Well, I don't claim to know much about MGs, even though my son has a '71 B,
but like a few others, I'm gessing it's a timing problem. #1 plug is firing
near the correct time; #2 is firing enough to keep it dry but is so early the
intake valve is still open a bit (that gives the backfire thru the front
carb), so it doesn't contribute much to running the engine. The other two
plugs don't fire at all, since the pistons are in the middle of their intake
or exhaust stroke with a valve open.
The timing chain/gears could be worn enough to have allowed the chain to skip
a tooth. Another post described how to check for correct valve timing.
Or, the distributor drive gear is not correctly meshed with the cam. Could
be just a tooth (or maybe two) off, or is 180 degrees out. Either is a
mistake easy to make. Again the previous post described the checking
procedure. I doubt that it's simply bad ignition timing, since it's not
likely that turning the distributor to either extreme would kill two plugs.
Of course, all this assumes that the plug wires are installed correctly.
There...I stuck my neck out. Sure will be fun to learn what the real problem
was!
Phil
|