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EFI to CARB conversion problem, running like a PIG..vacuum problem?

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5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

EFI to CARB conversion problem, running like a PIG..vacuum problem?

Old 08-27-2015, 05:06 PM
  #1  
YoungStangsMan
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Default EFI to CARB conversion problem, running like a PIG..vacuum problem?

Just got my 1990 GT 5.0 Vert back from my new engine swap it's a Proformance 347 stroker (stock block). Chose to go with a carb this time around since i'm sick of dyno tuning price. Let me first start off by saying the "mechanic" I took my car to isn't quite at the top of his class and made a few mistakes and i'm now left with the option of figuring it out myself or taking it to another person and paying them...


Anyway, when I got the car back for the first time it was missing terribly, the whole car was shaking really bad and I took it right back to him. Few days later got it back and it was running much better but seems like it has no power now. When I asked what was wrong he said the timing was off.


It's an Edelbrock 1406 Carb with a Victor Jr. intake. Seems like the secondaries (vacuum assist) aren't opening but I don't really know how to test that properly to be sure. What I do know is the car doesn't get up and go when you floor it like a healthy mustang should!


Current vacuum hookups: PCV out on Carb is hooked straight up to the "S" port on the Vacuum tree...not the PCV valve in the valve cover...Valve in cover just has a filter on it and is not connected to tree. Is this maybe the issue? The other 2 smaller Vacuum ports on front of the Carb are capped.


Again this is a EFI to CARB conversion on a 1990 GT, using the stock fuel pump going through a regulator with gauge from Summit. Reads about 3PSI while idling. I also notice it idles high even after adjusting timing.


I really appreciate ANY info from yall the tech at Edelbrock wasn't very nice or helpful contrary to what everyone else says... He did however tell me to check and make sure the electric choke blade isn't locked straight up and down.


Diagram of Carb hookups: http://www.google.com/url?sa=i&rct=j...40537537352569




Will post pics of anything requested!!!
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Old 08-28-2015, 07:41 AM
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88 orangepeel notch
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Bump your fuel pressure up to 6 - 7 lbs of pressure to start.

How mechanical are you ? Can you verify timing ? And I'm not being disrespectful, just trying to find out how to help you in the best way.
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Old 08-28-2015, 08:33 AM
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dawson1112
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Ya that carb needs about 6psi of pressure at idle. First thing I thought of when I read the title of efi to carb was if you used stock pump and if so what was the pressure.
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Old 08-28-2015, 08:38 AM
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When you raise the pressure at idle up, youll probly have to adjust the idle mixture screws on the carb so it doesn't idle rich.
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Old 08-28-2015, 04:41 PM
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YoungStangsMan
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Thanks for all the responses guys, this forum is so helpful!


This is the regulator I bought: Holley 12-803
LINK:https://www.holley.com/products/fuel...s/parts/12-803


I'm sure I could figure out how to adjust the output via research but if there's any tips, they'd be appreciated!


I noticed another thing: My fuel line going to the carb is dry-rotted and leaking gas... -Will be replacing that this weekend for sure! Maybe my pressure will come up a little too...When I un-do the fuel rail/gas line to the carb is fuel going to shoot out everywhere?


I am somewhat good mechanically, with the right instructions from someone who knows what they're doing I do pretty well! As far as timing lights, I think I can borrow one from someone, the only thing is when my engine was painted, the harmonic balancer was sprayed too and I didn't see any markings on it. My cousin was over who works at a shop and set the timing for me by ear and got the idle down some but i'm maybe this will have to be re-tweaked after the pressure is raised.


I also noticed besides all of the above, my engine seems like it's overheating, I have a 180 thermostat in (brand new) and I did burp the air out with the rad cap off for like 20 min or so. The thermostat broke at 180 and it just kept slowly climbing up to like 200-210 and I shut it off. Is this too hot? I don't know if i'm just being a worry wart or not I bought an aftermarket gauge cluster from autozone and I plugged the sender into the front of the Victor Jr. Intake. Running dual flex electric fans & 2 row aluminum rad which was purchased last winter.


Again thanks for all of the help guys this is great!
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Old 08-28-2015, 06:24 PM
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dawson1112
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You must time it with a light. You may have to get some paint remover and clean the balancer off so you can find the correct marks and paint them white.
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Old 08-28-2015, 06:41 PM
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YoungStangsMan
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Okay thanks I'll grab one tomorrow and get to work on checking that. Should I also connect the PCV valve from valve cover to the CARB's PCV inlet, or just leave it with the filter on?
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Old 08-28-2015, 07:25 PM
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You mean you have a oil breather on the valve cover? You should still have the pcv valve hooked up.
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Old 08-28-2015, 08:26 PM
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YoungStangsMan
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Correct the PCV valve in the valve cover isn't hooked up to anything, just has a filter on it. I'll plug it into the middle nipple on the carb and see what happens.

Does the pcv need to connect to the Vacuum tree as well? If so I can probably find an adapter.

Thanks
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Old 08-28-2015, 08:33 PM
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Pvc should connect to metered vacuum. Meaning above the throttle blades. So that low vacuum at idle and as throttle increases vacuum increases on pcv. DISREGAURD


Wait you know, I may be wrong about that..^^ let me do some research its been awhile since I messed with a carbd setup

Last edited by dawson1112; 08-28-2015 at 08:39 PM.
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