Damaged SOMETHING with backfiring ...

"Jim Behning" > wrote in message
...
> On Mon, 16 Jul 2007 17:49:13 -0700, "Matt B." >
> wrote:
>
> >"Fred Mann" > wrote in message
> ...
> >> Well, I finally got my catalytic converter all the way off. I had to
cut
> >> the
> >> screws off with a dremel. Anyway, it's completely hollow. I'm not sure
if
> >> it's supposed to be like that. My concern is that the backfires blew
some
> >> of
> >> the "guts" of the CC down the pipe and possibly cause a clog there or
in
> >> the
> >> muffler.
> >
> >Shouldn't be hollow and yeah the guts could be plugging your mufflers.
> >
> >> Any thoughts?
> >
> >It's probably more than you wanted but could very well be time for a
> >cat-back exhaust.
> >
> Old post to answer too. If it is completely hollow then somone
> probably gutted it with a screwdriver. On my cars they tended to melt
> down and chunks would break loose. Those chunks either rattled making
> a noisy car noisier or the car would not run due to a corked up
> exhaust.
>
> The converter is supposed to look like a honeycomb. But the grid is a
> lot smaller than the honycomb you buy at the store to chew on. The
> holes might be .5 mm in size. Maybe it is a bit bigger but it is
> fairly small. You can hold a good converter up to light and see
> through it input to output. A failed one meaning one that has clogged
> or melted down will not pass light or you will see melted parts. Go to
> any parts store and ask to see a new one.
>
> Do not put a new converter on until your car is running perfectly. You
> will just destroy a converter in short order if the car is running
> rich, lean, or if the camshaft or ignition timing is significantly
> off. I prefered to get someone to attach a sniffing probe to the
> sniffing port to make sure the mixture was correct before installing a
> new converter. The procedure is in the Bentley. Since the converter is
> hollow you could just exhaust sniff from the tailpipe. The challenge
> is finding someone with an old style exhaust analyzer that will let
> you work for 15 minutes.


Well, it appears that timing was the main issue, so I adjusted it by trial
and error since there are no marks on the wheel or a pointer in the timing
hole. Anyway, I'm at about 85% full-power now. The engine still seems to
miss a little bit, but it's not regular.
I "fixed" the exhaust leak wih JB Weld and it worked fine for my trip
downtown. The leak was limited to a small piece of missing gasket.
The exhaust is a little smoky (sometimes not visible) and it kinda stinks.
I'd guess this could be due to my timing being a little off? Also, would the
converter help the smell. I'm certain that the fuel mixture has been
adjusted, so it's probably off as well.
Is there any way to test for proper amount of vacuum at the vacuum advance?
I don't see this particular test in either of the manuals (I have a Haynes
for this car and a Bentley for the older 79 Rabbit). If so, what should the
reading be? I hooked up a meter and it moved, but it may be beyond the
sensitivity of the guage. It read maybe 1 or 2 inches of vacuum when I
revved it up.
Just for the record, the car did not run as well with the catalytic
converter removed. Besides being obviously loud as hell, there was probably
an additional 10% power loss. I don't think I imagined it. So I guess a
certain amount of backpressure is necessary? Moot point I guess.
And here in NC, my car doesn't need to pass emission inspections, so I might
put off buying a new converter ...
I would like to formally thank everyone for their input. I read everything
and I really appreciate it. Danke schoen.