Posted by Sherman in Idaho [108.162.246.24] on Saturday, October 08, 2016 at 17:57:08 :
In Reply to: Still no luck posted by Andrew Walak [108.162.219.160] on Saturday, October 08, 2016 at 15:34:54 :
That's the basic troubleshooting approach for any tricky problem. A 62 is mighty simple to begin with, so it's hard to get much simpler, but if you have any sort of known-good parts to swap in, that would help. Fuel supply upstream of the fuel pump can be eliminated by a hose stuck in a jerry can strapped to the running boards or in the bed. Distributor advance can be disabled. A velocity governor can be bypassed and the linkage hooked direct to the throttle. None of these is trivial, but you're already into non-trivial stuff like rebuilding the carb.
Backfiring suggests timing issues to me -- valve or spark. Could it be as simple as a sticky valve that closes while cranking (I assume you did a compression test, no?) but doesn't close fast enough at driving speed?
Hard to watch the carb for fuel flow while under load but if you had a fuel pressure gauge you could cobble in right at the carb inlet that might tell if the system upstream isn't keeping up.
It's got to be something simple, of course, and thankfully the problem isn't subtle or intermittent, but it will still take some troubleshooting to find it.