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Rough idle, gas smell
https://slantsix.org/forum/viewtopic.php?t=22259		 Page 1 of 1
Author:  Guest [ Wed Mar 14, 2007 9:27 pm ]
Post subject:  Rough idle, gas smell
Hello,
I have a 71 dodge dart with a 225 slant six.
The car has developed a rough idle, its not incredibly rough, but it is annoying. Also the car smells like gas after I turn it off. If I shut off the car and come back 15 minutes later and try to start it, it has to turn over several times before it fires, like it's flooded or something.

Once I noticed these problems, I wanted to do some upgrades. I bought a new Holley 350cfm 2bbl carb from Jegs. I put in an electronic ignition kit off a 78 Aspen all new parts, along with new cap/rotor/plugs/wires. I had a mechanic check everything, time it, and adjust the carb.

The car runs better, a lot more power, however the idle is still rough. My mechanic says that some of the valve seats may be worn, because the car runs great when driving, only rough at idle. The car also smells like gas after i shut it off. To add more detail to this possible flooding, if i shut off the car and go start it up 5-10 minutes later it's fine (allthough smells like gas). If i go back 15-30 minutes later it has to turn over SEVERAL times before firing.

Does anyone have any idea what this is? It's so strange to still be there even after the electronic ignition/new carb.

Thanks!
Author:  DusterIdiot [ Thu Mar 15, 2007 6:54 am ]
Post subject:  Pull plugs...
So after setting up the carb and everything did you pull the plugs to see if it's rich (black/sooty/ or wet)?

Another thing to worry about it 'percolation and boiling'...if the heat riser is stuck or you have baked the underfloor of the intake plenum, the heat can boil the gas in the carb bowl...and in a holley it can "puke" a large amount of gas out the boosters if that occurs during heat soak (most emission carbs have a purge/bowl vent hose to prevent this an return that stuff back to the gas tank...)

???

-D.Idiot
Author:  Guest [ Thu Mar 15, 2007 7:28 am ]
Post subject: 
I removed the butterfly valve when installing the exhaust manifold, so I don't think there can be a boiling problem.

When I took the old plugs out, they were fouled black.

Could it be possible that the fuel pump is leaking into the crank case, and the fuel vapors being sucked into the PCV valve is whats causing a rough idle? That may also explain the gas smell.
Author:  supton [ Thu Mar 15, 2007 9:00 am ]
Post subject: 
Very possible. What does the oil look like? Does it smell like gas? IIRC, if this happens, the motor tends to blow blue smoke too (easier for oil to leak past rings).
Author:  SlantSixDan [ Thu Mar 15, 2007 9:06 am ]
Post subject: 
Quote:
I removed the butterfly valve when installing the exhaust manifold, so I don't think there can be a boiling problem.
H'm. Why did you do that? Removing that valve causes boiling problems!
Quote:
Could it be possible that the fuel pump is leaking into the crank case, and the fuel vapors being sucked into the PCV valve
Certainly, that's possible. Also remember that in '71, the fuel tank and carb bowl vent to the crankcase via hoses to the crankcase breather and fuel pump body, respectively, so if there's any condition that would cause more than normal fuel vapours, it'll cause and/or aggravate hot start/hot idle problems.

Your mechanic's "valve seat" guess is not a good one.
Author:  Doctor Dodge [ Thu Mar 15, 2007 9:23 pm ]
Post subject: 
Have you checked the valve lash?
DD
Author:  Guest [ Fri Mar 16, 2007 11:49 am ]
Post subject: 
Good idea I will check my valve lash again.
In your guys opinion, what should I set the valves to? Intake and exhaust.

Thanks
Author:  Dart270 [ Fri Mar 16, 2007 12:52 pm ]
Post subject: 
0.010" intake, 0.020" exhaust. Make sure you set them when the engine is hot.

Lou
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