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Discussion Starter · #1 ·
So i have a sbc that came with the car and really do not have any clue as to it’s history. It ran fairly well when I got it running in the car, the previous owner had never had it running. Previous owner had just installed An HEI. Long story short the hei gear ate the cam gear so I pulled it mostly apart, cleaned it as thoroughly as I could, put a new flat tappet in it new lifters etc and wanted to see how it ran. Covered everything in assembly lube, using zinc break in oil and got the matching gears for cam and distributor
It fires right up and sounds like it runs very good, but it smokes a bunch, black smoke and quite a bit of it. It seems to get worse the longer it runs.
Pulled plugs and each one of them was very black. Definitely unusual. I ran a compression check cold and each cylinder was consistent at about 130.
Wouks love some thoughts about causes of black smoke and really black plugs. Smoke is not blue as I normally would associate with oil.
Appreciate suggestions or thoughts.
 

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Black smoke is typically a fuel-related issue. Running an edelbrock carb, 5.5-6psi max inlet fuel pressure. Holley, around 7 max. Most mech fuel pumps push 9-18+ psi. Not saying that's what it is but you definitely have a fuel problem. Stuck float, jetted way too fat, torn power valve, too much line inlet pressure, timing too retarded, dirty air filter, sooo many things. Even wrong plugs and bad wires...
 

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Discussion Starter · #3 ·
It has a new Holley street avenger on it and that was where I was going to look next. The plugs did come out pretty wet looking so definitely could be the issue.
 

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I concur with Andy, it's most likely a fuel problem. It would be wise to put a fuel pressure regulator and gauge on between the pump and carb. I learned a very lesson about that a few years ago. A regulator and gauge would have saved me a LOT of grief. With those parts in the system you have protection from over-pressure and a tool for diagnosis. Then, tuning the carburetor should be easier because you will know that your fuel pressure is no longer a variable to guess about.
 

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Wet plugs are no good. Are you running points ignition or electronic? There's a resistor wire in stock harnesses for points ignitions that will not give the full 12vdc at the dist you need for solid ignition. If you converted, you will need to get your ignition sorted out with a full 12vdc at the BAT terminal if HEI, if aftermarket, at the power lead to the box. I would start by ensuring your ignition is dialed and base timing is set correctly so you can scientifically narrow down the issue to fuel. May be more than just one thing or may be ignition posing as a fuel system issue too. Gotta be a scientist and a detective :cool:
 

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I would also check fuel pressure going into the carb -- like said in an earlier post should not be greater than 7 psi if it is higher use a fuel pressure regulator. I have an electric and mechanical fuel pump due to extreme vapor lock with my SBC. I was getting like 15 PSI at the carb and had to use a pressure regulator. Also, like many said is distributor cap and ignition wires new? You may also try going to hotter good spark plugs.
 

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Very first thing to do is verify the HEI conversion is running off a full 12v+, the stock wiring harness has a resister wire/ballast resister to lower the voltage to between 7-9 volts to improve the lifespan of the original contact points in the ignition distributor.
HEI will run stinky and black if voltage is too low.

Then look at fuel pressure and carb adjustment.
 

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If it smokes black, your carb is flooding. See if you can borrow a replacement from a friend, type and jetting doesn’t matter for testing purposes. Still floods, try a cheap STOCK mechanical fuel pump from ORileys or Autozone. One of the 2 will temporarily fix it, then when you pickup more junk out of your gas tank and it starts again, you will be ready.
 
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