I have a 1964 MK2 3.8 MOD 8:1 compression. I am installing a 123 ignition JAG 6-R-V unit. I have read as much as I can find about the subject of maximum advance. I plan to start my engine in the next few days after its rebuild. The engine was run-in briefly (not on a rolling road) with the 123 unit with no vacuum connected. It is currently on the number 2 clickable setting. Now the engine is back in the car. New coil, new plugs, new ignition wiring etc.
My question revolves around the subject of the source for vacuum advance. My engine rebuilder has come to the conclusion that it is manifold vacuum that should be used rather than carb vacuum, although the 123 installation instructions specifically indicate the use of carb porting.
I have done some follow-up research and I found one article that advocates for the use of manifold vacuum to be pretty convincing. I have attached the article for your review.
I am interested in thoughts and comments from the group.
Lin
http://chevellestuff.net/tech/articles/ ... nifold.htm
Hi
I am in a similar dilema. I have a Mk1 Sprite (frogeye) with a 948 8:1 compression engine (it is not original and has no number!). The engine and carbs have just been rebuilt and runn in. I bought a 123 dizzy (with vacuum), new coil, plugs etc. Having fitted everything and timed statically I drove to the garage to have the timing set up. They claimed to have experience with 123s. The car is not running great. Idle is fine but it misfires sporadically. The vacuum takes off the manifold and there is no vacuum port on the carbs (H2s). I have since read in two places that the 123 does not work with manifold vacuum.
The service and info I have received from 123 is really poor (like everyone else says).
I don't know what to do now!
Am interested in what your experience is.
