[Healeys] Which electronic ignition?

[Chris Dimmock]

Hi John,
I wasn't arguing with your comments re vacuum.
Maybe my Australian slang opening line was taken the wrong way?
Fair call= similar to fair enough, like good one.

If you just change the points for an electronic method of opening and closing
the circuit, on an SU/ Lucas system, then i don't see that you would change
how the vacuum aspect of the Lucas distributor operates. Or does it?? I don't
know.

My comment was that I have no idea what "type" of vacuum a replacement/
aftermarket distributor (Mallory, 123 ignition) distributor requires. Are they
designed to use manifold vacuum, or "ported vacuum"? Again, I don't know.
But I'd work it out before I just plugged it in.

Why did i raise this? Because I do know that if you connect the vacuum to the
'wrong' point - e.g if you connect a standard Lucas Healey distributor vacuum
line to the manifold of a Healey it will do exactly the opposite to what a
Lucas/ Healey distributor vacuum advance is designed to do.
Same if you connect a distributor that has vacuum advance designed for
manifold vacuum, and you connect it to the ported vacuum.

Hence the weber comment. How many webered Healeys have you seen with a vacuum
line from a Healey/ lucas distributor connected to the manifold? I've seen a
few. It won't work. It will provide the vacuum operated advance at the wrong
time. It will advance the ignition when the engine doesn't want, or need,
extra ignition advance.
Best.
Chris
Sent from my iPhone

On 17/04/2012, at 2:52 AM, John Harper <ah at jharper.demon.co.uk> wrote:
> Chris
>
> Yes I do know that the vacuum pipe into the distributor comes from a little
hole that is only uncovered when the carburettor butterfly is opened. I don't
believe that I said vacuum from the manifold but from the carburettor.
>
> I accept that one can afford to ignore this on race cars because in this
situation one is unlikely to run for long periods on light throttle.
>
> But my query still stands. It does not relate to Race cars but to standard
cars using original SU carburettors being converted to electronic ignition.
>
> Best regards
>
> John Harper