On a Bosch distributor 0 231 142 005 that has the vacuum advance unit with an advance and a retard connection , if a weber carb conversion has been done is only the advance connection used ? From what I can find the retard connection comes from an emission control part that isn't used after the webers are installed?

Can the distributor be used without the Transistor switching gear under the battery tray? If so what changes need to be made?

Thanks,
Dan

Since we don't care about emissions, we should just care about how it runs. It is going to run best the way it was designed. If you get a 68 280S distributor with only advance and use that motors timing specs it might work. Otherwise nothing about the carbs change what the distributer is doing.

The best solution to the ignition box is the conversion I posted earlier, but it is pretty simple to make the dist you have work like the 68 280S one without transistor box. Get rid of the two .6 and .4ohm ballast resistors and replace with a single one with .9ohms. You will also have to replace the coil as the points won't take the current the transister coil runs on. Use the ballast and coil from a 68-69 model.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Dan:

Correct. The Webers only use vacuum advance and it is true s-port vacuum. As I remember, the vacuum with the original carbs was below the throttle plate which would make it more of a manifold vacuum which then worked on the distributor via the switching 2/3 way valves etc. When I put Webers on my '71 I only blocked the retard port on the distributor advence/retard unit to keep the crud out. The vacuum line runs from the front Weber directly to the distributor advance nipple. None of the "smog" vacuum/2 and 3 way valves, etc were working anyhow.

For the ignition side I replaced the points with a Crane xr700 and a crane coil. I thought about wiring around the Transistor switching gear but after figuring out I would need to get another coil plus some resistor changes and I would still have the point set I just opted for the Crane.

In my case, after the Weber change and when I figured out the logic behind the "smog stuff", I reset my ignition timing to 10 degrees BTDC. That made a big difference in performance and overall running. I have been as high as 14 degrees BTDC but ran into a pinging problem when the ambient temps got close to 100 degrees so I backed it off to 10 degrees and left it there. It appears to me (my opinion) that the "book" setting of 4 degrees ATDC only functions well if both the advance/retard is working as are all of the switches/relays/valves.

Just what worked for me. As they say ".... your mileage may vary ...".

Dan in Tulsa

__________________
Dan Taylor/ Tulsa, OK MBCA
'84 300D/'90 Jaguar XJ6/XJ40