Hi, Willy...
Go to www.teglerizer.com
and click on MG Automobiles. Then click
on Distributor Advance Curves. Note the
differences between early and later
distributors, inclusive of the 23D mech.
type used on early 1275's.
Note the 24D dist. are the same model
numbers but, the serial number advises
the different advance curve within along
with the difference as to carb or manifold
ported vacuum "takeoff".
Essentially, the advance curves were
slightly different due to differences in
octanes recommended, compression
ratios, stroke of motor (1098), whether carb or manifold vac. ported,
etc.
The later emissions curves with manifold
vac. had "longer" mech. advance curves
so this needs to be watched in terms of
total advance so as not to go overboard
in this respect.
They are interchangeable to the exent
the motors will function (most especially
with vac. advance "plugged", using mech.
advance only) with the foregoing caveats
in mind.
(You may not get the motors "best" performance but it'll work.)
Generally speaking, the early dizzys with
short, quick mechanical advance rates
give the best performance in the 8.8-1
stock motors using "premium" running
32 degrees of total advance using carb.
ported vac. or vac. "plugged".
Cap'n. Bob
'60 :{)
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