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14platoon
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PostPosted: Sun Jul 05, 2015 5:37 am    Post subject: Timing Reply with quote

1800cc dual carbs stock set up, vacuum distributor.

Can anyone explain why I need to strobe time at idle and then at advance, won't this mess the idle that I just timed?
In the Bentley manual this gives settings for advance and retard,how can you set the timing for both?
Despite extensive reading, I'm still confused. Which should I set it at?
Ps I did a search, couldn't find my answer.

Thanks
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Bleyseng
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PostPosted: Sun Jul 05, 2015 6:58 am    Post subject: Reply with quote

Time the engine at max advance which should be 3500 rpm to 28 degrees, hoses off. You have a vac only distributor? If so find a vacuum and mechanical advancing distributor as used stock for better timing.
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PostPosted: Sun Jul 05, 2015 9:17 am    Post subject: Re: Timing Reply with quote

14platoon wrote:

In the Bentley manual this gives settings for advance and retard,how can you set the timing for both?
Despite extensive reading, I'm still confused. Which should I set it at?


Bleyseng is correct. The Bentley manual timing settings only apply to factory engines with factory distributors. So many parts have been swapped around over the years that we don't use those timing methods anymore, except to get the engine close enough to get started. Once it's running, use the 28* at 3500 RPM method, with all the hoses off.

What is the part number of your distributor?

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Wildthings
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PostPosted: Sun Jul 05, 2015 11:04 am    Post subject: Reply with quote

To time your engine at full mechanical advance you need the vacuum hoses removed and plugged.
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Tcash
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PostPosted: Sun Jul 05, 2015 11:05 am    Post subject: Reply with quote

This was for another post. But should give you the idea.
http://www.thesamba.com/vw/forum/viewtopic.php?p=7725441#7725441
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14platoon
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PostPosted: Sun Jul 05, 2015 11:58 am    Post subject: Reply with quote

Thanks for the great replies.
As soon as I get a chance I'll come up with the distributor number.
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14platoon
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PostPosted: Mon Jul 06, 2015 4:28 am    Post subject: Reply with quote

Image may have been reduced in size. Click image to view fullscreen.


I couldn't find a number on it but this is it.
Engine number
AW026007 if that helps.

So can I take it this is the idea

check for leaks
Check valves plugs and points gap
Set timing to TDC
set Carbs up by checking throttle valve opening and choke opening initial settings gap as per Bentley
sync Carbs
Adjust mixtures

Finally then re set timing by using the advance settings provided by the guys above

does that sound about right?
I'm assuming the throttle valve and choke valve settings apply to both carbs?
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PostPosted: Mon Jul 06, 2015 5:11 am    Post subject: Reply with quote

The number is probably on the rear side of the distributor so you may need a mirror.
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Wildthings
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PostPosted: Mon Jul 06, 2015 8:09 am    Post subject: Reply with quote

It is a SVDA distributor that you can time at 28 BTDC @3500+ rpms, hoses off. You don't really need any more info that that. The points, cap, and rotor for your year should fit.
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14platoon
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PostPosted: Mon Jul 06, 2015 11:06 am    Post subject: Reply with quote

Thanks for the info above, that will come in very handy later.

I have started at the basic settings, guessing that previous owners have fiddled around.
I found the throttle plate settings way way out as were the choke / fast idle settings, in fact the choke wasn't even engaging, hence the struggling to start on its own.
I have adjusted to specification the left hand carb including the fast idle setting and replaced. I haven't fiddled with any mixture or idle settings yet. What I have found is that now when I start (I tested it), it starts up much much better but is idling waaaaay too high and I can't turn it down at all, even screwing the main idle screw right in. Obviously I have only just started but can anyone answer why the idle can't be turned down? Have I adjusted the fast idle wrong, although I believe it was idling waaaaay too high when the choke should have snapped off?
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14platoon
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PostPosted: Mon Jul 06, 2015 1:34 pm    Post subject: Reply with quote

To clarify
My bus now idles really high but doesn't drop RPM when you hit the throttle, I'm confused ??
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PostPosted: Mon Jul 06, 2015 2:49 pm    Post subject: Reply with quote

If you are sure the chokes aren't holding on the high idle try disconnecting the throttle linkage and see if something's hanging it up, could also be leaks in the throttle shaft bushings or a hose left off. If you have reset your timing and the base is advanced from the previous setting you'll have to readjust the idle at the carbs.
Are you following this exactly and not skipping any steps? http://www.thesamba.com/vw/forum/viewtopic.php?t=399195
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14platoon
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PostPosted: Mon Jul 06, 2015 3:26 pm    Post subject: Reply with quote

I started with setting the throttle valve adjustment and choke adjustment as carb was off. Just put it back on to see what Dort of result I had, this was the left carb. I haven't touched anything else yet, no timing no mixture etc.

Ps, when I set the choke as per Bentley, it wasn't too clear. I set the. Choke / fast idle open to the specification but was on the highest the choke cam can go. Like this........
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Wildthings
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PostPosted: Mon Jul 06, 2015 6:20 pm    Post subject: Reply with quote

Is the choke opening? Maybe the PO had it set the way he did because the choke heating coil is burnt out.
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timvw7476
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PostPosted: Mon Jul 06, 2015 7:21 pm    Post subject: Timing Reply with quote

The Bentley settings are there to confirm your distributor is "behaving".
With the dual carb set up, the distributor had/has three functions:
1> Vacuum retard, working @ idle, you set the timing here, 10*ATDC,
hoping that the other vacuum advance can & the internal centrifugal
advance mechanism is GOOD.
2> Vacuum advance can, this one draws the timing well beyond 28* BTDC, (40*BTDC+) and is load sensitive. It gets plugged to check the third aspect of engine timing.
3> Centrifugal Advance, is under the point-plate, and moves the timing to
28* BTDC or so, gets checked with strobe light, @ 3,000+rpm.
The likelihood that an old distributor is capable of performing all this is
quite remote, most vacuum retard cans are blown/leaking, so if you
start at 10*ATDC, you may never arrive at 28* BTDC, the strobe will
simply betray where the spark is really going, so you have a chance to
fix it before you do any damage with persistently terrible timing, which
heat-soaks cylinder heads. Sad
P.S. I capped the vacuum retard, confirmed the vacuum advance side
of the can was still good, and set my 1800 @ 7.5*BTDC @ idle.
Worked just fine.
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PostPosted: Tue Jul 07, 2015 12:15 pm    Post subject: Reply with quote

I reset the choke onto it's stepped cam and now the chokes are working great, in fact the bus starts up better than ever before. I'm at the very early stages of the timing and tuning but something is bugging me.
Bentley states to set the timing, then adjust carbs afterwards. I know my carbs are way out, how will the timing be set correctly when everything is out, won't this give me false readings?
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Wildthings
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PostPosted: Tue Jul 07, 2015 12:52 pm    Post subject: Reply with quote

14platoon wrote:
I reset the choke onto it's stepped cam and now the chokes are working great, in fact the bus starts up better than ever before. I'm at the very early stages of the timing and tuning but something is bugging me.
Bentley states to set the timing, then adjust carbs afterwards. I know my carbs are way out, how will the timing be set correctly when everything is out, won't this give me false readings?


Set your timing at 28 BTDC at 3500+ rpms, hoses off and plugged. Your timing is good to go if set this way no matter the condition of the carbs or the engine in general.
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PostPosted: Tue Jul 07, 2015 1:25 pm    Post subject: Reply with quote

Thanks for the reply, seemed a bit confusing that part.
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PostPosted: Thu Sep 03, 2015 8:37 am    Post subject: Timing Reply with quote

To link to this thread
Code:
[url=http://www.thesamba.com/vw/forum/viewtopic.php?p=7808768#7808768]Timing[/url]


Tcash wrote:
The distributor should be lubed every 6K miles.
Lubing the Distributor


Tcash wrote:
Finding True TDC


busdaddy wrote:
When you finish adjusting the valves and have set the dwell read this before diving into the timing:

Here's the sermon Very Happy (you'll want to ignore the type 1 stuff)

First you need to determine exactly where TDC is on your pulley and then set the timing at speed like this: Here's my timing for noobs rundown (keep in mind this assumes you have a degree wheel, timing scale or dial advance timing light and know where TDC really is, if you don't understand the marks on your type 1 pulley read this: http://www.thesamba.com/vw/forum/viewtopic.php?t=251672&highlight=stock+pulley+marks ). Or if type 4 see this: http://www.ratwell.com/technical/FindTimingMark.html

If you only have one hose attached to your distributor pull it off, you don't need to cap it (no need on single hose systems), if you have 2 pull them both off but plug the one that was connected to the nipple facing the distributor (retard {not you, that's what the hose does}). Now connect the timing light to the battery and the #1 plug wire according to the timing light instructions (and set it to zero if it's the type with adjustments). Now start the engine and shoot the timing light at the scale and pulley (hold the light in your right hand), see the mark on the pulley?, good. Now using your left hand slowly open the throttle on the side of the carb or throttle body (move it the same way the cable pulls it) and watch the timing mark VS: the scale, the mark on the pulley should start to move to the left, open the throttle a little more and continue until the mark no longer moves to the left any more (yes it's loud, isn't it?), give it a bit more throttle just to confirm the mark is staying put at wherever it stopped (hopefully 28 degrees) and then release the throttle. If it stopped at 28 move on to carb/FI adjustment, if it went past or didn't make it all the way loosen the distributor clamp a little and turn the distributor a few degrees one way or the other (you pick, if it's worse go the other way), repeat until you find the happy spot and don't forget to tighten the clamp when you are done (make sure the distributor is pushed down all the way into the case too). Avoid loose fitting clothing and long hair near spinning fans and belts too, no need for a trip to emergency. Now put the hose back on, pack up the timing light and move on to carb or FI adjustment.


Quote:
http://www.vw-resource.com/find_tdc.html
From the TDC mark, measure 46.5 mm to the right on the rim of the crankshaft pulley. This is 30 degrees BTDC; mark this point also with white paint. This is the maximum advance point at 3500 rpm.


Tcash wrote:
The timing really should be checked in three places:
Set at idle
Check Mechanical advance at specified rpm's hoses off and plugged
Check Vacuum advance pulling specified vacuum with a vacuum pump
Check Vacuum retard hose off and plugged


Tcash wrote:
You need to determine which distributor you have by the part number on it and look up the specifications located in the Bentley.
Or here.
http://www.oldvolkshome.com/ignition.htm

As an example:
This is the specs for a Bus & Pickup Late 1976-1978 All States, 1979 Federal * 2000. Note the timing specs located at the bottom.

Timing specs.
Timing Set At:
7.5deg BTDC
@ 850-950 rpm (Man Trans), 900-1000 rpm (Auto Trans) w/strobe, vacuum hose connected
Advance/Retard Range:
Vacuum: 8.5-11deg Adv @ 7.9 In. Hg

Centrifugal:
8-13deg @ 1600 rpm,
20.5-24.5 @ 3400 rpm


TIMING SPECIFICATIONS T2
Image may have been reduced in size. Click image to view fullscreen.


Type I timing scale.
jamesdagg wrote:
Print, cut out and draw marks on your pulley where needed.
http://i43.tinypic.com/2cghs7c.jpg
Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.


Type I timing scale.
ashman40 wrote:

Print this diagram out at full scale. It should print out at 7" diameter.
https://www.thesamba.com/vw/gallery/pix/916242.jpg
Image may have been reduced in size. Click image to view fullscreen.


Type IV timing scale.
LeeE wrote:

Homemade Type IV timing scale
http://www.thesamba.com/vw/forum/album_page.php?pic_id=237878.jpg
Image may have been reduced in size. Click image to view fullscreen.


Properly aligned Type IV timing scale. Note how the 32* mark lines up with the fin on the fan housing.
the_benjamin_effect wrote:
http://www.thesamba.com/vw/forum/viewtopic.php?p=7810248#7810248
Image may have been reduced in size. Click image to view fullscreen.


Timing 68-70 113 905 205T


Last edited by Tcash on Wed Jul 26, 2017 7:48 pm; edited 4 times in total
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Tcash
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PostPosted: Mon Nov 09, 2015 2:49 pm    Post subject: Timing Factors Reply with quote

Ignition timing is at its optimum (sweet spot) when the spark from the spark plug ignites the air fuel mixture precisely at the correct piston position in the cylinder to produce the highest amount of work (peak power). Engineers design and use expensive equipment to test and establish this sweet spot under all conditions.

There are many factors that effect that sweet spot.
Bore and Stroke
Compression ratio
Piston design
Piston speed (rpm)
Combustion chamber design
Camshaft design
Induction system
Exhaust system
Air fuel ratio
Fuel atomization
Fuel octane rating
Operating temperatures
Induction air temperature
Humidity in the air

As you can see, there are a lot of factors to consider when setting the timing. Some if not all have been changed on our engines throughout the years.
Fuel is refined differently for climatic changes.
Ambient air temps and Humidity differ geographically.
Changes in Elevation affect the Air Fuel Ratio.
Some run low octane gas some prefer high octane gas.
Engine wear occurs with use.

So what are you to do. The one tool that we have at our disposal is a
Vacuum Gauge
https://www.thesamba.com/vw/gallery/pix/1422500.jpg

Timing with a Vacuum Gauge


Last edited by Tcash on Mon Nov 09, 2015 2:50 pm; edited 1 time in total
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