Need Help -- Knocking 440 Sound

Engine, Trans & Driveline

  1. mvandale

    mvandale Member

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    Hi all. Not a frequent poster, but have exhausted all normal ideas on diagnosing a loud knocking sound (sounds like rod knock) in my '68 Charger, but can't find the culprit.
    The engine is a flat-tappet hydraulic cammed 440, .030 over, built by Muscle Motors (now defunct) in 2014 and only has about 1000 miles on it. It runs excellent except for the knocking sounds. I've owned only Mopars & built dozens of engines in the last 35 years, so I've got a bit of experience in them, but this one has me stumped.

    Upon engine startup, it immediately makes a LOUD knocking sound...almost like two solid pieces of wood are being hit together. The sound varies with engine speed...slightly quieter upon deceleration and it makes no difference hot or cold. The car hasn't been driver particularly hard, with few acceleration runs and all below 5700 rpm. I've chased about every possible culprit and googled every board for similar problems, but none of the fixes worked.
    The noise can be heard most clearly at the front of the block...using a stethoscope and/or "wood block" trick and you can even feel the knocking at the front engine stamping pad...across the intake hold down, by the thermostat outlet...and less on the passenger side and even less as you go towards the back of the engine. Pulling the spark plugs one at a time makes does very little for the knocking sound, BUT when the #1 cylinder wire is pulled, when you put the plug wire back into the distributor cap, the very first spark makes the knock loud...ONCE. Just like a "pop" knocking sound, and then a continuous lower knocking sound.
    Armed with that, I figured it was the rod bearing....but:
    - I have good oil pressure (~60 psi cold, ~ 30 psi hot idling). Replaced the oil pump with a Melling high volume (no change in condition); Oil changed (twice) with Valvoline VR1 10/40...and a second time with VR1 20/50, but neither made a difference in sound.
    - Pulled the oil pan & checked all the rod bearings. They are all in excellent condition, no noticeable wear (particularly #1) and they all measured between .0015-.0025" clearance. Nothing excessive or out of the ordinary. For good measure, I replaced all of the rod bearings while I was in there but the sound didn't change at all.
    - There was no metal or foreign substances in the oil pan at all;
    - Also checked the valvetrain. Nothing wrong there: all cam lobes are good, all pushrods are straight, all rocker arms, springs, valves, shafts, and assemblies are tight, not hitting, or show any signs of anything amiss.
    - Someone suggested that maybe the mechanical fuel pump and/or pushrod may be worn/bent/etc. Pulled the fuel pump pushrod and it is straight & correctly lengthed...no signs of wear or tear. Checked the fuel pump arm and pump...no issues. Even ran the engine with the fuel pump removed...same knocking sound.
    - Checked all belts, pulleys, and systems with nothing wrong there. I went so far as to run the engine with the alternator belt disconnected and then the power steering belt disconnected, with neither one affecting the knocking sound.
    - Pulled the timing cover and checked the chain & gears, but all was good with no signs of damage, wear, or other obvious concerns.
    - All valve covers, oil pans, and other areas were pulled to see if there was anything hitting, with nothing showing.
    - All exhaust gaskets & fittings were checked & or/replaced, but none of this affected the knocking sound.

    I'm at my wit's end. The sound is LOUD and definitely near the front of the engine, but seems like #1 rod bearing...but that checks out. Could #1 piston be so loose in the bore that the piston slap sounds like a bad rod? The noise has not always been there, and the car was in climate controlledstorage for 2 years (2018-2020), but everything was checked out prior to start up then.
    Help! Charger Storage.jpg
     
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    • pnora

      pnora FBBO Gold Member FBBO Gold Member

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      Did you check the flex plate and bolts.
       
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      • 1967coronet

        1967coronet FBBO Gold Member FBBO Gold Member

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        Wrist pin loose at the rod end or in the piston. WAG.
        May also want to run a compression test and see if you have a weak reading on #1.
         
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        • 69Bee

          69Bee FBBO Gold Member FBBO Gold Member

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          A cracked piston skirt can knock like that. I suspected a rod once, but it turned out to be a cracked skirt
           
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          • mvandale

            mvandale Member

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            Yes. It is an automatic, and I checked the bolts on the torque converter. All are tight, none have wear, and none are hitting anything. Ran with the inspection cover plate off too and no change. Plus, sound is definitely further away from there when I laid under it. :(
             
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            • mvandale

              mvandale Member

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              Thanks,
              A cracked piston/skirt may be the only option left (man, I hope not). I inspected the piston, rod, and piston walls when inspecting/replacing the rod bearings and it all looked good. I thought maybe if I tapped on the underside of the piston with a piece of wood it would make a different sound if cracked, but it sounded like all the rest of the pistons. Wouldn't a cracked piston be obvious...or maybe lose compression? I failed to mention that I did a compression test & all cylinders were making between 125 and 150 psi. #1 piston (where I thought sound was coming from) pumped up to 120. I suppose if the piston skirt were cracked it may not affect compression, but wouldn't it damage the cylinder walls? I noticed none of that.
               
            • 69a100

              69a100 Well-Known Member

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              You know? It'd be nice to have a video to help point you in a better direction as to what's knockin. Good Luck
               
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              • 69Bee

                69Bee FBBO Gold Member FBBO Gold Member

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                The one I dealt with worked fine, just knocked like a rod. I had to look real hard to see it from underneath the truck, and oil will also small cracks.
                 
              • mvandale

                mvandale Member

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                I'll try to get a recording & post it.
                 
              • monaco66coupe

                monaco66coupe Well-Known Member

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                I hate to be the one to say it, but The heads need to come off in order to better determine the problem.
                and Unfortunately The engine may well have come out. I would hate to see any damage being done to the Block.
                 
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                • monaco66coupe

                  monaco66coupe Well-Known Member

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                  and, it can't be any worse then hearing the cam come to a grinding halt because the the break in oil was not up to snuff. 100 miles later it was a horrendous sound. So out the engine came, and a complete flush of all the metal shaving, and complete rebuild.
                  A very painful learning experience.
                   
                • zyzzyx

                  zyzzyx FBBO Gold Member FBBO Gold Member

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                  I would go on E-Bay and buy one of those cheap endoscopes that hook up to your
                  phone or tablet and stick it down the spark plug bore to see what's going on. They
                  come with LED lights on them and can be worked around so when the piston is all
                  the way down you can get it to make a U-Turn and look at the head surfaces too!
                  Make sure the body diameter is small enough to fit in the plug hole. The pistons
                  could just be touching the head a smidgen! Good luck!
                   
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                  • pnora

                    pnora FBBO Gold Member FBBO Gold Member

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                    Thats what I was just thinking of. Maybe something foreign got in there and is wedged on top of the piston.
                     
                  • Fran Blacker

                    Fran Blacker FBBO Gold Member FBBO Gold Member

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                    With oil pan you with that endoscope, scope the wrist pin area for cracking.
                     
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                    • biomedtechguy

                      biomedtechguy Accelerati Rapidus Maximus FBBO Gold Member

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                      :popcorn2::popcorn2::popcorn2:
                       
                    • sam dupont

                      sam dupont Well-Known Member

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                      Don't know if this would work, but if a stethoscope were held to each wrist pin and the motor rocked, would a noise be detectable?
                       
                    • steve from staten island

                      steve from staten island FBBO Gold Member FBBO Gold Member

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                      I had a cracked piston skirt that went into the oil ring once. Blew oil out the breather, smoked. Since you said you looked at the walls of number one, im thinking a wrist pin
                       
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                      • mvandale

                        mvandale Member

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                        The video & audio of the noise...

                         
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                        • monaco66coupe

                          monaco66coupe Well-Known Member

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                          This may be a shot in the dark, but maybe it is related to the timing chain and/or gears?
                           
                        • pnora

                          pnora FBBO Gold Member FBBO Gold Member

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                          I believe I hear two noises. One sure sounds like valve train. The other might be piston. The one clue is what you said about pulling the spark on number one and how it changes when you put the wire on. You could run it with the left valve cover off to see if anything can be seen. You could unhook the coil and see if you hear anything while cranking it. You sure do not want to run it like that.
                           
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