[Healeys] ignition miss

[Brits'n'Pieces (Eric Frenken)]

Hello,

a friend of mine has a BJ8 with stock engine (but Getrag gearbox) but
Mallory distributor without vacuum advance. When he runs the car between
2,000 and 2,500 rpm and starts to slightly accelerate his engine starts to
misfire. It feels like as if someone switches off ignition for a split
second and the car misfires.

There's no problem running the car in either speeds below 2,000 rpm or above
2,500 rpm, full acceleration, steady speed or deceleration. He had his carbs
adjusted and synchronized but this did not change the situation.

Yesterday we put a new coil (high performance) in. This made the problem
even worse. Afterwards we exchanged the Mallory distributor against an
electronic ignition (123ignition), but forgot to connect the vacuum line on
our first test ride (vacuum line blocked by a screw). The ignition misses
were still there but they were not as bad as on the test drive with the
Mallory. On our last test drive we had the vaccum hose connected and we
nearly had no miss anymore. On his drive back home (2 hours drive) he still
had some few ignition misses, but not as many as with the old setup.

His ignition cables are new and look good. Does anybody has an idea what
these misses can be caused by?

Thank you.

Eric
Heinsberg/Germany