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02-24-2012, 03:23 PM | #1 |
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Join Date: Apr 2011
Posts: 350
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Help on noise please
Iam very new to the flathead motor. I have a 59ab with alum heads, alum intake with holley 4 barrel, been hearing a light popping noise and rough running on acceleration and some times at idel, started to investigate what might be wrong. Did compression check, 155 +/- all cyl. Adjusted carb, thinking its fuel related, and replaced many parts on it. ignition is as it was when running well (electronic), wires all good. Tightened down bolts, nuts, hoses for vacuum leaks, OK. Vacuum gauge shows very very slight flutter. Will run well for a short period then start popping again. Isolated problem to rear cyl. drivers side (removing plug wire while idle and no change in rpm). Popping sounds mechanical to me. VALVE SPRING ???? Will a valve spring "climb/rotate" and work well for a period of time then let go and then re position itself in a sort of cycle?
Any help would be appreciated, Thanks guys. Frederic |
02-24-2012, 04:29 PM | #2 |
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Location: new jersey
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Re: Help on noise please
very rare but i have had a bad cam lobe do the same . is more on an excel then anything else, if cam has an issue. could also be a sticky valves too.
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02-24-2012, 08:20 PM | #3 |
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Re: Help on noise please
check valve clerance if it,runs ok when cold then starts poping when hot it could be clearance is to tight as the valve heats it expands also guide could be tight . take the intake manfold off it,s no big deal & check
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02-24-2012, 08:27 PM | #4 |
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Re: Help on noise please
frederic>>>Did compression check, 155 +/- all cyl. >>>
Hmmmm? Are those psi, kPa,?? Jack E/NJ |
02-24-2012, 08:31 PM | #5 |
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Posts: 350
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Re: Help on noise please
I did not look at the psi or kpa when i looked at it. i was looking for consistent readings. Will take off intake and check clearance but i was under the impression one could not adjust flat head valves. I assume these are original style.
thanks |
02-24-2012, 11:44 PM | #6 |
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Re: Help on noise please
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02-25-2012, 11:25 AM | #7 |
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Re: Help on noise please
It sounds like the guide keeper has slipped out of place or been installed wrong.
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02-25-2012, 01:00 PM | #8 |
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Location: Coral Springs FL
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Re: Help on noise please
I know this may seem remote, but install a new plu in that cylinder and see what happens. Maybe the plug is fouled and not fully burning the gas.
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02-25-2012, 01:30 PM | #9 |
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Location: Florida and Penna.
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Re: Help on noise please
frederic, Sounds like you could have a few sticky valves. this is normal with this new gas. Get a quart of Marvel Mystery Oil and drizzle some down all the throatle plate holes while it is running keeping your hand on the throatle to keep it running. Use about a 3rd of the bottle, put the rest in the gas tank and drive it about 10 or 12 miles and see how it acts. You need to put about a pint in the gas tank every other time you fill up or the valves will stick. G.M.
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02-25-2012, 01:32 PM | #10 |
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Location: Gerrardstown, WV
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Re: Help on noise please
I try to use 4 oz at each fillup.
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02-25-2012, 11:12 PM | #11 |
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Join Date: Jul 2010
Location: Kentucky
Posts: 127
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Re: Help on noise please
fREDERICK Checking a cylinder by pulling a plug wire off can cause damage to electronic ignition components .You can use a plug wire that is pulled off and attach it to a plug touching the motor no problem.A plug wire pulled off and not touching a ground (motor or frame) can cause the coil to break down and more likely with electronic ignition because of the higher voltage. Just a word of caution Lee34
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