Retard on its own....SOLVED! |
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| Head scratching, you change the vac line? Or perhaps get it on better or add a drip leg? I am glad your good just wondering what the original snafu was. |
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heimlich
VWNOS.com
Joined: November 20, 2016
Posts: 7499
Location: Houston, Texas
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| Posted: Thu May 29, 2025 7:16 am Post subject: Re: Distributor Seems to Retard on its own....SOLVED! |
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It was your idle speed. You had it set to high. When you get close to a 1,000 RPM the mechanical advance will kick in. If you try to time it there it will be difficult as you just saw.
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baldessariclan
Samba Member
Joined: October 14, 2016
Posts: 2037
Location: Wichita, KS
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| Posted: Thu May 29, 2025 7:29 am Post subject: Re: Distributor Seems to Retard on its own....SOLVED |
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| Chinaclipper wrote: |
| Truth be told, that 800 RPM idle seems really low. She burped a bit when it was just starting out. (Wx was about 55° F in the afternoon and cloudy.) After she was warm tho, no skips or stutters off the start, no hiccups, no issues. |
The usual idle speed spec for your current engine/carb/distributor combo is 850 rpm +/- 50 rpm. So maybe try 850 rpm - 900 rpm for your idle speed -- see if you like that better.
And when all else is dialed-in and tuned correctly, any remaining sluggishness while the engine is cold suggests that you may need to adjust/increase the choke a bit -- you generally don't want your throttle lever dropping to the lowest point on the fast idle cam and choke completely open until the engine is fully warmed-up & at normal operating temperature.
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