1966 Ford 4000 backfire

JDavidm · Jul 9, 2015

My 4000 3 cylinder backfires when I back down the throttle, it will run like a top all day, but when you let off of it, it pop like a gun. Will do it with the stock exhaust pipe or a straight pipe.
Messed with timing a bit, no change, changed plugs and looked for any leaks in the intake and exhaust manifolds. What should I look for next ?
Thanks in advance.

David

cole in mo. · Jul 9, 2015

Carb may be a little rich, and cutting the throttle quickly, might send unburnt gas into the manifold, and it fires off there.

old · Jul 9, 2015

Not uncommon to happen and if you have been running it for an hour or more normal due to being warm and when you back it off it does spin down it sucks more gas in so it hits hot spots and back fires due to that. You may also have carbon build up which can cause it.

1966 Ford 4000 backfire

JDavidm

Member

cole in mo.

Well-known Member

old

Well-known Member

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