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350 Mag engine miss

Old 08-08-2011, 05:45 PM
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Default 350 Mag engine miss

I have 94 sea ray with a 350 mag and the engine has a miss. I changed the plugs(one was bad) and the fuel filter(which was clogged with crap). It runs better but still not right. There is a small peck at idle that you can hear in the second video, but goes away with any throttle input. I put a vacuum gauge on it this morning and this is my results.
There is a small amount of "blowby" coming from the pcv valves. thoughts?
http://i868.photobucket.com/albums/a...d/634fe181.mp4 http://i868.photobucket.com/albums/a...d/07750509.mp4
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Old 08-08-2011, 06:01 PM
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There is no PCV valve on your engine.
I suggest a compression test (not a leak down test). You should have around 155 pounds in all cylinders, warm engine. You may need a valve job if an exhaust valve is not seating. Don't skimp on the valve job. It is the most important part of the engine!
Dennis Moore
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Old 08-08-2011, 06:09 PM
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is it possible that the fuel filter being clogged caused a lean condition and galded or burnt a piston? here is the #2 plug. the rest of them were clean as a pin.

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Old 08-08-2011, 07:19 PM
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Fuel injected or carb? If its EFI one of the injectors might be flowing poorly or have a poor spray pattern.
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Old 08-08-2011, 07:27 PM
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a compression test will tell you if every thing is good, a melted piston will just always be dead, a constent miss at every rpm
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Old 08-08-2011, 07:30 PM
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its a carb engine, 4bbl weber. its running on all 8 now, just a little rough. I have a cap/button, and carb kit ordered for it. I'll do the compression test in the morning.
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