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Hey everybody... I need some serious help! I picked up my '79 Bronco from my Uncle's cabin after he passed away. He had put this freshly rebuilt 460 in it and took it up the mountain. I never saw the truck again until after he passed. So I know nothing of it's running condition for the last 10 years or so other than it sat for at least 9 of the years. All I know is it runs like s*** now and he's gone so I have no more help.
I'll start with symptoms and already replaced parts: Extreme miss-fire, header primary tubes filling up with fuel (cylinders 1,4, and 6), spitting raw fuel and smoke out of the exhaust. I've replaced plugs, wires, distributor, coil, ignition control module, and carburetor. The truck used to only run like s*** for a few minutes until it warmed up (no, it's not a choke issue... choke was removed after it started doing this) then it would run alright. Now, it's getting worse and not clearing up. I've racked my brain and for the life of me can't figure it out. Please help
 

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What kind of fuel pump does it have? Since you've changed carbs, I'm going to GUESS that they are not the issue, although it still could be. If you hadn't changed carbs I would've guessed float or needle issues, but since you did, I'd be looking at the fuel pressure getting to the carb. Too much pressure will push past the float/needle seat and flood the engine. Should be around 7 psi at the carb.
 

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What kind of fuel pump does it have? Since you've changed carbs, I'm going to GUESS that they are not the issue, although it still could be. If you hadn't changed carbs I would've guessed float or needle issues, but since you did, I'd be looking at the fuel pressure getting to the carb. Too much pressure will push past the float/needle seat and flood the engine. Should be around 7 psi at the carb.
Thank's for the reply. Yeah It's got about 6psi at the carb. Checked that before I went out and bought a 600 dollar Holley for it haha
 

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I'm ASSUMING you've done the basics like firing order, setting timing, and such. Time for a compression and leak down check. Definitely don't run it like that, if it's actually got fuel filling up the header tubes there is something seriously wrong there, and your oil has got to be full of raw fuel.
 

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Yes... I've done the basics. No anomalies or major discrepancies that would give an explanation as to why it's running this way. That's why I've spent over a grand on parts and why I'm on a forum asking for help man. Thanks for the obvious advice though. 😆
 

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Sounds like you just threw some parts at it and hoped for the best. Have you done a Compression Check ? Have you checked for a Vaccum Leak around the Manifold? What sizs Carburetor did you put on it.? It must be a special carb for 600.00 dollars. If it has been sitting that long , did you drain the fuel and start fresh? A lot of questions may sound basic and Obvious but we dont know a thing about your skills or the condition of your truck except what you say.
 

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Well, if you read through posts you'd see where I said I did all of that before going out and spending money on parts. And 600 bucks for a new polished Holley 750 double pumper is what summit had it for. So before you armchair mechanic me and assume I've done no trouble shooting maybe you should read into it more and offer some actual advice? Thanks a lot bud
 

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Discussion Starter #8
18in of vacuum, no leaks around the manifold or carb, fresh fuel, new filter, electric fuel pump, compression test was good.
 

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By primary tubes filling up with fuel, what do you mean exactly? Are you temp gunning them and they're colder, or do they literally have fuel going into them, and if so how have you determined that? I know they can't actually fill with fuel as it'd all go out the collector, so what are you saying?
 

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Well... When fuel bubbles out of the gasket between the header and head, and the spark plug comes out soaked in fuel, that would lead me to believe that the primary tube for those cylinders are filling up with fuel. :rolleyes:
 

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Alright lets think about this logically: You've gone through and checked the carb, including changing the carb for a new one with no change. You've also checked fuel pressure, and it's where it's supposed to be. You've got fresh fuel and it's obviously getting there. Let's move on from fuel related. We've got mechanical issues or ignition problems.

You've done a compression test and it checks out. What were the numbers? What about a leakdown test? What were those numbers?

You've checked firing order and timing, but have you checked actual spark at the plugs? And by at the plugs, I mean pulling the plug out of the cylinder head and using the ones that are actually installed in the engine, not ones you've got on the shelf or a "spark tester".

If your compression and leakdown both check out good, and you determine that the plugs are firing nice and strong on ALL 8 cylinders, it's time to get to the mechanical. Pull a valve cover and make sure the valves are all moving like they should and you don't have a flat cam or bent pushrods or the like. Pressure test your cooling system and see if it bleeds off like a blown head gasket. After that, I'd say it's time to really tear into it.
 

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I gotta agree with 72', sounds like stuck valves to me. I agree, pull the covers again and roll over by hand and observe the valves. Best of luck and condolences for your Uncle.
 
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