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Slight engine knock

 
jmoudry
User
Posts: 63
Joined: 06/08
Posted: 11/20/10 06:40 PM

Hello
I have a 66 289 auto that has a very subtle knock at idle.  It seems like the knock is louder on the passenger side.  I cannot hear the knock while driving and when I raise the rpm on the engine while listening under the hood I cannot hear it anymore.  I tried probing around with a bearing stethoscope and cannot find where it is coming from.  All I hear is the noise of the rotating assy.  Does the 289 usually have some light knock/tapping at idle?  The previous owner said that the engine has 20k on a rebuild.  It runs real strong and does not have any leaks.  

Video link:  http://www.youtube.com/watch?v=QBdtcIUxVIQ

Thanks  
66 289 coupe

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Gregski
Enthusiast
Posts: 475
Joined: 03/10
Posted: 11/21/10 10:14 AM

no idea, you are on the right track with the stethoscope, maybe get a buddy to press the gas pedal when you're under the hood listening, but I would check compression maybe that will point you to a bad cylinder, which could be a clue to what's loose in there maybe

also maybe take off the belts and run the car for a little bit to eliminate the unlikely possibility that it could be an accessory such as power steering, ac, alternator, etc making the noise

I'm reaching here trying to give you some semi amateur advice, LOL

and please let us know when you find it, and how you found and fixed it, so we all benefit from your misery, hee hee  

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jmoudry
User
Posts: 63
Joined: 06/08
Posted: 11/21/10 10:43 AM

Thanks for the reply.  Hope someone has heard this before.  I was hoping that I was being paranoid.  
66 289 coupe

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jc65coupe
User
Posts: 197
Joined: 09/09
Posted: 11/21/10 01:36 PM

it does not sound like anything to be concerned about at all, maybe a little valve adjustment is in order but from what I was able to hear, not much from my crappy speakers, sounded decent. It appeared to idle smooth by what I could see so I would just just pull the valve covers and check everything.  

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jmoudry
User
Posts: 63
Joined: 06/08
Posted: 11/21/10 03:42 PM

Great I was hoping it was just valve train noise.  I thought that my previous 289 sounded similiar but I could not remember.  
66 289 coupe

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waynep7122
Guru
Posts: 774
Joined: 01/10
Posted: 11/21/10 04:15 PM

i bet i can make it go away......

where the spark plug wires go over the drivers side valve cover....

change the order in the holder....

this is a problem on most small block fords... 302, 351W...

the driver side cylinders are    5, 6, 7, 8,

the 7 and 8 cylinder fire only 90 degrees of crank rotation apart...  so the 7th cylinder is firing when the 8th is half way up with compression building and a charge of fuel...   with the 2 cylinders next to each other and running all the way from the cap to the cylinders... its possible and it has been proven that induction from the high voltage spark going down one wire .. will INDUCE a spark in the wire next to it, if it runs side by side long enough...

so.. reroute your spark plug wires on the wire holder on the drivers side valve cover...

put them in this order...

7, 5, 6, 8...  and see what happens...  i am not telling you to unplug them at the cap or at the spark plugs... but .. just out of the holder... and repositioned...

there are TSBs on this... for the later models...

i can find it and post a link to it...


failure to do this will result in a damaged piston and cylinder bore..... as the piston will be running lean and it will melt the piston to the cylinder wall.. resulting in a loss of compression and excessive oil consumption...

HOW many other people have heard of this...




Spark Plug Wire Routing & Firing Order TSB 94-04-10 for 87-93 5.0 & 94-96 5.0 & all 5.8 - engine miss, spark knock, buck/jerk, surge and other driveability concerns; MIESK5 NOTE; The firing order for 1987-1993 5.0Ls is 1-5-4-2-6-3-7-8. If #7 and #8, or #2 and #4 spark plug wires are routed next to each other at the separation bracket, an induction crossfire condition can occur. & The firing order for 1994 5.0Ls & all 5.8Ls is 1-3-7-2-6-5-4-8. On these vehicles the #1 and #3, or #5 and #6 spark plug wires must be separated to eliminate the possibility of an induction crossfire. To eliminate the possibility of the coil wire becoming disconnected, route the coil wire under the spark plug wires at the distributor cap.  

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waynep7122
Guru
Posts: 774
Joined: 01/10
Posted: 11/21/10 04:30 PM

this is even better... it is the PDF of a TSB... and it shows the exact spark plug wire routing...

http://ww2.justanswer.com/uploads/eppic60/2009-08-08_165020_tsb94-04-10-spark_plug_routing.pdf


this is a must read for all ford V8 with distributer owners.... its only 8 pages...



knock knock...      

who's there???

spark knock....

spark knock who....

spark knock tearing up your pistons......  

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jmoudry
User
Posts: 63
Joined: 06/08
Posted: 11/21/10 05:41 PM

wow ever the original shop manual has the 7 and 8 on opposite sides.  Thanks for the advice I will give it a try.  
66 289 coupe

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jmoudry
User
Posts: 63
Joined: 06/08
Posted: 11/21/10 05:55 PM

I changed the wire order still have the noise.  The more I listen to it the more it seems like it is coming from the front of the engine.  Maybe noisy fuel or water pump?  
66 289 coupe

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palmbeachmustangs
New User
Posts: 10
Joined: 05/10
Posted: 11/21/10 06:58 PM

Hello All. Well I have read all the post and I may be of help.

#1 if you have listned to the motor well with the theiscope and didnt hear it then i Have a sujestion.

    I restore old mstangs for a living and have for over 25 years www.palmbeachmustangs.com and have found a lot of times that noise could be a loose flywheel eaither converter to flywheel or flywheel to crank.

    Iv even seen cracks around the flywheel bolts due to not using the big ring washer that all the bolts go through before going through the fly wheel.

     This has caused knocking at low speeds and idle. Iv has customers say its been making that sound for a long time???  Who knows how long it will hold on when this happnes but it seems like it will go on for a long time before causing a lot of damage.

       Just for kicks ck converter to flywheel bolts. Remove 1 and see if the hole is rounded out. If so replace it. Then ck flywheel. Take a pry bar and pry it away from the block and see if it has any play in it.

      And 2 more dumb things to ck. Fuel pump. Yes i know but belive me iv had fuel pumps that made knocking sounds at idle.

      And once i hade a oil pump new knock in a new motor and it drove me crazy!!


        If it isant rods/crank/rist pins/ or mains theses are a few good places to start.

Good luck

Bryan

www.palmbeachmustangs.com  

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jmoudry
User
Posts: 63
Joined: 06/08
Posted: 11/21/10 07:11 PM

The noise did seem to be louder at the fuel pump.  The pitch is shifted theough the scope so it is harder to distinguish.  
66 289 coupe

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jmoudry
User
Posts: 63
Joined: 06/08
Posted: 11/21/10 07:13 PM

other than tearing the engine down how can I verify that it is not the mains/rods or pistons?

Just wondering if everyone took a listen to the video link that I posted?
Thanks  
66 289 coupe

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jmoudry
User
Posts: 63
Joined: 06/08
Posted: 11/23/10 08:52 AM

Anymore input?  
66 289 coupe

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palmbeachmustangs
New User
Posts: 10
Joined: 05/10
Posted: 11/23/10 07:41 PM

well if tis a rod or or rist pin then you can just remove 1 spark plug wire at a time and listen to the noise. Do 1 at a time!! This will let the presure off of the rod/ristpin during firing reliving the presure off the piston at that moment of fire and will not knock any more. I know it sounds crazy but it works for me.  

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jmoudry
User
Posts: 63
Joined: 06/08
Posted: 11/23/10 09:22 PM

should I leave the engine running and pull one plug at a time or shut it down between plugs?

Forgot to mention that my oil pressure averages in the middle of the guage and the dipstick shows in the middle of add and full.  So the oil pressure seems dead on.  Prob a good sign that the there are no serious issues with the mains?

Thanks  
66 289 coupe

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