390 keeps flooding need help
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Fleet Mechanic
Joined: Jun 2007
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From: Ohio
390 keeps flooding need help
I posted this in the FE section too but so far no response. so here it is:
I have a 4bbl intake on my 390, and an edelbrock 750/w manual choke on it. #1407. I can drive this truck just fine for the most part, it has good power while using the primary two barrels. (I think the ones always in use are the primaries?)
Anyways if i open all four up, pedal to the floor, but at about 45+ mph, the engine runs no problem, although it seems to drop rpm slightly once the 2nd two barrels are opened.
BUT, if I am shifting, like today example 2nd to 3rd, and floor it from the shift, it popped and died out, flooded. Happened to me twice today within an hour. the first time it flooded i'm not sure why it happened, but the second time was as stated above. Is the carb just too much and floods when floored like that? Anything I can do to help eliminate this? accelerator pump setting? If I have too i'll end up buying a 600 eventually, but stick with the 750 for now...
I have a 4bbl intake on my 390, and an edelbrock 750/w manual choke on it. #1407. I can drive this truck just fine for the most part, it has good power while using the primary two barrels. (I think the ones always in use are the primaries?)
Anyways if i open all four up, pedal to the floor, but at about 45+ mph, the engine runs no problem, although it seems to drop rpm slightly once the 2nd two barrels are opened.
BUT, if I am shifting, like today example 2nd to 3rd, and floor it from the shift, it popped and died out, flooded. Happened to me twice today within an hour. the first time it flooded i'm not sure why it happened, but the second time was as stated above. Is the carb just too much and floods when floored like that? Anything I can do to help eliminate this? accelerator pump setting? If I have too i'll end up buying a 600 eventually, but stick with the 750 for now...
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Joined: Dec 2001
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From: Louisville,Ky.
It doesn't have secondary floats. It just has one on either side.
1st, I would get a gauge and check your fuel pressure. It should be between 4-6psi. It almost sounds like they are too low and under a load it is starving for fuel.
1st, I would get a gauge and check your fuel pressure. It should be between 4-6psi. It almost sounds like they are too low and under a load it is starving for fuel.
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Fleet Mechanic
Joined: Jun 2007
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From: Ohio
no i think the pressure should be fine, as the filter towards the carb is full pretty much all of the time. every now and then there is an air bubble towards the top but goes away once the truck it driven.
New User
Joined: Mar 2011
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NW 150, Does that engine have vacuum advance on distributor if so you might want to check for vacuum leaks, could be engine is taking away from that when ya stomp on and also does it have vacuum secondaries. Since vacuum controls timing on older models. just a thought, It don" cost nottin to try
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Joined: Dec 2001
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From: Louisville,Ky.
The Edelbrock carbs use a non adjustable air flap uover top of the butterflies on the rear. This opens slowly to eliminate bog when the mechanical lower blades open.
Which hole on the accelerator pump arm is the rod in? Try the one closest to the carb first and work your way out (there are 3 holes) and see if this helps the bog when opening up the rear barrels.
Also, make sure your vacuum advance is hooked to the front port with no vacuum at idle (left one) and the initial timing is at around 10* btdc.
Which hole on the accelerator pump arm is the rod in? Try the one closest to the carb first and work your way out (there are 3 holes) and see if this helps the bog when opening up the rear barrels.
Also, make sure your vacuum advance is hooked to the front port with no vacuum at idle (left one) and the initial timing is at around 10* btdc.
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Thread Starter
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Fleet Mechanic
Joined: Jun 2007
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From: Ohio
Yea i changed the setting on the accelerator pump to the top hole or i guess it'd be the one closer to the carb. That would give it a smaller amount of gas right?
I'm too lazy to look at what i have posted on this so far but what actually happened was the distributor gear pin sheared. not sure why but it did so i bought a new pin and put it back together and set it right on 10 BTDC. So that's good to know i put it where it should be. I want it to be timed where it will run the best, not factory.
The dizzy is the motocraft one it's blue and has the cone in the front for the line to run to the carb, which is hooked up to the left port on the front of the carb like you said.
I haven't had a chance to just gun it really yet because I'm paranoid now that the pin will shear again.
I'm too lazy to look at what i have posted on this so far but what actually happened was the distributor gear pin sheared. not sure why but it did so i bought a new pin and put it back together and set it right on 10 BTDC. So that's good to know i put it where it should be. I want it to be timed where it will run the best, not factory.
The dizzy is the motocraft one it's blue and has the cone in the front for the line to run to the carb, which is hooked up to the left port on the front of the carb like you said.
I haven't had a chance to just gun it really yet because I'm paranoid now that the pin will shear again.
Moderator
Joined: Dec 2001
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From: Louisville,Ky.
It shouldn't. Probably just an old weak pin. You get the same amount of fuel in the different holes, it really controls how fast you get it. The inner hole is fastest and the outer is slowest.
Get her good and warmed up and give her a romp and see how she does!!
Get her good and warmed up and give her a romp and see how she does!!
Thread Starter
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Fleet Mechanic
Joined: Jun 2007
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From: Ohio
Alright well this isn't my carb but it's pretty much no different. which setting are you talking about to make sure i have mine right?
And i'll give it some throttle the next time i drive it
It flooded a little again on me yesterday when i tried to start it after letting it sit for about 10 minutes after drivings it at temp. But then i held the pedal to the floor and it caught it's breath and started.
I'm really contemplating taking it to a shop in my area that works on carbs and see what they can do. hope it wouldn't cost too much though.
And i'll give it some throttle the next time i drive it
It flooded a little again on me yesterday when i tried to start it after letting it sit for about 10 minutes after drivings it at temp. But then i held the pedal to the floor and it caught it's breath and started.
I'm really contemplating taking it to a shop in my area that works on carbs and see what they can do. hope it wouldn't cost too much though.
Moderator
Joined: Dec 2001
Posts: 22,436
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From: Louisville,Ky.
That is heat soak. A totally different problem. For that, I highly recommend a heat shield between the carb and intake.
That is the adjustment I was speaking of. If it tried to bog when you floor it, try the other holes and see if it gets better or worse.
That is the adjustment I was speaking of. If it tried to bog when you floor it, try the other holes and see if it gets better or worse.
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Fleet Mechanic
Joined: Jun 2007
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From: Ohio
And tomorrow I think I'll call up that local shop i mentioned and see what they can do to my carb setting wise to lower the cfm it's putting out or whatever can be done to it. Obviously i'm still not knowledgeable about these old things yet
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Fleet Mechanic
Joined: Jun 2007
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From: Ohio
Also i haven't mentioned, the truck can be a dog off the line from time to time. Now i don't gun it but I usually have to give it a generous amount of throttle at take off or the engine will fall on it's face and loose all of it's power. It runs, but it just chugs until it gets back up to about 1300-1500 rpm and gains all power back. I've read that too big of carb will cause this?
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Also i haven't mentioned, the truck can be a dog off the line from time to time. Now i don't gun it but I usually have to give it a generous amount of throttle at take off or the engine will fall on it's face and loose all of it's power. It runs, but it just chugs until it gets back up to about 1300-1500 rpm and gains all power back. I've read that too big of carb will cause this?
Try giving it some choke( u said it's manual)when it falls on it's face.
Try giving it some choke( u said it's manual)when it falls on it's face.