Vintage Cars: W114, ballast resistor, rotor arm


Question
I bought a 1976 W114 250 mercedes 2 years ago and it has just spent 2 years undergoing a slow, but relatively minor restoration (mostly bodywork and interior).
It had an LPG conversion done on it from previous owner, and was probably not run on petrol for many years.

Recent work includes:
(New Points, Plugs, dist cap, leads, ignition coil)
Rotor arm, condensor and ballast resistor are just purchased and are about to be fitted.

Problem is, she revs fine when not in gear, but once she is in gear, she just doesnt pull well at all (when run on both petrol or LPG).

Mechanic thinks it is an electrical fault.

Have you any thoughts on what problem might be?

Answer
sounds like timimg to me, set dwell  ( around 40 degrees) ( with meter if you have it) and then set timing with light, advance it a bit and see what happens. Start with 4 degrees ATDC with vacuum attached
have you done valve lash?  This could also be cause.
Then there are the carburator issues  .  Start here first

Have you pulled a plug, what do they look like, more info you can give me the better.

Good Luck
Ron