A while back I had a problem with a hard miss on cylinder #6. I asked
for help and got good advice. Today, I finally got the car back on the
road and it is running better than ever. What I found wrong with it is
one for the archives for sure. [The story is sort of long, so if you
don't like suspense, skip to the last paragraph.]
Since its been a while, I'll go through the history first. It started
missing while I was driving ... like something broke. When I got home,
I pulled the spark plug wires [one at a time] while the engine was
running. The last two cylinders were dead [no change with or without
the plug wire]. A compression check indicated no problem. Next, I
sequenced through changing out the plugs, wires, points, condenser and
cap. During this exercise, I was able to verify a good spark. I
changed my attention to the back carb. Using a can of ether [spraying
it around the carb, I found air leaks at the carb shaft and at the
manifold gasket. After fixing these, I put it all back together with
great anticipation, only to find no change in the miss. The last thing
that I did was to switch the carbs front to back and visa versa].
Absolutely no change. Therefore, I now know its not the ignition and it
is not the carbs. The only thing that is left is to start tearing down
the engine.
Now here is where it gets interesting. When I pulled the rocker arm
assembly off, the #6 pedestal slid off the back. Sure nuff, the little
screw that holds the assembly together was missing. I figured that it
must have made it to the pan and wasn't looking forward to pulling
that. I pulled the head next, neatly stored the pushrods and started
cleaning it parts up, looking for anything broke. I expected to see
brunt valve, cracked head, or something else expensive.
Here's the punch line. When I took the #6 exhaust tappet out of the
hole, I found the rocker arm shaft screw inside the tappet. Somehow,
while I was driving, it had worked its way down and was captured under
the tappet. It wasn't big enough to keep the valve open, but at speed
it changed the duration enough to really mess up the timing on the #6
cylinder. So, all I had to do is buy a couple of gaskets and some
LOCKTIGHT for the screw.
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