460 big block help
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Freshman User
Joined: Aug 2011
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From: molalla
460 big block help
I got a 460 that won't stay Runing and if I hold my foot just right she will run sounds bad and if I put her in gear she won't move and won't even try to. I've check the cap and rotor and the plugs and wires all is good and its shooting gas and fuel thu the carb. What is doing this? And what can I so to fix it?
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Freshman User
Joined: Aug 2011
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From: molalla
The truck is a 1986 f350 but the motor is a late 70s 460 and is a automatic 4x4 and just a small amount of throttle to much and it dies or shoots gas and flames out of the carb
It run good intill one night she started to run out of fuel and then this started..... this is not the first time it has run out of gas.
It run good intill one night she started to run out of fuel and then this started..... this is not the first time it has run out of gas.
Laughing Gas
Joined: Oct 2010
Posts: 997
Likes: 2
From: Rock Valley, IA
Sounds to me like there is a flooding/timing issue. Was the carburetor ever left sitting dry and, if so, for how long? The flame shooting out the carb sounds like your intake valve is open when it's firing.
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From: molalla
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Laughing Gas
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Laughing Gas
Joined: Oct 2010
Posts: 997
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From: Rock Valley, IA
You'll need to get a timing light (or get one from someone that has one) and check your timing on the balancer. There should be a tab and degree markings. You'll put the induction clamp on No. 1 spark plug wire and ground to the battery. Start the truck (you'll need someone to help with this to keep it running in your situation) and point the light toward the balancer. You should see the degree marks in the strobe. The mark the tab is above is your degree of advance or retardation. usually you'll look for somewhere between 6-10 degrees BTDC (Before Top Dead Center). Also, remember the engines rotate counter clockwise so BTDC will be to the right of the tab. I'm not sure if I explained this well enough. I'm sure someone will help me out.
Fleet Mechanic
Joined: Jul 2011
Posts: 1,916
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This sounds definitely like a timing issue.
Backfiring through the carburetor can be caused by a burnt up intake valve, ignition timing advanced too much, and sticking/stuck open valves.
How To Guide: Adjusting Ignition Timing - YouTube
Backfiring through the carburetor can be caused by a burnt up intake valve, ignition timing advanced too much, and sticking/stuck open valves.
How To Guide: Adjusting Ignition Timing - YouTube
Moderator
Joined: Jan 2001
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From: Virginia
Back-firing back up through the carb can simply be caused by a lean condition, caused by either not enough fuel or a cold engine that doesn't have a working choke. I suspect carb problems, letting it run out of gas has probably stirred up a bunch of dirt and it has gotten in the carb.
Laughing Gas
Joined: Oct 2010
Posts: 997
Likes: 2
From: Rock Valley, IA
Yes. Timing chain could have something to do with it. Too much slack in the chain could throw the timing off. Take the timing cover off and check the chain. I kind of doubt that's the issue but it couldnt hurt to check. I think Franklin has the right of it. I built the carb on my 460 twice before it would run correctly. I'm guessing you still have the stock carb on. It can be quite the pain to rebuild but it is quite possible. From what you're describing it could be any number of things from timing to bad valves to a fouled carb. It'll take some troubleshooting to get to the root of the matter. Welcome to being a mechanic. 
Moderator
Joined: Nov 2007
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From: Denver Metro Area, CO
You can do a leak-down test to see if the valves are causing problems or not.
How to do Cylinder Leak Down Testing- Car Craft Magazine
How to do Cylinder Leak Down Testing- Car Craft Magazine