The Stovebolt Site Forums The Shop Area Engine Shop backfire thru carb

Just checking my sanity here, would a backfire thru the carb be timing? and it only happens under load on occassion.

A little hard starting is it? Ya got the timing advanced to fur! use a timing light and set it where the factory spec say to set it.
Denny Graham
Sandwich, IL

could be an exhaust valve sticking. i have found that an old engine
will build up crud on the valve stems at heavy load they tend to open just a little further than at idle and stick for a fraction
of a second. i would pull the cover rotate the exhaust valves
open one at a time and tap them (not frail )with a hammer they
should have a live hollow sound and the hammer will bounce.
if they sound dead they are sticking some good pb blaster and a little taping will free them up if they aint bent

Is it a backfire (loud bang), or like a cough with a hesitation?
If it like the latter, it could be a too lean fuel mixture.

Builder;
It does the latter, a cough, engine starts right up. The Rocjester B was rebuilt and does not leak (yet) and the accelertor pump gives a good shot down the carb and the heat flapper valve works correctly. I am wondering if the #1 or #6 cylinder get a little lean on occasion

BIG difference between "backfire thru the carb" and a cough or hesitation. I've been going thru the later with my stock 1950, 216 with a 'B'. The general consensus seems to be running the engine to cold, especially since the weather has turned on us. I have a 160° stat in there now and the suggestion is that I run a 196° and see if the stops the hesitation, I haven't gotten around to it yet.
Philip, if it were a stuck, burnt or carboned up valve a backfire thru the car would present itself all the time, not just "it only happens under load on occasion". That would indicate timing. A hesitation or cough as xx re-described would most likely be a fuel problem.
Denny Graham
Sandwich, IL

mine was popping and backfiring thru carb. turned out i hadn't properly retightened rockerarm assembly after replacing bent push rod due to stuck valve. it took some running for it to work loose but was immediately obvious when i removed the valve cover.
it was only doing it occasionally at first got worse as the bolts loosened up.

try replacing your condenser, and when you charge your battery disconect your battery cables