backfire

Did you have this diveablity problem before you changed the above mentioned parts?

I had a freak battery issue back in the 80's that caused the same symptoms, took a while to discover the culprit, replaced the battery and all was good.
 
Hmmm, I had exactly the same symptoms recently. Come to find out I had a cracked ear on the Zenith carburator which would expand when warmed up, allowing a healthy vacuum leak. Something to check anyway.
 
Original armored cable? They get squirrelly. Don't thread the ignition cable too far into distributor, it will cause a intermittent short by pushing the condenser bus bar into the distributor housing. These won't readily show on the amp meter.
 
Greg Jones said:
Hmmm, I had exactly the same symptoms recently. Come to find out I had a cracked ear on the Zenith carburetor which would expand when warmed up, allowing a healthy vacuum leak. Something to check anyway.
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Yes, Electrical or intermittent Electric/Ignition will Not cause backfires through Carb or exhaust.
-Unspent gas may -occasionally- be ignited in muffler but that's as close as it will get to anything remotely similar to a backfire. Odd backfires in muffler indicate electrical/ignition as the unburnt gas accumulates in the exhaust.

Carburetor and/or Vacuum leaks Will cause carb backfires.

jmho


moe


.
 
Say what? :confused:
Ignition problems WILL cause backfires in the muffler. When my repro ignition switch was making intermittent contact I had several loud explosions out the exhaust. It was louder than shotgun blasts.:eek:
Luckily my new Aries stainless muffler held together.:)
 
Tom Wesenberg said:
Say what? :confused:
Ignition problems WILL cause backfires in the muffler. When my repro ignition switch was making intermittent contact I had several loud explosions out the exhaust. It was louder than shotgun blasts.:eek:
Luckily my new Aries stainless muffler held together.:)
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got that right i have one in the bay now with a f** up modern dist plate that was acting up int. it backfired so loud in the shop i had to go change my underwear and the poor lady sitting in the waiting room while her car was being fixed almost had a heart attack
 
Mitch//pa said:
got that right i have one in the bay now with a f** up modern dist plate that was acting up int. it backfired so loud in the shop i had to go change my underwear and the poor lady sitting in the waiting room while her car was being fixed almost had a heart attack
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Hahahaha... I wonder who owns that A.
 
well we did a lot of things as all of you suggested one at a time and then test drove it. nothing worked. we replaced distributor carb coil checked for lose wires on popout did not repalce popout checked wires behind dash, poling choke no help, turning the cav no help. Gary Formhals presadent of Whidbey Island A's have worked on it for two days no help but thanks will go at it again tomorrow
 
Back many years ago I had a problem where the car would develop a very rough running condition, and loss of power after being run for about the same amount of time as you suggested in the first post. After going thru a similar list of parts replacements, an older fellow who ran a restoration shop suggested using some Bardahl. Couldn't find any, but did try some STP thru the carb. After three restarts, short drives, and cool-offs, the problem left and never came back. Final diagnosis was multiple stuck valves, once engine reached operating temp. If this is your problem, I would guess the number stuck is likely less than mine !!!
 
A vaccum guage connected to the intake while driving might help find the problem. If the needle starts to flicker at the same time the problem begins, then look for sticking valves. A can of Sea-Foam in the gas and another can in the oil might fix it.
 
Tom Wesenberg said:
A vaccum guage connected to the intake while driving might help find the problem. If the needle starts to flicker at the same time the problem begins, then look for sticking valves. A can of Sea-Foam in the gas and another can in the oil might fix it.
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Just got back from another test by-passed the pop out- did it again! Shorted out the plugs while hot and running of course One and four did nothing, 2 and 3 the engine idles down! Sounds like valves sticking??? Injected mmo in the carb while hot waiting for cool down in the Am We will try the stp in the carb trick. after that pull the valve cover and investigate. Thanks All!!!
 
Lycoming-8 said:
Back many years ago I had a problem where the car would develop a very rough running condition, and loss of power after being run for about the same amount of time as you suggested in the first post. After going thru a similar list of parts replacements, an older fellow who ran a restoration shop suggested using some Bardahl. Couldn't find any, but did try some STP thru the carb. After three restarts, short drives, and cool-offs, the problem left and never came back. Final diagnosis was multiple stuck valves, once engine reached operating temp. If this is your problem, I would guess the number stuck is likely less than mine !!!
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How did you put the stp thru the carb. its thick!!! This is our next test!!! Thanks.
 
As thick as STP is, I can't imagin it getting sucked up the intake and onto the valve stems. Sea-Foam is a good solvent and would be my first choice.

When I first saw STP, I thought maybe he meant LPS, but I guess not. :confused:
 
Ha, Ha, back in the day (early 60's), all of the fancy stuff of today was not available. So, yeah the STP wasn't easy. I made a 'dam' out of card-board that I could pour a little bit of the STP into and then close it up over the choke port. When the engine started to gag, I'd open it up a bit and let it breathe. Then repeat it again and again till I had about 3/4ths of the can into and thru the carb. The remainder went into the crankcase. This was one case where a downdraft carb would have been helpful.
 
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