Calling all Mechanics/Shade Tree Mechanics - Rod Knock or Bad Lifter?

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  • FWP9MM

    Sharpshooter
    Rating - 100%
    9   0   0
    Aug 22, 2010
    437
    18
    Bluffton
    I bought 2000 Malibu from a guy on one of the forums I frequent (60DegreeV6.com - Site News). This car was his project for 3 years, in which he indicated that he recently got it all back and after 45 minutes of run time the engine developed a rod knock. He has other projects and lost interest after the "rod knock" developed and sold me the car at a loss for $2,000.

    Engine Mods List:
    3.5L V6 engine engine from a Pontiac G6 that had a complete tear down and inspection,new rings and bearings,multi angle valve job,1280 cam grind, tce double roller timing chain,ported upper and lower intake,tce 65mm throttle body,tce crank trigger,S&S ceramic coated headers,cold air intake,lt1 lifter springs,180 stat,LS1 MAF, ARP Rod Bolts, Aeromotive 340 fuel pump, tune VCM by Sinister Performance, ect. This is all new and assembled by a professional shop in Ohio, in which he provided me with a receipt which indicated $1,600 in machine work/labor for assembly.

    Trans:
    4t45e from 03 ga ,completely rebuilt, raybestos blues,LSD from engineered tech,3.91 final drive ratio,3000 stall converter

    Where I am at now with the car:

    I got the car over to my house on Thursday and when I pulled the front valve cover, all springs were good, rocker arms were tight, but the intake pushrod on cylinder #5 had popped out.

    IMG_0628.jpg


    IMG_0630.jpg



    I pulled the rocker arm and checked to see if the pushrod was bent, which it was not. I proceeded to put it back together started it for a short time without the valve cover, which it started and was splashing a little oil on the headers. So I shut it down and put the valve cover back on so I could let it run without splashing oil on the headers. The engine runs, and sounds sounds good, until it drops down to low idle RPM. When it drops to lower rpm the engine surges slightly and audible knock occurs. Bump up the RPM to about 1000-1200 and it goes away instantly. I took a video of this in hopes to get some ideas/advice before I tear into it any further.

    Click Image For Video


    So what do you think it is.... Lifter or Rod Bearing?

    I am leaning toward/hoping it is a collapsed lifer due to the following:
    The knock sounds like it is coming from cylinder 5, upon initial inspection cylinder 5 intake pushrod had popped out, however rocker arms were tight and valve springs were good. Everything is put back and it still knocks at low rpm, but the knock goes away with slightly higher at 1000-1200 rpm. Lastly one of the mods that was done was LT1 lifter springs, potentially meaning that it did not get put back together properly.
     

    Brown

    Sharpshooter
    Rating - 100%
    2   0   0
    May 27, 2009
    552
    18
    Brownsburg
    Put a small load on the engine. Put the car in drive, foot FIRMLY on the brake, give it a little throttle. If it is a rod knock it will sound louder .sometimes it seems to transfer the noise to the lower end of the engine.
     

    stephen87

    Grandmaster
    Rating - 100%
    22   0   0
    May 26, 2010
    6,658
    63
    The Seven Seas
    Without actually looking at the car, I can't tell you. However, I will say that is probably the best looking Impala of that body style that I have EVER seen.
     

    Hop

    Grandmaster
    Site Supporter
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    16   0   0
    Jan 21, 2008
    5,084
    83
    Indy
    Also pull one plug wire at a time and put a load on it. You'll notice less knock on the rod with a bad bearing.
     

    remauto1187

    Shooter
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    1   0   0
    Aug 25, 2012
    3,060
    48
    Stepping Stone
    That is without a doubt a ROD knockin the hell out of the crankshaft! Pull one spark plug wire of its spark plug and start engine. If the sound goes away or almost totally goes away, its that cylinders rod bearing.

    Drain the oil and pull the oil filter....you will find metal remnants of the rod bearing in there.

    Good luck with all that! Get your wallet out!
     

    BGDave

    Master
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    206   0   0
    Sep 15, 2011
    2,659
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    Beech Grove
    That is without a doubt a ROD knockin the hell out of the crankshaft! Pull one spark plug wire of its spark plug and start engine. If the sound goes away or almost totally goes away, its that cylinders rod bearing.

    Drain the oil and pull the oil filter....you will find metal remnants of the rod bearing in there.

    Good luck with all that! Get your wallet out!
    I'm with you, all the way.
     

    FWP9MM

    Sharpshooter
    Rating - 100%
    9   0   0
    Aug 22, 2010
    437
    18
    Bluffton
    I pulled the plug wire, in which the knock did not change.

    I plugged the spark plug wire back in, put the car in gear with my foot on the brake and the knock goes away completely. Gave it a little gas with my foot on the brake and it revs up without any knock.

    The prior owner had to tear down the lifters to put in the LT1 lifter springs, so my guess is that for one reason or another the hydraulic lifter is not holding. I have a spare set of lifters in the garage as well as another short block, so basically if I tear the intakes off and swap out lifers I am only out a gasket set and a few hours of my time if I get it back together and it still knocks with new lifters.

    Update:

    I pulled the valve cover again and noticed the following.

    All the pushrods were still in tact, however the pushrod that previously popped out is not getting oil and from what I can barely see the cup in the lifter is bone dry.
     
    Last edited:

    remauto1187

    Shooter
    Rating - 100%
    1   0   0
    Aug 25, 2012
    3,060
    48
    Stepping Stone
    I pulled the plug wire, in which the knock did not change.

    I plugged the spark plug wire back in, put the car in gear with my foot on the brake and the knock goes away completely. Gave it a little gas with my foot on the brake and it revs up without any knock.

    The prior owner had to tear down the lifters to put in the LT1 lifter springs, so my guess is that for one reason or another the hydraulic lifter is not holding. I have a spare set of lifters in the garage as well as another short block, so basically if I tear the intakes off and swap out lifers I am only out a gasket set and a few hours of my time if I get it back together and it still knocks with new lifters.

    Update:

    I pulled the valve cover again and noticed the following.

    All the pushrods were still in tact, however the pushrod that previously popped out is not getting oil and from what I can barely see the cup in the lifter is bone dry.

    If a lifter is collapsed then that pushrod WILL NOT get oil.
    You know you can get new lifters individually from autozone, advance, etc. I would NOT put used lifters in there.

    Also you have to pull each spark plug one at a time (you should always have 5 spark plugs hooked up each time) to make sure you get the right cylinder. Theory is that you will take the load off the rod bearing when running a dead cylinder (spark plug wire pulled). If the sound goes away then its a rod bearing, if it stays after EACH cylinder plug wire is pulled then its most likely a lifter. (lifter is still operating even when the spark plug wire is pulled)
     
    Last edited:

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