[Healeys] M spec ignition questions

[Hap Polk]

Adam,
My two cents. I think Jack Aeckerlin got it right. If period correct looking
performance is your key goal, the 123/GB electronic distributor is the best.
It has electronic "points" and user selectable electronically controlled
advance curves in a high quality housing. Quoting Jack " The 123 ignition is
by far the best electronic ignition. Rally drivers all over Europe use it
now." See www.tdcperformance.ca. Other good choices for racing are the
Mallory distributor sold by Denis Welsh and a rebuilt Lucas distributor with
a Pertronix Ignitor Hall effect sensor instead of contact points. Then there
are distributorless systems...

As for the drive gear/dog shaft, in theory a worn drive gear and/or dog
should have little effect as the gear and dog are loaded by the
distributor's rotation inertia and friction so that the driven gear and dog
faces remain in constant contact. But the new pointless distributors have
less rotational inertia and friction than the old points and advance weights
distributor making it easier for engine and road vibrations to cause the
distributor gear tooth and/or dog to bounce around to the extent allowed by
gear and dog slop. So for racing, a new distributor drive may be helpful.
Speculating, adding a little vibration absorbing compliance and frictional
drag by inserting a elastomer bushing between the distributor shaft and
housing might reduce ignition timing flutter at speed. 
Hap Polk

-----Original Message-----
From: healeys-bounces at autox.team.net [mailto:healeys-bounces at autox.team.net]
On Behalf Of Adam Nolde
Sent: Sunday, February 06, 2011 9:08 AM
To: Healey List List
Subject: [Healeys] M spec ignition questions

All,

2 questions:

1) what is the best distributor / electronic ignition combination to operate
my
10:1 compression M spec 4cyl Healey race car?

2) should I order a new drive dog or drive gear?  or will an older used one
be fine?  how much play is OK?

adam