Need help on engine noise
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Freshman User
Joined: Oct 2008
Posts: 25
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From: Cedar Creek Texas
Need help on engine noise
i just put a new 390 in my truck and ive noticed that when it is under a load or goin up a hill or accelerating at highway speed to even faster aka 70 to 80 it starts a bad tapping noise from the top end until i ease off the gas.if i punch the gas hard it does it to. i replaced the pushrods,adjusted the timing to 10 12 and 14 degrees btdc (a week on each),still did it, put two different new sets of lifters in after soaking them in 30w and atf for 24 hours. could it be the cam or the cam lobes getting worn?? i even tried using another set of rocker arms(the nonadjustable types like the ones on there now) and it didnt fix it. i have no idea and its stumbling when it taps. it is not a spark knock i dont think seeing as its got a new distributor and coil and ignition module, what yall think it could be? appreciate the help. kind of makes a light metallic noise nothing real heavy duty just a loud rapping noise. engine makes 40 to 45 psi at 2000-4000 rpm and 15 to 10 psi at idle when hot
Senior User
Joined: Mar 2009
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drain out a quart of oil and replace it with a quart of lucas oil, i did that with a rice burner that sounded like it was going to rattle apart with just plain 10w40 but after i put the lucas oil in it she pured like a kitten...it sertainly wouldnt hurt your engine and it would eliminate dry starts as well.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Replacing the coil and ignition module has nothing to do with spark knock. Spark knock is a condition caused by a lean fuel mixture and over-advanced timing. You have wasted a lot of money my friend. Can you describe the sound more? If it was lifters, it would show up at all RPMs and follow the engine speed. Spark knock only happens under a load, and sounds like marbles in a can. Your oil pressure is fine and your lifters are fine; it sounds like pre-detonation (spark knock).
New User
Joined: Mar 2009
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From what you describ, sound like spark knock.
Try higher feul quality, mostly cures pings, see if noise changes. Double check timing! I know you already did, but its always a good thing to check serval times, lol. You can tell i've gotten burnt on that one. Richen up your carbs!
Give us other symntoms
Try higher feul quality, mostly cures pings, see if noise changes. Double check timing! I know you already did, but its always a good thing to check serval times, lol. You can tell i've gotten burnt on that one. Richen up your carbs!
Give us other symntoms
Postmaster
Joined: Oct 2008
Posts: 3,026
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From: Renton, WA
12 as a base timing isn't alot, you need to look at the total timing when the rpms are up, Fords are natorious for having to much total timing, to fast, check it with the vacuum line unpluged.
What kind of carb, sounds like you should richen it up under load?
Senior User
Joined: Oct 2006
Posts: 236
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From: Tacoma Wa.
Sounds like you have a bad valve spring try changing them out can't hurt,but mine did the same thing and I ended up going with rollers and new rods. you get springs for around a $100 try Jegs and Summit
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From: Renton, WA
Laughing Gas
Joined: Jan 2007
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Does it make the noise in nuetral/park? If not then its detonating man! get it fixed immediately or you'll pop the head gaskets and need the block and heads decked flat again........or you'll break rings or even break/burn up valves/pitons! Pinging=disaster soon!
Likely a timing issue.......could be a fuel issue as well. Check the fuel pump where it rides on the cam (could be heavily worn). Also, I'm assuming you have a mechanical temp gauge.........If it's running way hot it can cause pinging under load as well as well.
good luck. Find your problem fast!!
Likely a timing issue.......could be a fuel issue as well. Check the fuel pump where it rides on the cam (could be heavily worn). Also, I'm assuming you have a mechanical temp gauge.........If it's running way hot it can cause pinging under load as well as well.
good luck. Find your problem fast!!
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Freshman User
Joined: Oct 2008
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From: Cedar Creek Texas
howdy yall, so i set the timing to 8 btdc just now and it doesnt do it but maybe once or twice when the pedals to the floor. should i try 6 btdc. its like im driving a different truck haha. i dont know what happened because it was on 18btdc (woah ****) when i just checked it. maybe this distributor slipped?? dam i dont know the bolt wasnt that tight but it wasnt loose either oh yeah it has an edelbrock 1406 on it
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Freshman User
Joined: Oct 2008
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From: Cedar Creek Texas
if cam was flat the engine wouldnt run, if it could somehow run it wouldnt idle which it does.
Posting Guru
Joined: Nov 2008
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From: wyoming
Once had a similar problem with a 360 and the problem was a crank was wrong. Meaning on journal was ground offset and some of the pistons were .005 out the hole and some were .003 inside the cylinder. One cylinder was detonating and later figured it out with good fuel stopped detonation. One cylinder was around 12 to 1 and the rest around 10 to 1 compression. Installed another crank and check deck height and all were around .003 in hole like it was supposed to be. On the inital set up we just checked one cylinder on each bank and decked block off of those numbers and should have check them all. never seen this again with a ford FE engine.