help with Carb?
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New User
Joined: Aug 2004
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help with Carb?
hi all im new to this site and fords and i need help. I have a 68 early bronco with a 95 ford 5.0(302) that was pulled from a truck. i got it for free and a had no funds for a rebuild. i took off all the efi and have a holley intake 650 carb headers MSD 6 with rev limiter and dist mechanical advance only. all accesories are brand new. i have a brand new trans with a 1600 stall on it. my problem? it is idling great all timing is good and the advance is good but at about 1000-2000 rpms it starts to die it has a deeper sound and sounds like maybe no gas? we have adjusted the floats and out side adjustment from very lean to too rich no change. the fuel pump is a holley red and a regulator set at 7 and the pressure is 7. when we first hooked it all up it was back fireing because we had the firing order wrong. it has the 351 order. it is all correct know just boggs at 1000 or so
please help
please help
Elder User
Joined: Jul 2001
Posts: 602
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From: Huntersville
First, welcome aboard.
How old is the carb? Known good carb? With a timing light make sure you're getting some mechanical advance as the engine rpm's increase.
Sounds kind of like it's running out of gas to me. Are there any inline filters that might be full? Could the sock in the tank be plugged? Had the Bronco sat along time before you put the new engine in?
Any chance the rpm limit pill in the msd box is too low? Can they even go that low? lol
keep us informed on how it goes and what you try and we'll try to help. Start on the cheaper things first. Don't run out and buy a new ignition box or distributor until you proove the old ones are bad. It's too easy to throw money at a problem, waiste alot of money and still not fix it.
Test the distributor, what kind is it?
make sure all your battery cables are good and clean. make sure they are not corroded up inside of the jacket. They can cause alot of wierd problems.
Make sure you have a good engine ground also.
Good luck
Clint
How old is the carb? Known good carb? With a timing light make sure you're getting some mechanical advance as the engine rpm's increase.
Sounds kind of like it's running out of gas to me. Are there any inline filters that might be full? Could the sock in the tank be plugged? Had the Bronco sat along time before you put the new engine in?
Any chance the rpm limit pill in the msd box is too low? Can they even go that low? lol
keep us informed on how it goes and what you try and we'll try to help. Start on the cheaper things first. Don't run out and buy a new ignition box or distributor until you proove the old ones are bad. It's too easy to throw money at a problem, waiste alot of money and still not fix it.
Test the distributor, what kind is it?
make sure all your battery cables are good and clean. make sure they are not corroded up inside of the jacket. They can cause alot of wierd problems.
Make sure you have a good engine ground also.
Good luck
Clint
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New User
Joined: Aug 2004
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thanks all
the tank is brand new the filter is brand new the carb holley 650 is frond new the dist msd bullet is brand new it is getting advance. the carb is very dirty from the back firing so im going to try and clean it today after work. also the revlimiter is set at 6000. but i also disconnected it with no luck all gronds are tight and all cables and all the wireing in the truck is new. all the fuel line is also new. it is a mixture of hard line and braided stainless. thanks for your really fast reply
Elder User
Joined: Jul 2001
Posts: 602
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From: Huntersville
Is the Holley new enough to have the power valve blow out protection? even then it's possible the power valve could be blown but then it would be real rich at idle also.
How does it idle? nice and smooth then just cuts out and backfires when you try to rev it up? have you checked the dist. to make sure it has the springs in it? Just guessing here trying to give you some ideas.
Is the carb a vacuum secondary or mechanical? Could the secondaries be flopping open flooding it. When the engine is idleing take a mirror and look into the throttle ventura carfully, have a friend bring the rpm's up until it is just before acting up if possible, see if it's getting a rush of raw, liquid gas down the carb from the boosters or any where else.
Clint
How does it idle? nice and smooth then just cuts out and backfires when you try to rev it up? have you checked the dist. to make sure it has the springs in it? Just guessing here trying to give you some ideas.
Is the carb a vacuum secondary or mechanical? Could the secondaries be flopping open flooding it. When the engine is idleing take a mirror and look into the throttle ventura carfully, have a friend bring the rpm's up until it is just before acting up if possible, see if it's getting a rush of raw, liquid gas down the carb from the boosters or any where else.
Clint
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New User
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it idles real good and it revs to any rpm real smooth no shimmy no loud noises or ticks pings or knocks, thoughout the rpm range. it is just when it is under any load. the carb is new enough but i will check it for blow out. the distributor is all working very well with the correct springs. i have gone up and down on the advance curve with no change to the symptoms. could it have any thing to to with my low stall converter 1600 thanks for the help.
Posting Guru
Joined: Jul 2001
Posts: 2,119
Likes: 2
From: Southern New Hampshire
Hook up a vacuum gauge and see if there are any strange readings, fluctuations, etc. Check all possibilities for any vacuum leaks; use a spray bottle with water. Retorque the carb base.
Ive heard several rumbles about Holleys being bad out of the box. If possible borrow another one.
Ive heard several rumbles about Holleys being bad out of the box. If possible borrow another one.
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New User
Joined: Aug 2004
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any idea what the vacum should be?
also, is it the accelerator pump that is on the front of the carb on the drivers side with a spring on it? What ever it is, when that activates it flows out raw fuel is that right?
Thanks all
also, is it the accelerator pump that is on the front of the carb on the drivers side with a spring on it? What ever it is, when that activates it flows out raw fuel is that right?
Thanks all
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Lead Driver
Joined: Feb 2003
Posts: 8,140
Likes: 4
From: Oak Harbor, OH
That is the accelerator pump, it squirts raw gas into the system. Is the choke working? If not then it can cause those symptoms. Let the truck run and get warmed up some before tryin to drive it. A healthy engine should have between 17 and 20 in/hg vacuum.
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New User
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just a note the choke is macanical. i let it dit and warm up to a 190 running temp and then tried to drive it didnt work? when i use the choke on cold mornings is knocks really bad untill i gie it some gas then idles great
thanks again for the help i really need it and please keep it coming
thanks again for the help i really need it and please keep it coming
New User
Joined: Jul 2001
Posts: 22
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Check power valve
I had similar symptons on a Holley, newly rebuilt unit. I changed the power valve (and dropped from a 8.5 to a 6.5 unit) and the carb ran great after that. I think i blew the power valve on my motor start up and it actually got worse the more I tried to drive it.
New User
Joined: Jul 2001
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Its very easy. First Autozone sells them for about $4 or $5. I got mine at Jegs for around $6.99. Take the front fuel bowl off. 4 screws. Try to pull it off without destroying your gaskets. With some luck, the gaskets will be good otherwise, they will have to be replaced. But the power valve will be screwed into the side. Remove it, put new one in and replace fuel bowl. I took carb off motor to do it adn it took all of 10 minutes. Gaskets were all good. Put some vaseline on gaskets, this will help to keep them intact on any future carb removing. 
thanks every one