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How to- Modify your Kadrons for SVDA!
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Lingwendil
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PostPosted: Wed Jun 15, 2016 2:23 pm    Post subject: How to- Modify your Kadrons for SVDA! Reply with quote

I have had a ton of people asking how I modified my kadrons for use with an SVDA. I was tired of vendors that either did it redneck style (JB weld and wire? No, thanks) or drilled the throttle plate, that is already hard to access once in a cramped engine bay wedged next to your fan shroud. I've posted this in the vintage kadron thread as well, but figured I would redo it for its own thread.

So here's my first tutorial!

First some pictures of the offending carbs. These were on the car when I bought it, and run great. They had a little stumble, and instead of just dealing with it, or richening up my idle and adding more accelerator pump squirt, I wanted to run a SVDA for better performance and fuel mileage, since I actually drive my cars every day...

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Don't mind my hacked up aircleaner, it was like that from superior PO engineering.
Here's how I modified them for SVDA...

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First strip your carbs down completely...

Use your drill and a file to turn a steel pin to fit the vacuum channel, and then cut it to about 1/8" long... it would be a good idea to first gauge the depth of the port to verify the plug is just as long as it needs to be, mine showed 1/8" to be perfect. You would probably be okay using a bit of brass or aluminum as well.

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verify that it will just barely fit in the hole, this ensures a tight friction fit, too tight and you may crack the area around the hole. Once satisfied with the size, drive it down the channel with a punch, making sure to only block the bottom port below the throttle, leaving the upper port clear...

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Get yourself a 1/8" drill bit, and drill out the port plug on the carb body, I did this while my carbs were apart and venturies removed, but you are only going into the plug about 1/4" before it spins out with the bit. Next, get some 3/16" tubing and cut and deburr it. I found for my carbs that 7/8" long worked great. Tap it in. Use a block of wood or the handle of a screwdriver so you don't mess up the brass. Peen the edges gently with a punch to keep it in place. You could use a tiny bit of loctite if you like, mine fit tight without it.

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I did both of my carbs and connected them with a tee. You can do fine with just modifying the left hand carb, although I find I get a smoother advance with less scatter if I run both. I am not running any sort of vacuum check valve or anything.

Here they are installed on a 1776DP. Hesitation is gone, fuel mileage is about 28MPG highway without being conservative with the gas pedal Laughing

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Feel free to ask any questions! This was only about 45 minutes of work once the carbs were off the car, and super easy if you have basic mechanical skill and know how to take your time with a drill.
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ve7kilohertz
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PostPosted: Sat Jun 18, 2016 6:19 pm    Post subject: Re: How to- Modify your Kadrons for SVDA! Reply with quote

Nice write up! Great pics as well.

I will just throw in my $.02 worth as I just went through this with my carbs. I found I had a better vacuum signal with just one carb modified, instead of 2 T'eed together, however mine is a DP1600. Also, if you have a core 28 PICT or similar carb, you can salvage the brass tube from it by gently applying a little heat with a pencil torch around the body of the carb right around the tube, and it will come right out with little effort, and can be gently driven right into the Kadron after it's plug is removed. If you do this, the little opening at the end of the tube, can be drilled out if you need even more vacuum.

Also discovered that the jets in the 28 PICT and 30, as well as 34/3 have the same threads, both idle and main jets, so check them out if you are messing with re-jetting the Kadrons. You may have some jets to play with if you have any old Solex carbs kicking around.

Cheers!
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PostPosted: Sun Aug 21, 2016 6:23 am    Post subject: Re: How to- Modify your Kadrons for SVDA! Reply with quote

Quick comment - Max Welton and Jeff Lain suggest plugging the port with a piece if aluminum wire and loctite it. Thats what I usually do. But it's VERY important to remember the bottom hole is the top hole when you have it upside down... Embarassed
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PostPosted: Mon Mar 27, 2017 6:10 pm    Post subject: Re: How to- Modify your Kadrons for SVDA! Reply with quote

Is there a way to check if vacuum port is clear after you drill out plug-i.e. spray something in it and watch it come out another area?
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PostPosted: Mon Mar 27, 2017 7:01 pm    Post subject: Re: How to- Modify your Kadrons for SVDA! Reply with quote

yes...just dont remember where...I think its one or more of the holes at the buterfly.
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PostPosted: Mon Mar 27, 2017 7:09 pm    Post subject: Re: How to- Modify your Kadrons for SVDA! Reply with quote

https://www.thesamba.com/vw/forum/viewtopic.php?t=396290&highlight=kadron+vacuum+advance

Max
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PostPosted: Mon Mar 27, 2017 7:58 pm    Post subject: Re: How to- Modify your Kadrons for SVDA! Reply with quote

Has anybody measured what kind of vacuum you're getting out of the port from one carb or both? Has anyone stuck a T on the vacuum line to the distributor and measured it?

On a German 034 SVDA distributor, the vacuum cans require 200mm HG of vacuum to advance fully.

Just curious.
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PostPosted: Mon Mar 27, 2017 8:38 pm    Post subject: Re: How to- Modify your Kadrons for SVDA! Reply with quote

Thank you
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PostPosted: Sun Apr 09, 2017 10:50 pm    Post subject: Re: How to- Modify your Kadrons for SVDA! Reply with quote

wcfvw69 wrote:
Has anybody measured what kind of vacuum you're getting out of the port from one carb or both? Has anyone stuck a T on the vacuum line to the distributor and measured it?

On a German 034 SVDA distributor, the vacuum cans require 200mm HG of vacuum to advance fully.

Just curious.


I can't remember the exact reading I got, and since I have a rather lumpy cam I'm not sure how helpful it is, but I seem to recall somewhere around 140mmHg or so with both fittings tee'd together.
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http://www.thesamba.com/vw/forum/viewtopic.php?t=649622

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PostPosted: Mon Apr 10, 2017 4:24 am    Post subject: Re: How to- Modify your Kadrons for SVDA! Reply with quote

On the first set I ever ran, I had a T to both sides and then tried to just one carb and did not see a difference. Once just run to one side anymore.
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PostPosted: Sat Oct 14, 2017 8:20 pm    Post subject: Re: How to- Modify your Kadrons for SVDA! Reply with quote

In a world of plebeians, be a patrician.

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Just put them back on (it's been a crazy year, but long story short I had the throttle shafts rebushed after a aircleaner caught fire) and now run them with a VJU4BR8 "040" distributor. Adjustable vacuum can, it can be adjusted for both sensitivity and total stroke. Killer combo.
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http://www.thesamba.com/vw/forum/viewtopic.php?p=8115884#8115884
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PostPosted: Sun Oct 15, 2017 6:06 am    Post subject: Re: How to- Modify your Kadrons for SVDA! Reply with quote

Did my left one as per your thread, no luck. Not enough vacuum to pull in any advance. Next step is to try a different distributor...
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PostPosted: Sun Oct 15, 2017 10:00 am    Post subject: Re: How to- Modify your Kadrons for SVDA! Reply with quote

I've experimented with using the vacuum can from an SVA (vacuum only) distributor on an SVDA body in the past with good results, but that's the realm of advanced skullduggery...
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http://www.thesamba.com/vw/forum/viewtopic.php?t=649622

How to- Modify your Kadrons for SVDA!
http://www.thesamba.com/vw/forum/viewtopic.php?p=8115884#8115884
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PostPosted: Sun Oct 15, 2017 10:42 am    Post subject: Re: How to- Modify your Kadrons for SVDA! Reply with quote

I would think the best mod to do this would be, remove them and install a set of 40 hpmx's and a better dist. I think your butt will be gladd you did. or build a addaptor to go under the carbs and use a ---- ---- -------- in between the carb & intakes, as well as a ------- -------- the ----- ---------.in the ------ thats totally sealed. I was wondering how a" ----- -----" would work on this app too.
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PostPosted: Sun Oct 15, 2017 11:04 am    Post subject: Re: How to- Modify your Kadrons for SVDA! Reply with quote

Lingwendil wrote:
I've experimented with using the vacuum can from an SVA (vacuum only) distributor on an SVDA body in the past with good results, but that's the realm of advanced skullduggery...

Thatīs actually not a bad idea on engines with low vacum signal. But you have to limit the vacum advance inside the distributor or it will be way too much.

WRT using vacum from 1 or both sides. On engines with a lot of lower rpm vacum (stock or mild cams) it is usually enough with signal from only one carb. With more duration say 284ish & up seat duration it is normally beneficial to get signal from both sides. But, remember to use hard lines. If you use a rubber hose the signal will fluctuate and get lazy too. It is also important that the tube has the correct I.D. Too small a tube will slow the reaction time down just as well as a too large tube.
Also, when you use the signal from both sides you can normally "stretch" the signal so that the vacum advance reduces in a more linear manner when you begin to get into the main circuit instead of it just takes a plunge when the butterfly opens past the progression holes.

T
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PostPosted: Sun Oct 15, 2017 11:26 am    Post subject: Re: How to- Modify your Kadrons for SVDA! Reply with quote

An SVA vacuum canister from say a 1969-70' 113905205T vacuum only distributor will advance a distributor up to 32* at 80mm hg of vacuum. If you mounted it on an SVDA and then add in the mechanical advance of the Bosch 0231 170 034 which is 20-24*, it would be way too much.

The Bosch 07 059 vacuum canister that's on the German Bosch 034 SVDA distributor usually advances the distributor 8-10* on my Sun distributor machine. I see the vacuum advance start to move when I apply around 180mm HG of vacuum and it continues to advance to max advance thru 230mm hg of vacuum.

One of the problems I can see happening is using the 'new' Chinese 034 distributors on these modified dual carbs. Some of these distributors are bad out of the box. The pivot plates don't advance smoothly or jam. The vacuum canisters are not consistent in what's required to move them or don't advance enough. They are just not a quality built distributor. Many are being sold for $50 dollars which tells you it's not a high quality part. I've sold many restored Bosch SVDA's to folks who admitted to "gambling" on the cheaper distributor. After struggling with it, they bought a restored German SVDA which cured their issues.
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Lingwendil
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PostPosted: Sun Oct 15, 2017 11:58 am    Post subject: Re: How to- Modify your Kadrons for SVDA! Reply with quote

Alstrup wrote:
Lingwendil wrote:
I've experimented with using the vacuum can from an SVA (vacuum only) distributor on an SVDA body in the past with good results, but that's the realm of advanced skullduggery...

Thatīs actually not a bad idea on engines with low vacum signal. But you have to limit the vacum advance inside the distributor or it will be way too much.
T


When I experimented with it before I used a bracket inside the distributor body (mounted to the points plate near the pivot arm) that could be adjusted to allow the total vacuum advance arm "throw" to be limited. I found that using a small needle valve on the vacuum line was sufficient to limit the pull on the can as well.

wcfvw69 wrote:
An SVA vacuum canister from say a 1969-70' 113905205T vacuum only distributor will advance a distributor up to 32* at 80mm hg of vacuum. If you mounted it on an SVDA and then add in the mechanical advance of the Bosch 0231 170 034 which is 20-24*, it would be way too much.

The Bosch 07 059 vacuum canister that's on the German Bosch 034 SVDA distributor usually advances the distributor 8-10* on my Sun distributor machine. I see the vacuum advance start to move when I apply around 180mm HG of vacuum and it continues to advance to max advance thru 230mm hg of vacuum


Like I said, advanced skullduggery Laughing

Back when I had my Sun distributor testing rig I did a lot of work figuring out some combinations that work well, but all required some ingenuity to make them useful.

wcfvw69 wrote:

One of the problems I can see happening is using the 'new' Chinese 034 distributors on these modified dual carbs. Some of these distributors are bad out of the box. The pivot plates don't advance smoothly or jam. The vacuum canisters are not consistent in what's required to move them or don't advance enough. They are just not a quality built distributor. Many are being sold for $50 dollars which tells you it's not a high quality part. I've sold many restored Bosch SVDA's to folks who admitted to "gambling" on the cheaper distributor. After struggling with it, they bought a restored German SVDA which cured their issues.


The newer "034" type Chinese copies are such a crapshoot (heavily weighted towards the "almost useless" category) that it's not worth messing with one for the money I've come to believe, even some of the "good" ones from Aircooled.net or Lowbugget! Some have very little mechanical advance, some have excessive mechanical advance, all have too much (sometimes unacceptable) timing scatter.The vacuum cans are also very inconsistent, some need a ton of vacuum (I've got one that takes over 300mmHg!) To advance correctly. I would only really fool with them if they were cheap/free these days, or use them to rob parts from.

I definitely agree with you on original German, always a much better choice, even a worn out German dizzy is more drivable than a Chinese copy. I sold my last restored 034 a year or so ago, and the guy that runs it now loves it.

My new favorite distributor is the VJU4BR8/040 for several reasons, but the fact that good cores have been cheaper than aluminum bodied SVDA/DVDA types, and the curve is so nice, they are a very good choice for such applications. They work pretty well with the 34-3 carbs too. Quality points, rotors, and caps are affordable and available at Napa auto parts. The adjustable bits are just icing on the cake.
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73 super beetle thread!
http://www.thesamba.com/vw/forum/viewtopic.php?t=649622

How to- Modify your Kadrons for SVDA!
http://www.thesamba.com/vw/forum/viewtopic.php?p=8115884#8115884
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