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9N,2N,8N, Ford Tractors / Re: 9N/2N Backfires
« on: November 06, 2009, 06:41:12 PM »
Burt --
Leave the points at 0.018" -- that's an excellent recommendation; it compensates for wear in the distributor. Basically, you want the points as wide as you can get them and still have spark. The narrower the gap, the weaker the spark.
Backfiring under load is almost always a symptom of weak spark. You say you backfire when closing the throttle, though. I've never seen an N do that although it is very common in large truck engines, etc. due to unburned fuel igniting in the muffler -- these little 120 cid flat heads just don't push that much fuel into the muffler and the muffler isn't that hot (at least not that I've seen.)
I wonder if you don't have weak spark still and it's just showing funny. Have you tried to run a heavy load for a prolonged period (brush hog works, but anything to heat everything up and really work her?) Is the spark at a test plug nice and blue?
If it were me, I'd tune the carb, then pull the carb. drain plug to be sure that gasoline flowed freely, then take the dist. back off and go over everything closely to be sure it's all 100 % and nothing was missed, dirty, etc.
There is a possiblity the valve timing is off, but I doubt it -- it should backfire all the time then.
Hope this helps,
Pete P.
Harborcreek, penna.
Leave the points at 0.018" -- that's an excellent recommendation; it compensates for wear in the distributor. Basically, you want the points as wide as you can get them and still have spark. The narrower the gap, the weaker the spark.
Backfiring under load is almost always a symptom of weak spark. You say you backfire when closing the throttle, though. I've never seen an N do that although it is very common in large truck engines, etc. due to unburned fuel igniting in the muffler -- these little 120 cid flat heads just don't push that much fuel into the muffler and the muffler isn't that hot (at least not that I've seen.)
I wonder if you don't have weak spark still and it's just showing funny. Have you tried to run a heavy load for a prolonged period (brush hog works, but anything to heat everything up and really work her?) Is the spark at a test plug nice and blue?
If it were me, I'd tune the carb, then pull the carb. drain plug to be sure that gasoline flowed freely, then take the dist. back off and go over everything closely to be sure it's all 100 % and nothing was missed, dirty, etc.
There is a possiblity the valve timing is off, but I doubt it -- it should backfire all the time then.
Hope this helps,
Pete P.
Harborcreek, penna.