In 71 the engine changed from an 18GK with a 25D4 41339 distributor to an 18V
584/585 with a 25D4 41370 distributor, so it all depends on what you have.
The characteristics of these were (all in crankshaft degrees):
41339:
Static 10 degrees
Strobe 15 at 1500 rpm
*Additional* centrifugal advance over the static figure:
10 degrees at 1000 rpm
24 at 2800
30 at 4600
Vacuum advance started at 7 in.Hg., ended at 13 in.Hg., giving a maximum 10
degrees.
41370:
Static 10 degrees
Strobe 16 at 1500
Centrifugal:
20 at 1850
35 at 3600
41 at 4800
Vacuum starts at 7, ends at 13, max 6 degrees.
At the end of the day without spending much time and money on a rolling-road
session and tuning the springs and weights of the distributor, multiplied by a
factor of several if you have vacuum advance as well, the best you can do is
run the most advance without pinking at any combination of throttle, revs and
load and not stalling the starter.
PaulH.
----- Original Message -----
I sent a query to Pertronix regarding the mechanical advance.
Pertronix confirmed that the Flame Thrower distributor for MGB's has
the following mechanical advance curve:
Engine RPM Advance, Crank Degrees
600 2 degrees
710 4
820 6
940 8
1100 10
1300 12
1550 14
1780 16
1900 18
2300 20
2610 22
3050 24
Henri
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