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

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