How do I lock distributor advance?
 

Hello all,

I'm going to be installing a timing computer and need to lock the advance in my current dizzy (74 2.7 diz with both mechanical and vacuum).

I can figure plenty of ways to do it but I was wondering if there is a generally approved method. Should I remove the advance weights? Here is what I have considered:

Drill and tap holes through the advance plates and put in a screw. This would allow you to undo it if you ever wanted to but i'm a little worried that there isn't a lot of thread to bite on.

put a couple of spot or jb welds on the plates. this would certainly hold. but it's un doable.

any suggestions?

Don't do it.

Sure, the 935 had a locked advance but it spent most of its time between 4000 and 8000 rpm, at which point all the advance was in anyway.

The problem is that the rotor MUST move in order to prevent the spark from jumping to the wrong terminal on the cap.

With a timing computer you run a very high amount of static timing and the computer dials in variable retard to give you the curve you want. The trouble with this is that at max retard, such as when starting the engine and low RPM, the rotor is pointing at the next cylinder in the firing order. This coupled with a high-voltage ignition could cause misfiring and I wouldn't do it for a street car.

Look at the 3,2 Carrera and 3,6 dual-plug distributors-- all of these had an advance mechanism that didn't control the timing, but allowed "phasing" of the rotor so it was in the correct position to be fired by the control unit.

you can just zap the counterweights to the stator plate with a tig. We do it for the chaps at Motec all the time.

regards