Ignition System guide.
The ignition system is a Lucas coil & breaker system, although the vacuum advance is provided, it was not used on any other than the 1st DB2s with 105 hp, it shouldn't be used at all now.
Starting with the distributor, this is a Lucas DVXH6A, rotating clockwise viewed from above, this Distributor is quite reliable if in good condition & if it uses good quality points, condenser and Reliable Red rotor arms of the correct rotation.
The distributor itself as fitted to Aston Martin's from 1950 to 1959, with 40 years of development (since Chris started at Four Ashes) we have found there is much do to do.
Firstly there is too much advance in its automatic centrifugal system.
Using our fully rebuilt 1950s Sun Distributor tester, we often see crank advance figures of 45 - 48°, this, coupled with a dynamic advance at idle of 10 - 12°, makes for advance figures of around 60°, no wonder these angines had a reputation for being a little frail !
The ideal advance at idle is 12 - 15° circa 800 rpm with a max of 36-38° @ 4000 rpm.
To do this you have to strip the distributor, alter the base plate outer stops (not alter the bob weights or push a copper tube over the stops !, this is what some distributor specialists do) to a pre-determined amount, the distributor then has to be rebuilt with new bushes or bearings (as required), then tested & the advance curve checked, specially made new springs fitted if necessary to get the right curve, re-tested & finally signed off.
For more info see DB2 to DB2/4 MkII Rebuilt Distributor's or DB MkIII Rebuilt Distributors.
The distributor is correctly fitted when the vacuum advance bulb is pointed to the rear & the aligned with the crankshaft.
There are two types of distributor capsare fitted to Feltham Aston engines, top entry with acorns & the orginal side entry type, the side entry cap should have the lead exits out toward the spring alloy tower otherwise you have a Jaguar one.
Ignition leads were originally the copper cored type with screwed on caps, however these are now illegal and offer poor performance compared with Magnecor performance ignition leads, these leads are the best we have used.
The DB2 coil is a DLB101 or screw in acorn equivalent, is really fitted in the wrong place as it takes heat from the rad, however it remains dry in its position right under the oil breather, the MkIII is better, a DLB 105 sports coil can be used.
Make sure that the coil is connected correctly with the - to the ign feed & the + to the distributor if its positive earth & + to the ign feed & - to the distributor if its neg earth.
Make sure the coil top moulding is clean & dry of oil & dirt, check the windings for resistance using a multimeter, this should be
The points gap should be 0.012" or 30 to 34° dwell if using a meter, checking the points condition can be done with a digital multimeter set to DC volts, connect the to the wire into the distributor & the distributor earth with the points closed - the reading should be less than 0.2volts, doesn't matter whether its neg or pos as it still reads correctly.