My 460 is backfiring a lot.
Thread Starter
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Mountain Pass
Joined: Jan 2019
Posts: 183
Likes: 19
From: Columbus Ohio
My 460 is backfiring a lot.
Link to the Bullnose forum page for this ongoing issue.
https://www.ford-trucks.com/forums/1753762-my-460-backfires-a-lot.html#post21223565
Any ideas fellas?
Everything is as it should be, and I will fix my exhaust leaks ASAP.
I feel like I'm running too rich, but no one seems alarmed by the 19in/hg of Vacuum at the Carb.
Bullnose forum thread
https://www.ford-trucks.com/forums/1753762-my-460-backfires-a-lot.html#post21223565
Any ideas fellas?
Everything is as it should be, and I will fix my exhaust leaks ASAP.
I feel like I'm running too rich, but no one seems alarmed by the 19in/hg of Vacuum at the Carb.
Bullnose forum thread
Tuned
Joined: Nov 2022
Posts: 267
Likes: 28
From: Coon Rapids
check the plugs wires to make one is not leaking voltage to another one .with that vacuum your valves should be sealing .dose it back fire at idle ,or under load ? if it is a holley you probably need to change the power valve ,they get wreaked from back fires .what is your timing set at ? are your plug wire in the correct firing order ?
Hotshot
Joined: Jul 2020
Posts: 10,268
Likes: 2,563
From: Near Salt Lake City
Raw fuel in the exhaust?
Rich condition from the Holley?
Thermactor sending downstream air when it should be farting to atmosphere?
Do some checks on the diverter valve and the TAB and TAD solenoids
Check the float level
Replace the power valve (above info correct about backfires taking out the power valves on carbs)
Have an IM test done on manual mode, get a printout to see just how rich it is running
Rich condition from the Holley?
Thermactor sending downstream air when it should be farting to atmosphere?
Do some checks on the diverter valve and the TAB and TAD solenoids
Check the float level
Replace the power valve (above info correct about backfires taking out the power valves on carbs)
Have an IM test done on manual mode, get a printout to see just how rich it is running
Cargo Master
Joined: Oct 2020
Posts: 2,631
Likes: 761
With a carburetor any time you are running along at high engine speed and then close the throttle the manifold vacuum will spike higher and this causes extra fuel to be pulled from the idle circuit. A lot of this passes through the engine and if there is a source of air and a high temperature surface it can ignite and make a bang, blow up the muffler etc. You probably are running on the rich side and you have some air leaks especially up near the engine and that's what is causing the problem. On the carburetor you might want to try cutting back at the idle restrictions by taking off the block and hooking a wire into the orifice. Most of the time I just use a piece of wire from some stranded copper wire. Most of the time the individual strands are about .013 thick. Just hook it through the idle feed restriction on both sides of the primary metering block, put it back together and readjust your idle mixture. What this will do is lean the idle and transition circuits of the carburetor. See if it will tolerate this change without surging at part throttle. If it will you'll also get better mileage.
Thread Starter
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Mountain Pass
Joined: Jan 2019
Posts: 183
Likes: 19
From: Columbus Ohio
check the plugs wires to make one is not leaking voltage to another one .with that vacuum your valves should be sealing .dose it back fire at idle ,or under load ? if it is a holley you probably need to change the power valve ,they get wreaked from back fires .what is your timing set at ? are your plug wire in the correct firing order ?
I bought 11mm thick wires and then used split loom to make sure there is no arcing/shorting. I also watched for spark after dark. All good.
It doesn't backfire at idle. Only when coasting/decelerating in gear. Does not backfire in neutral.
I will order a new Power valve. It backfired through the carb a couple of times when I was tuning last year.
Firing order has been triple checked.
Moderator
Joined: Aug 2002
Posts: 6,094
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From: Southern California
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Lead Driver
Joined: Mar 2004
Posts: 8,922
Likes: 152
Plugs and wires are new since posting here.
I bought 11mm thick wires and then used split loom to make sure there is no arcing/shorting. I also watched for spark after dark. All good.
It doesn't backfire at idle. Only when coasting/decelerating in gear. Does not backfire in neutral.
I will order a new Power valve. It backfired through the carb a couple of times when I was tuning last year.
Firing order has been triple checked.
I bought 11mm thick wires and then used split loom to make sure there is no arcing/shorting. I also watched for spark after dark. All good.
It doesn't backfire at idle. Only when coasting/decelerating in gear. Does not backfire in neutral.
I will order a new Power valve. It backfired through the carb a couple of times when I was tuning last year.
Firing order has been triple checked.
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