rough idle on 390

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May 31, 2009 | 06:47 AM

steve100

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5th Wheeling

Joined: Aug 2006

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rough idle on 390

hello I have a 76 supercab with a 390 that idls rough but smooths out to sewing machine smoothness going down the road. here is my list of things to check ; plugs ,wires dis cap, vacuume leak, and compression test for possible burnt valve or head gasket, if there is any thing else i should check please let me know for all of you know more about this than i do thanks for your help

May 31, 2009 | 10:59 AM

GA76Explorer

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Joined: May 2009

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Could be a choke problem i would check it out

May 31, 2009 | 11:51 AM

sc00ter

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Joined: May 2007

Posts: 150

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burnt valve, compression, head gasket etc will make it run bad all the time. Start with checking ignition timing, checking for vacuum leaks, and carb adjustment. Good luck.

May 31, 2009 | 06:05 PM

montana1967

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Joined: May 2009

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Personal experience from a past 390 owner. Put a carter 600 carb on and new distributor with dual points or a pointless dist. Check compression and do a leak down test. I brunned up a piston up before i got it right. Pluss it will improve performance and fuel mileage.