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Fri Apr 12, 2013 2:26 pm

Hi all I have a svda distributor but can anyone tell me what the max mechanical advice should be (28 or 30) plus what should the overall advance should he with the vacuum line connected cause I have noticed the the total advance does go up with the vacuum line on. By the way the engine is a 1600 twin port with a 34 pict 3 carburettor. Cheers all

Fri Apr 12, 2013 2:29 pm

SVDA is a generic term... which one do you have?

Also they give a range of 28-32 because every engine is different. You need to try it and different settings and see which works best.

Generally you set the timing 28-32 BTDC @ 3500rpm with the vacuum line disconnected and the carb port plugged.

Fri Apr 12, 2013 2:43 pm

Hi what ive noticed is that when I set it to 30 btdc and then recheck it with the vacuum line on I get about 40 btdc and the idle timing at this setting with vacuum line on or off is 2 atdc. At this setting the engine will start but not as well as if I set it at 7.5 btdc, but the car does drive a lot and I mean a lot better with it set a 2 atdc with a max mechanical advance of 30 and a total of 40 (with vacuum line connected) have I done this right or wong?

Fri Apr 12, 2013 4:16 pm

Remove vaccum line and time to 28-32º BTDC when it is all in around 3500 RPMs. Note, but don't change the timing at idle (aka "iniital timing").

With the vacuum hose hooked up you should see 42-44º BTDC at 3500 with a light throttle.

Nobody drives at idle.

Fri Apr 12, 2013 4:20 pm

My Bosch SVDA: 30 BTDC @ 3500, 7.5 BTDC at idle @ around 900 rpm. Point and valves need to be right. It seems there's not much room for error with the 34p3 carb, but it can be done and run great with the SVDA.

Fri Apr 12, 2013 4:25 pm

Post up the numbers off the side of the dissy body.

Fri Apr 12, 2013 7:34 pm

Vacuum is an unpredictable variable when it comes to timing. It can change by engine load and even air temp. The only time vacuum is included in the timing "equation" is at idle on some distributors models (controlled engine speed with closed throttle plate).

Here are two different timing settings for two different SVDA distributor models:

Beetle 1974 * 1600 Federal Manual Trans (original VW distributor used for aftermarket SVDA designs)
Distributor: VW 043-905-205, Bosch 0231 170 034
Can Use: VW 113-905-205AL, Bosch 0231 146 101, VW 043 905 205 ZB (Mexico) (See Note Below)
Timing Set At:: 7.5deg BTDC @ 800-950rpm w/strobe and w/single vacuum hose disconnected and plugged
Advance/Retard Range: Vacuum: 8-12deg Adv; Centrifugal: 7-12deg @ 1600rpm, 20-25deg @ 3800rpm

Beetle 1970 * 1600 Auto-Stick Trans
Distributor: VW 113-905-205AD or AE, Bosch 0231 167 029 > 113 905 205AL, 0231 146 101
Can Use: VW 113-905-205AA, Bosch 0231 115 078
Timing Set At:: 0deg TDC @ 800-950rpm w/strobe w/vacuum hose disconnected and plugged
Advance/Retard Range: Vacuum: 8-12deg Adv; Centrifugal: 13-16deg @ 2200rpm, 25-28deg @ 3900rpm

Notice above the initial timing settings for the two SVDA distributors is different and the amount of mechanical advance is greater on the second one which helps explain why it has a lower initial advance. The second distributor is for an Auto-stick transmission which only has three gears. It requires a different timing advance curve than a manual tansmission. You need to pay attention to the model#s, there is no single SVDA timing.

The procedure of using a total timing setting of 28-32BTDC (initial + mechanical) is to make sure the mechanical advance does not over advance. Beyond ~3000rpm the turbulence inside the combustion chamber acts to reduce the time it takes for the ignited mixture to reach peak pressures. This means additional advance above this rpm is not needed. So a max (initial + mechanical) timing of around 28-32BTDC is all the acvw engine needs. Additional vacuum advance on top of this works as the load is decreased and the throttle opening closes... this closing of the throttle does two things, it leans out the mixture and increases the vacuum below the throttle plate. This increased vacuum causes the SVDA vacuum advance to increase the timing advance. This is just what the lean mixture needs.

Sat Apr 13, 2013 1:11 am

Right there seems to be two different answers here one lot of people are saying about 44 btdc total advance with vacuum line connected and the other the other group of people are saying 28-32 max advance with vacuum line connected which one is it?

Sat Apr 13, 2013 5:16 am

the old school 009 dizzy need to be set at 30 degrees BTDC at 3500 RPMs.

For the SVDA look at ashman's post. He has the listings right there. Look at which year you are and then set your idle timing with the vacuum hose plugged to what the listing says.

I have a 74 Super with a 1600 dual port. I have a 34 Pic 3 on my engine. With the SVDA set at 7.5 BTDC it runs great. I have 30 degrees max advance with no vacuum hose, and 40 degrees Max with the vacuum hose on.

Sat Apr 13, 2013 5:18 am

OK - you are not understanding correctly - the mechanical only section will give you about 20 or so degrees of advance. So - if idle is set at 10, then full advance with be around 30.

The vacuum advance is ADDED to this. So at full vac and mechanical, the advance will be in the 40s.

Hence - the correct procedure (assuming you have something like the "federal" Bosch Mexican SVDA) is to disconenct hose - set max mechanical (RPMS areound 3500) for 28 to 32 degrees. What it is exactly depnds you your particulars - my cars are either 28 or 30.

Your idle advance will be between 8 and 10 degrees. Now, if you idle is too fast, you may have some advance coming in already - so it may be 12 or 14 at idle. Readjust your idle speed to around 850 and then check it. Should be 8-10.

Does this clear it up?

Sat Apr 13, 2013 5:24 am

advinnie wrote: Right there seems to be two different answers here one lot of people are saying about 44 btdc total advance with vacuum line connected and the other the other group of people are saying 28-32 max advance with vacuum line connected which one is it?
28-32 is the timing numbers with the vacuum hose removed and engine at 3500 rpm.

44 is the timing number with the vacuum hose attached and engine at 3500 rpm.

When you set your timing you set it to 28-32 with the hose removed.

Sat Apr 13, 2013 5:37 am

Really just one answer here.

Set the max centrifical advance to 28-32º BTDC at around 3500 RPMs with vacuum hose(s) off.

Reatttach the vacuum hose(s) and at 3500 RPMs with a light load on the engine (max vacuum advance) , expect to see about 42-44º BTDC . THat will be the max total advance of centrifical + vacuum advance.

Let it loaf back to idle and set the idle speed the correct 850 RPMs. You are done, take it for a ride and report back.

Sat Apr 13, 2013 5:50 am

Right been out and done some checks in the pissing rain and this is what ive found. Right first the distributor is a 009 with a vacuum system fitted, the distributor comes from a company called AccuSpark.
With the engine at 850 rpm idle speed and vaccu line disconnected and pluged there is no mechanical advance at all compared to static timing (engine timming at this point is set at tdc)
At 3500 rpm the mechanical advance is 30 BTDC (so my mechanical advance gives me a total of 30)
And with vacuum connected I get 42 BTDC ( so the vacuum system give me 12)
This means I have no option than to set the idle timing at TDC cause if I do set it at 7.5 BTDC then add the mechanical advance then add the vacuum advance that will give me at total advance of 49.5 BTDC and I think that will be to much. What do you lot think?

Sat Apr 13, 2013 6:30 am

i think maybe ur carb is so outta wack that u cant get ur timing right...
mine was....u might try adjusting ur carb settings while adjusting the timing to help get things in order...
also sometimes the idle jet on the right side of the 34/3 needs opened a bit to smooth things out...totally fixed my bad idle.

Sat Apr 13, 2013 8:47 am

advinnie wrote: ... first the distributor is a 009 with a vacuum system fitted, the distributor comes from a company called AccuSpark.
Converting a 009 to SVDA. That's either ingenious, or wacked! :shock:

advinnie wrote: With the engine at 850 rpm idle speed and vaccu line disconnected and pluged there is no mechanical advance at all compared to static timing (engine timming at this point is set at tdc)
This is normal. Mechanical advance should start kicking in only above 1000rpm.

advinnie wrote: At 3500 rpm the mechanical advance is 30 BTDC (so my mechanical advance gives me a total of 30)
That's messed up. This demonstrates a lack of attention to detail on the part of the manufacturer. None of the stock Late Model Beetle distributors provide more that 28deg of mechanical advance (max variance). From a non-electronic engine control system point of view, 35BTDC is typically the max mechanical advance for a carburated race engine. Add the stock combustion chamber design along with carbon build up and maybe some oil leakage into the chamber... most aircooled VW engines should limit themselves to 32BTDC just to be safe.
The sad thing is the distributor should have been inspected at the factory and could have been adjusted to limit the range of advance (usually just a simple bending of a metal tab).

advinnie wrote: And with vacuum connected I get 42 BTDC ( so the vacuum system give me 12)
Typical SVDA vacuum can. What is more important is the amount of advance at a given vacuum. From what I have gathered the distributors matched to the 34Pict carbs require around 10-12 in Hg to reach max vacuum advance. Make sure you don't have one of the earlier (large can) vacuum canisters that max out at around 3.2 in Hg. These would be advanced all the time if connected to the vacuum advance port of a 34Pict carb.

advinnie wrote: This means I have no option than to set the idle timing at TDC cause if I do set it at 7.5 BTDC then add the mechanical advance then add the vacuum advance that will give me at total advance of 49.5 BTDC and I think that will be to much. What do you lot think?
Don't get too focused on the vacuum advance at the upper rpm range. This is where you will get your fuel economy and additional performance, but this should be self adjusting. If you dump the accelerator to WOT at 3500rpm the vacuum advance will drop off and you should have only mechanical advance until the vacuum rises again when the throttle closes. This self-adjusting nature is the main benefit of the vacuum advance. But this also makes it difficult to use as a measure of advance.
This is why you should pay attention to total advance (initial + mechanical). This is directly related to engine RPM. It is a good thing you checked the total advance and have dialed the initial timing back to make up for the extra advance coming from your mechanical.

Sat Apr 13, 2013 9:16 am

Thanks for all you replys people I will have to play around with the timing tomorrow andi will let you all know the out come

Sun Apr 14, 2013 10:49 am

Hello all right got two options I can set the timing at, but which one do you lot think is best.
1) set the max mechanical advance at 32 BTDC that gives me 44 max advance with vacuum line connected but the idle timing is at TDC.
2) Set the idle timing at 7.5 BTDC gives me max of 40 mechanical advance and 51 BTDC with vacuum line connected.
I can not set the idle timing past TDC cause the engine is really hard to start if i do but if you can start it it will run.

Sun Apr 14, 2013 10:51 am

If it were me with this funky distributor, I would go for a modified option 1 and set it to 30º.

Sun Apr 14, 2013 11:31 am

So set the mechanical advance to 30 max instead of 32 that would take the idle timing past TDC. will it hurt the engine to run the idle timing after TDC?

Sun Apr 14, 2013 2:34 pm

Nothing bad will happen with a TDC or even a few º ATDC when you go to start it.

Drive it and report back.