[Roadsters] KA24E missing?

[Paul]

  Last ice cream run, I hit a lousy patch of gravel road on a detour and
shook the heck out of my roadster.  Right after that, the KA started missing
at anything over easy acceleration and over 2800 rpms.  I checked the wires
to all the sensors and everything seems okay. 

  Today I changed the fuel filter thinking that a 40+ year old gas tank
probably had some crud shake loose, but the filter was clean.  And while it
was in the garage, I flushed out the cooling system.  Took it for a brief
ride, and it is still missing.  

  I pulled the plugs as soon as I got it back in the garage.  Oddly, 1 and 3
look perfect while 2 & 4 are clean, dry, but the top half of the insulator
is black while the tip is a nice clean ash color.

 

  Any thoughts what I should look for?  (Besides a R16 to put back in it!)

 

Paul

Ohio