Backfiring through carb

[Chris & Ranae Procyk <procyk19@domain.elided>]

My 392 is backfiring through the carb,
big-time.

On it's first* trip
It ran great for about 15 miles and then
started stumbling.  Somehow it made it
the remaining 5 miles and then the 20
back home.

After it got home, it refused to start again.

After completely refurbishing the ignition
except for wires, it still ran like sh&t.
The timing is at spec, TDC on #8 cyl.
Every plug has a great spark.  (I have this
cool little neon light with a suction cup
for you windshield that you attach to
a sparkplug and see if it's misfiring).

So I took the carb primary apart, and found
that the power valve was blown.

Replaced that and the needle (just-in-case),
and it really idled and rev'd great.

We have a safety inspection in PA and
I hadn't got it stickered yet, and it could cost
me 200 beans or something if it broke
down and I got caught, so I saved the
road test for the trip to the inspection station.

That was a couple weeks later.  But I'd started
it a few times and let it run for 15 minutes or so.
Started easily and sounded great.

Of course, as soon as my wheel touched pavement
on the way to get it inspected it started running badly
again.  My wife said I was shooting fire out the tailpipe.

But they had it for a week and never got around to
looking at it.  They did put a safety sticker on it.
So we tried to get it back home.  We wound up towing
it.

Since I was still suspicious of the carb (or more specifically
the guy who repaired it-me-), I put the WM's carb on it.

And that's when I discovered the major backfire through the
carb. 

Which was no fun, as I was manually operating the choke
butterfly at the time.

So the timing's fine and I've shot fire out both ends.
Do I have a sticking valve??  This engine has only 6K on
a rebuild, but that rebuild was at least 10yrs ago, and
the fire dept. probably didn't put 600 miles on it in the
last two year.  I'm going to do a compression check
later on today.

It ran like a champ when I test drove it, has run great
everytime we had to move it around the yard, so I
can't imagine a burnt valve. 

*The actual first trip was a  (very illegal) 40mi trip late
last summer (You didn't expect me to put an expensive
7+ft counter top in the 5' WM bed, when I had an
8-footer in the back yard??  I know, "the law is the law, son"
-love that commercial- but this vehicle only had a few
hundred miles since its last safety inspection, and if I
hit somebody there was no way the insurance company
would be able to figure out which IH it was, so the
"hitees" would get paid.  Promise I'll never do it again).
It ran awesomely then.


'67 1000B step-side p/up  BG241 + 4spd
'70 1200D 4x4 Travelette 392 4spd (going nowhere at the moment)
'71 1010 Travelall  392 auto
'73 1210 Wagonmaster, 392 auto (wants it's carb back)