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1978 Mustang combustion issue |
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pooba2u 
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Joined: November-17-2020 Location: NC Status: Offline Points: 8 |
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 Topic: 1978 Mustang combustion issuePosted: August-26-2022 at 12:28pm |
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I have a 78 Mustang (351 - 4 barrel Holley) that runs rough (chugs and will not run but half speed at best). Had new points and plugs put in recently and the boat ran great for a few weeks...but now runs rough. Not sure if its a fuel issue (changed water/fuel separator) or a firing issue....any pointers would be much appreciated.....
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pooba2u
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CanvasVapor
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Joined: March-28-2022 Location: Knoxville, TN Status: Offline Points: 15 |
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Posted: August-26-2022 at 5:23pm |
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Recheck the gap on the points? The gap is just a starting point, better to check the dwell and adjust the points gap 'til you get the correct dwell, then check timing. Distributor advance springs failed or worn?
Fuel quality or supply issue? Gunk in the tank blocking pickup tube, or maybe tank vent or anti-siphon clogged? More description would help. Is it hard to start? Runs rough when it does start, or runs well then gets rough, maybe when hot or after a few minutes? Running rough through the whole rpm range? Have you checked any of the spark plugs? |
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MrMcD
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Joined: January-28-2014 Location: Folsom, CA Status: Online Points: 3750 |
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Posted: August-26-2022 at 5:41pm |
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Some install new points but do not lubricate the lobes. The points can wear down and start closing, leaving you stranded. Points used to come with a little lube but have not seen that in a while. Where the points rub against the distributor lobes needs a little lube. I have used a little grease with no issue. Just a film, not a glob.
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pooba2u
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Joined: November-17-2020 Location: NC Status: Offline Points: 8 |
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Posted: August-28-2022 at 10:31am |
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Boat starts ok, would run fine, then I began to notice some rough (bogging) running at higher rpms(+3000). Now the boat is consistently rough running throughout rpm range though more noticeable as rpms increase.
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pooba2u
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CanvasVapor
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Joined: March-28-2022 Location: Knoxville, TN Status: Offline Points: 15 |
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Posted: August-29-2022 at 4:33pm |
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Are you sure you're getting enough fuel? Maybe the carb has some blockage. Have good spark at all cylinders? Coil voltage? Full disclosure, I'm guessing based on lots of reading on this forum. It's gotta be one of fuel, spark, or timing. It's the bogging at higher RPMs that make me think the timing is the problem and not advancing the timing enough. Maybe a spring was failing, giving you poor running at high rpms, then broke and is now giving you a rough time throughout the whole rpm range now.  |
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pooba2u
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Joined: November-17-2020 Location: NC Status: Offline Points: 8 |
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Posted: August-31-2022 at 9:58am |
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I removed the distributor cap and lightly scraped the tip of the rotor and the distributor points. Problem solved. Boat purrs again.....Thanks to all for steering me in the right direction....
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pooba2u
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