I'm having a problem on my 2bbl to 4bbl swap and could use an outside opinion before I go buy a completely NEW carburetor. The car is a 73 Dart with a rebuilt 318. It ran decently with the 2bbl but as it already has headers and a mild cam, I figured the 4bbl would really help it.
The carburetor is a used Holley 4160 I picked up from a member here. I bought a book and a Holley renew kit, tore it all down and put it back together with the new parts
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I thought I did okay, but it's obviously not right.
Initially I had the floats set wrong and flooded the engine. I got that taken care of but then the best I could do was get it to run on less than 8 cylinders. Some of the pipes on the headers weren't getting hot, and I verified by removing a couple plug wires while it barely idled. I had the plugs out multiple times to try and dry out the cylinders, but it never improved.
For a sanity check I decided to put the 2bbl back on using an adapter. I also changed the oil because it was heavily diluted. I was also thinking there could be an issue with fuel pressure, so I put a gauge on to verify that. With the 2bbl back on it ran perfectly and was holding a steady pressure of just over 5.5 pounds.
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To double check the float the levels, I put the Holley on the stand and connected an electric fuel pump and ran that for about a minute. I took out the sight plugs and fine tuned the needle/seat as per the manual. I also verified the bottom of the carb stayed dry. The electric pump only made about 3.5 pounds of pressure though.
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Since everything seemed okay I put the 4bbl back on, but now it wouldn't even start. It fired about about a second then died and just cranked after that. I opened the throttle slightly and saw a plume of gas shoot up from the primary vent tube.
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I'm pretty much at my wits end with this thing. Does anyone have any ideas before I throw it in the scrap metal bin?