Mike,
You have done the right things so far. I had hoped that the problem was
going to be a fouled sparkplug, but you installed new and it continued.
Check the compression and the valve adjustment. While you are doing
valves, observe the action of the rockers. You want to see even motion
for all of them, not one that is moving much less than the others. This
is a visual check of camshaft. It's not precise at all, but will let you
know that there are eight lobes (or perhaps fewer) on the camshaft.
Here's a similar, current war story for you. A TD friend drove 50
miles at highway speed (4.3 rear gears) and all was great. On his return
trip there was missing, rough running, no power, etc.
Ignition checked out fine. Valve clearances were good. Visual check of
rockers was OK. Spark plugs were damp, heavily carboned from very
over-rich mix. Compression was 180, 170, 180, 30. Ooops. Off came the
head.
A chunk was out of the #4 exhaust valve. It _appears__ that what
might have happened is that a piece of carbon flaked off the piston head
(it was thickly coated, even though engine had only 1500 miles or so on
these pistons) and may have jammed under valve seat, causing it to burn a
piece right out of the valve. That finding was a great relief. After
all, it's just a matter of replacing a valve if the seat and guide are
OK.
In the case of this engine, it was obvious to me that the carbs had
been set way too rich, thus making the heavy accumulation of carbon on
plug and piston. And that causes me to wonder if the prolonged use of
the choke might have caused something similar in your engine.
Bob
On Tue, 27 May 2003 18:01:14 -0400 "Mike Razor" <mrazor@mis.net> writes:
> TD is still sick and can't seem to make it better. Been running just
fine until Sunday. Drove it about 15 miles and let it sit for the day
and got in it that
> afternoon, pulled the choke drove a few miles, pushed the choke in and
after
> about 3 or so miles it started missing, back firing, and would not
> do well under load. Would kick out some black smoke when it back
> fired. Made it to the little garage that works on any and everybody's
car
> and he housed it for the rest of the weekend.
> Today, the first thing was to free the starter, which has never
> stuck before, then we checked out the dizzy, readjusted the
> points, timing and idle. Drove it and still did the same thing,
> starts great, idles great but under load starts back firing and
> missing. Put in new plugs, readjusted the points, set idle and
> timing, drove it about two miles ran great. Brought the idle down
> from 1200 to 950. Left the garage got about 5 miles away and it
> started missing, backfiring under load.
> Any suggestions.
> Thanks!
> Mike
/// or try http://www.team.net/cgi-bin/majorcool
/// Archives at http://www.team.net/archive
|