I bought a 70 340 Barracuda about 3 months ago. The car was originally a 383, 2 barrel. It idles rough and smelled like raw fuel from the exhaust. I went through the carb, Edelbrock 1407, 750cfm. The floats level was way off. I adjusted the floats, the fuel smell is gone. I also adjusted the fuel pressure. My mechanic thinks that may be the engine has a cam, which is causing the thumping idle. The car is an AAR clone. It looks like the previous owner raced the car. Driveshaft loop, upgraded ignition, etc. Is there a way I can check what type of cam I have without taking the cam out? Thanks
Rough Idle
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Challenger RTA
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I always think simple to start. Check plug wires, spark plugs, cap and rotor for corrosion. Worn distributor. Correct voltage to ballast resistor and coil, bad and loose connection. Hot wire it to eliminate the cars wiring. Carburetor dripping fuel inside, choke working, blocked filters, fuel pump good? . Vacuum leak? follow through with compression and leak down test. Don't think Know. Mechanics make money thinking. Make them check and know or do it yourself.
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The car came with an MSD ignition box, coil, and distributor. the plugs and fuel pump, and fuel filter are new. I checked many times, it doesn't look like fuel is dripping into the carb. I'll double check, I don't think the MSD is connected to the ballast resistor. The choke is working and there doesn't seem to be a vacuum leak (sprayed carb cleaner). I need to do a the leak down test. I checked the temp on each cylinder (with a laser thermometer). Number 1 cylinder is a liter cooler than the rest of the cylinders. Also, I tried to tune the carb with a vacuum gauge. The RPM goes up but the vacuum stays at 15. I have the timing at 14 BTDC and total at 30. The engine runs fine above idle. Thanks
Challenger RTA
Well-Known Member
I would swap that wire and then the plug to an other cylinder, see if it follows. Not that this is it. Check to be sure the distributor vac adv is working.
Challenger RTA
Well-Known Member
Maybe I missed that you said you had a steady vacuum reading. I had engines run like that. Burnt, bent, sticking valve or other. Use an vacuum gauge to diagnose. Process of elimination before you tear into it.
Xcudame
Well-Known Member
15" of vacuum is good! Vacuum gauge is the Mopar secret tool for tuning and diagnosing!
I haven't checked the vacuum advance. The vacuum is steady at 15, at idle. I'll also try the wire swap. Thanks
I pulled the plugs after it warmed up. The plugs were black. I checked again to see if gas was leaking into the carb from the primaries and secondaries. No leak. I drove the car and checked the plugs. They were a light tan color. Gas must be leaking from somewhere at idle, I just can't find the source. Thanks
Bret Schneider
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Does the engine oil have a stronger than normal gas smell? Seem like the oil is overfilled?
If that's the case and you're using a mechanical fuel pump there's a chance the fuel pump diaphragm is leaking fuel into the crankcase. Yeah it should leak out the pump weep hole first but that doesn't always happen. Fuel in the oil can cause rough idling since those fumes are pulled into the intake via the PCV and can drive the mixture rich.
If that's the case and you're using a mechanical fuel pump there's a chance the fuel pump diaphragm is leaking fuel into the crankcase. Yeah it should leak out the pump weep hole first but that doesn't always happen. Fuel in the oil can cause rough idling since those fumes are pulled into the intake via the PCV and can drive the mixture rich.
I don't smell any gas in the oil. I just switched from an electric fuel pump to a mechanical pump. I think there's something going on with the carb. Thanks
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