Ignition timing and carb adjustment on 73 superbeetle

[SuperBeetle08]

Hey guys, just recently got my recently purchased 1973 super beetle with a 1600cc motor running, confirmed I have a DVDA distributor with a part number of 113905205an and 0231167070,and a EMPI 34p3 carb (the previous owner installed while trying to get it running),( I found broken nylon rider on points and got it running). My problem is, after adjusting idle setting on carb according to the John Muir book and a vw service manual by Bentley publishers, it still has a poor idle and I have a severe studder/miss while shifting gears or releasing the clutch, next I was going to set the timing according to these books with my timing light(strobe), am I overlooking something, or would setting the timing cure my issue? According to John Muir, the vacuum advance distributors are junk and he prefers mechanical, I am not opposed to putting a mechanical advance distributor in there, a good parts source would help, thanks for the help

[allsidius]

[ashman40]

Proper order for tune ups is to set the idle speed before the timing. This is because most stock timing is at an idle speed of 800-950rpm. Higher than this and the mechanical advance starts to kick in and will change the timing. Once dwell and timing are set the carb is readjusted to set the most efficient idle mixture and to readjust the idle speed if necessary.

If you are not sure if your distributor is working properly, test that both the vacuum advance and vacuum retard are working:

Before we start, adjust your dwell/point gap as this has an affect on timing.

With the engine running at idle... connect your timing light and take a reading. This is your original timing. If done correctly and everything is working, you should see 5ATDC with at DVDA distributor (the timing mark ccw from the TDC mark).

Once you have this baseline timing, disconnect both vacuum hoses at the distributor end and plug them so there is no vacuum leak. Take another timing reading. We will use this baseline for determining if your vacuum timing is working. You may need to adjust the idle speed using the large bypass screw on the left side of the carb to bring it back into the 800-95rpm range.

Now, one of the hoses from the carb will have vacuum at idle. This should be the vacuum retard hose connected to the rear facing port on the carb. This will be our test hose. Temporarily connect this hose to the vacuum advance port on the distributor. This is the port on the outside of the vacuum can. When you do this, the idle speed should increase and you should read an additional 5~8deg of vacuum advance (the TDC mark on the crank pulley should move ccw under the strobe light). If the distributor advances and stays advanced, you have a working vacuum advance.

Now move the hose to the vacuum retard port on the vacuum can. This is the horizontal port on the inside of the vacuum can. When you do this, the timing should retard form the previous baseline. You may need to adjust the idle speed back to the normal 800-950rpm. The TDC mark should move 11~13deg cw under the strobe light. If so, you have a working vacuum retard.

Now, disconnect all hoses from the distributor and connect just the vacuum advance hose from the port on the left side of the distributor to the vacuum advance port on the outside of the distributor vacuum can. There should be no change in the idle speed or the timing as vacuum advance is connected to ported vacuum which only comes in after the throttle is opened. At this point your timing should be around 7.5BTDC.

Next connect the vacuum retard hose to the remaining port on the vacuum can. You should see the idle drop and the timing retard. Readjust the idle to 800-950rpm and then set the timing so the 5ATDC mark lines up with the case split.

Now your timing is set... you can now adjust the settings on your carb.
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AshMan40
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'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

[volksnhousin]

You can try running your DVDA distributor as a SVDA by removing the hose that goes to the retard portion (port that faces towards the engine on a DVDA vacuum can). After removing the retard hose plug the retard port on the carb and just leave the port on the vacuum can open.

This will take away the spark retard at idle and may help your engine run better.

Just something to try.

[SuperBeetle08]

Ok, I performed all the tests you described, advance and retard seems to be working fine, set timing at 5 degrees ATDC, the car almost runs worse, I couldn't even make it to the road to test. What am I doing wrong? I even removed the carb to see if it had any crud in it(which it doesn't) and its a new carb. I should say the idle did pick up slightly but once you rev the car up and finally release the clutch to roll, it sputters and craps out. Another thing I should mention is, I haven't adjusted valves or changed, cleaned, or gapped plugs. Am I jumping too far ahead? Should I check those before I go any further? Another thing is that I feel like I hear a vacuum leak, I'm not too familiar with these engines, I'm not sure if it's the fuel pump making noise or if I have a leak, checked all vacuum lines, all ok. Any advice is greatly appreciated.

[HRVW]

Many people with limited experience (mostly their own) so to make things easy go the single vac route.

The Dual Vac was for the Calif smog to start with while VW did return to the single vac later on.

Remove the retard (lge hose) and plug off the lge nipple on the carb front side (towards you) with a plug (hose).

Assume that it's a single and set timing to 7.5 degrees before TDC.

[mhebb123]

I had a similar problem and went to a larger main jet (127 I believe). Runs great now, but I also have a 009 distributor.

[Blue69Baja]

Most of us that tune our own cars and have become good at it know how the car should Idle with the ball park adjustments....

If you are having trouble getting the Volume to control the rich/lean or the By-pass adjust to make the rpm increase then you are experiencing a vacuum leak or carb problem, that is if you have the dwell and idle timing close..

Volume adjust/mixture preset at 2 1/2-3 turns out (small screw below the big one.) Usually the engine will settle within 1-2 turns in or out...Rich running rough or lean running rough...

By Pass adjust for Idle speed....engine idle speed will respond to this setting as if you are moving the throttle arm, for this adjustment....
I usually preset it to about 1 turn... You may have to adjust it 1/2 turn, start the engine and see if it will increase in rpm enough to let your finish adjusting... Repeating the 1/2 turn until the engine will continue to run.

Throttle/idle lever adjustment.... Set and do not adjust.....Those of us that have properly running carbs know that we do not need to adjust this after the initial adjustment. I have 5 34's that run the same on the same engine... Bocar and Solex.

Remember that timing and dwell will change these settings, so get the timing done then finalize the carb Volume and By-pass...

Finalizing the carb adjustments Volume and By-pass will take some small adjustments to get idling right....A little rich on the volume is best to keep the engine from running too hot when idling.


http://www.vw-resource.com/tune-up.html#idle

Jim
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69 Baja with a 1914...
72 Super 100% orig...W/ factory air... 56,000mi
Even the spare is original..