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235 VIDEO: Does this sound like rod knock?

Discussion in 'The Hokey Ass Message Board' started by The_Monster, Mar 31, 2012.

  1. The_Monster
    Joined: Sep 8, 2003
    Posts: 1,754


    A bit of history. My '53 chevy bel air has a '59 235 in it. I had it rebuilt by a well respected rebuild company that rebuilds early motors. you can check out my build thread here for all the info:

    The motor was rebuilt with stock specs short of a .060 bore and crank and cam regrind. It runs stock intake and single carb. Ive changed the oil, using the special "green oil" with zinc additive. I changed the special break in oil after the break in. I then changed the oil after the first 50 miles, 100 miles and 500 miles. Im just over 300 miles since the last oil change and have noticed a knock. Ive never driven over 50 MPH and never had it on the hi-way and have never ripped through the gears or pulled hole shots.

    At first I thought it was the 3 speed growling, because how could it be the motor? It was freshly rebuilt, right? I cut away my trany hump on the interior so that I could hear the trans while driving.

    My brother and I just drove it around and we recorded the audio during the drive. We also used a stethoscope to try and pin point where the sound was coming from. Turns out its not the trans at all. In fact it was pretty quiet during the entire trip. The growling, knocking sound was coming from the motor. The further up the bellhousing he put it, the louder it was.

    Heres the symptoms: At idle, it purrs. While accelerating and decelerating it purrs. However, while lightly pressing the gas pedal to maintain my speed, I get these sounds. Also, when accelerating up to 2000 RPM to shift, Ill get the same sounds. Ill also get the sounds if I stab the pedal up to about 1500 RPM while stopped and out of gear.

    Im hoping that some of you will have some advice as to what the sound is, and whats making it happen. Thanks!


    Last edited: Mar 31, 2012
  2. Hotrodbuilderny
    Joined: Mar 20, 2009
    Posts: 1,646


    It sure sounds like one, hows the oil pressure.
  3. The_Monster
    Joined: Sep 8, 2003
    Posts: 1,754


    oil pressure is 15 when cold and less than that when driving around. When it was fresh from the rebuild it was around 45 cold and 30 when driving.
  4. outlaw256
    Joined: Jun 26, 2008
    Posts: 2,023


    oil pressure kinda sucks. and its just a recording but it does sound like a rod knock.i dont think id drive it anymore. i would tear it down and lookn at everything as i tore it down. good luck. oh yeah, ive have had a engine devolepe a knock just after a rebuild. to this day i still havent figured out what the hell went wrong.

  5. F&J
    Joined: Apr 5, 2007
    Posts: 13,223


    Hard to tell with the audio on the net, but it does not sound like a rod from here.
  6. big creep
    Joined: Feb 5, 2008
    Posts: 2,945

    big creep

    yea it does sound like one to me.
  7. OldBuzzard
    Joined: Mar 8, 2008
    Posts: 878


    You would do well to check into some reasons for low oil pressure. The 45 & 30 are more like it.
  8. The_Monster
    Joined: Sep 8, 2003
    Posts: 1,754


    Thats what I was thinking. These older 235s werent the best for oiling.
  9. Rod, probably. Wrist pin, maybe??? With the oil pressure issues, I'd say rod bearing.
  10. Reman
    Joined: Jul 8, 2010
    Posts: 344

    from Florida

    Again, kinda hard to tell from the video, but a couple spots in there definately sounds like a rod. However, be aware, on those old chebby sixes a loose flywheel can sound exactly like a rod knocking. You should check that first. Those old motors sound sweet when everything is right. Good luck
  11. certainly sounds ominous !!!...time for the autopsy to be performed.
  12. The_Monster
    Joined: Sep 8, 2003
    Posts: 1,754


    The engine rebuilders are doing right by their warranty. The car has been in their bay for a week, and at the end of last week they were going to pull it and rebuild it, break it in and install it. All covered. I hope I dont have to go through this again and can just drive the car! haha!
  13. RDR
    Joined: May 30, 2009
    Posts: 1,355


    sorry to hear of the problems!.....didn't sound good
    used to short out each spark plug to find out which cyl rattled...
    Let us know what the verdict was and best of luck...
  14. little skeet
    Joined: Jan 27, 2008
    Posts: 309

    little skeet
    from huston

    sounds like a main bearing knock to me!
  15. belyea_david
    Joined: Sep 21, 2010
    Posts: 134

    from Regina, SK

    Definitely a bearing. Glad to see the rebuilder is standing behind his product. Congrats on the forthcoming rebuilt engine. Good Luck!

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