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Discussion Starter · #1 ·
So I’ve rebuilt this car from the ground up with basic knowledge and currently I’ve got it almost all together but there is one problem I’m a noob with big engine carburetors and I can’t find this out to save the life of me the engine always has a bit of a stumble starting it sounds like it throws a fireball or two down the exhaust before it comes to life and it’s running rich af but I can sit there and turn on the screws all day and it does nothing at all so I hooked a vacuum gauge to it and it reads a perfect 16 at idle the timing is set to 10 advance with 33 total and has a hei style distributor and a Chinese copy of a motor craft 2100 on it which I just replaced the power valve in and i want to take this car to my schools homecoming which is this week I’m probably overlooking something can someone help me please?
 

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1990 Ford Mustang LX 351M powered!! Project Cherry Bomb!!
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How do you have your fuel system set up? IE, fuel pump, regulator ect... Have you double checked the firing order on the distributor? It's good you're using a vacuum gauge! 👍 Have you checked for any leaks? Old vacuum lines, caps, even the vacuum line to the tranny if it's an automatic?
 

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Discussion Starter · #3 ·
How do you have your fuel system set up? IE, fuel pump, regulator ect... Have you double checked the firing order on the distributor? It's good you're using a vacuum gauge! 👍 Have you checked for any leaks? Old vacuum lines, caps, even the vacuum line to the tranny if it's an automatic?
All the emissions stuff was destroyed when I bought the car the thing was destined for the crusher and i pulled it out and fixed it up it had an auto and I put a borg Warner t5 in it and I’ve checked and plugged any leak I think the brake booster has a leak tho it’s got the stock fuel pump and a mr gasket regulator set at 5
 

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A lot of times if you’re turning the idle air screw and it does nothing then you have the throttle blade open too far so you’re off the idle circuit and on the primary circuit. If it was a typically holley you can turn the carb over and see how much transition slot is open. If you set the throttle blades with the correct amount of transfer slot showing and the idle is too low then you have to drill a small hole in each butterfly. This will allow the correct amount of air in while still being on the idle circuit. Then you can properly tune idle with the idle air screws.

Sometimes a big camshaft can cause issues with idle air but if you have a 2100 carb then you surely dont have a giant cam.

Im not sure how to adjust a 2100 carb, never worked with one. According to google they biggest ones arent much bigger than 400cfm. Id throw it in the trash and get used holley 650 if you’re on a budget. I have 2 sitting around the shop…
 

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Discussion Starter · #5 ·
A lot of times if you’re turning the idle air screw and it does nothing then you have the throttle blade open too far so you’re off the idle circuit and on the primary circuit. If it was a typically holley you can turn the carb over and see how much transition slot is open. If you set the throttle blades with the correct amount of transfer slot showing and the idle is too low then you have to drill a small hole in each butterfly. This will allow the correct amount of air in while still being on the idle circuit. Then you can properly tune idle with the idle air screws.

Sometimes a big camshaft can cause issues with idle air but if you have a 2100 carb then you surely dont have a giant cam.

Im not sure how to adjust a 2100 carb, never worked with one. According to google they biggest ones arent much bigger than 400cfm. Id throw it in the trash and get used holley 650 if you’re on a budget. I have 2 sitting around the shop…
Yeah I’d like do do that but I really don’t have any money to work with here I’m just scraping by after building this thing for my senior year of high school and drilling holes wouldnt there just be some type of adjustment and do I drill into the base of the carb or the throttle blades it’s running rich I can tell you that
 

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1990 Ford Mustang LX 351M powered!! Project Cherry Bomb!!
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Simple way to check if the brake booster has a leak, unplug it and block off that source, check your vacuum gauge again and see if there's a change... You said it's got a stock fuel system... Does that mean the electric pump in the tank?? If so are you sure you've got the fuel psi down to 5? Is that with a return style setup? Reason I'm asking I just went thru the same mess getting the fuel psi down on mine even tho I put a new electric pump in it with a lower psi rating. If you've got too much pressure going to the carb it'll blow the needle off the seat and flood the car out all the time.. Pull a plug or 2 and see if they reek of gas..
 

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Discussion Starter · #7 ·
Simple way to check if the brake booster has a leak, unplug it and block off that source, check your vacuum gauge again and see if there's a change... You said it's got a stock fuel system... Does that mean the electric pump in the tank?? If so are you sure you've got the fuel psi down to 5? Is that with a return style setup? Reason I'm asking I just went thru the same mess getting the fuel psi down on mine even tho I put a new electric pump in it with a lower psi rating. If you've got too much pressure going to the carb it'll blow the needle off the seat and flood the car out all the time.. Pull a plug or 2 and see if they reek of gas..
My plugs! Omg i forgot that they can foul now I feel dumb af but anyways I think those are fouled now that I think about it because all the starting and that one test drive I did with it out of time badly that might’ve fouled my plugs and be the reason and I’ll probably just toss the one from my parts car which is brand new on the parts car if it does show fault
 

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Discussion Starter · #8 ·
My plugs! Omg i forgot that they can foul now I feel dumb af but anyways I think those are fouled now that I think about it because all the starting and that one test drive I did with it out of time badly that might’ve fouled my plugs and be the reason and I’ll probably just toss the one from my parts car which is brand new on the parts car if it does show fault
Oh and also the fuel system is running that low because if I turn it lower it acts like it’s running out of fuel completely after a few minutes of running and revving and it’s the stock in tank setup for my pump and it comes back up and goes to the regulator and then there’s no return line but it’s not pushing past it I’ve checked that already
 

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Discussion Starter · #9 ·
Oh and also the fuel system is running that low because if I turn it lower it acts like it’s running out of fuel completely after a few minutes of running and revving and it’s the stock in tank setup for my pump and it comes back up and goes to the regulator and then there’s no return line but it’s not pushing past it I’ve checked that already
So I’ve pulled my plugs out and they are all completely drenched in oil soooo I’m not sure if I have bad valve seals or if my intake manifold has a crack in the bottom or if something else is junk because I doubt all my rings and Cylender walls are junk
 
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