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Old 07-30-2004, 12:21 AM
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340 mopar motor questions

I've built up a 340 motor with 10:5:1 compression, bored .30" over, the cam I chose was a mopar purple shaft which has a .474" lift with a 280 duration. I am also using a stock 340 intake manifold with a Holley (model 1850) 600 with vacuum secondaries. I also installed a set of Hedman headers. This motor is in an automatic 73 Challenger backed by a 727 tranny.
My question is this. It seems to run fine and pull hard but I can always smell exhaust fumes. Even when it's idling the fumes are really strong, so much that you can not really stand behind the car. I've tryed playing around with the timing, but it really doesn't change. The carb was just rebuilt and again no change. I'm just wondering if it's maybe the characteristic of the cam.
Any thoughts or suggestions by anyone. It's getting to the point that I don't want to drive it anymore because of the exhaust fumes.

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Old 07-30-2004, 10:47 AM
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Sounds like it needs to have the idle circuit of the carb leaned out a bit. Is the choke fully opening when it's hot?
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Old 07-30-2004, 11:08 AM
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too much fuel. Check float, choke and primaries-

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Old 02-08-2009, 06:20 PM
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340 motor

I would pull the spark plugs to see what color they are burning. This gives you an idea whats going on. You may need to richen up plug heat range. jim
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Old 02-09-2009, 02:54 PM
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The fumes you are smelling. does it smell like unburn gas?
If it is does, you could have a leaky carb. I would check the plugs to see how they look. Your timing could be off, too. I would also check the ignition system. You could have a weak spark.
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