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Thread: Possible rod knock - HELP!

  1. #1
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    Question Possible rod knock - HELP!

    Alright, here's the scenario. I bought a 94SC. I was told it had a rod knock , and that the previous owner had been driving the car for the longest time with this knock also. Now, does an engine with a knock, make noise at all rpms ? I'm iffy to beleive that this sc has a knock, because the knock sound comes in between 2500-3000 rpm, it chooses, its not specific, and the car has plenty of power. I'm thinkin it could be a bad balancer, as there is drivetrain vibrations also. It also shudders when in drive and the rpms drop to 500rpm. I'm gunna start wrenching tonight, hopefully find something out . Any help is greatly appreciated. I know someone out there has answers.

  2. #2
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    cracked flexplate
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  3. #3
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    Talking get out your DR. tools

    Start the engine and start to listen to the noise, use a stefiscope[spelling] and move around to see where the noise is coming from. I had one that was something like what you are talking about, and it was the blower. Changed it out and the noise was gone. A rod knock will be it's loudest at morning startup's. That is when there is no oil to quiet it down.... They also sound more on the bottom of the engine. You can also use a long screwdriver to listen as well. Please be careful when you are putting the end of the driver on the engine. place the other end[the big end] to your ear and you will be suprised at all the things that you can hear...Good luck and if it is bad you can always sell it to me.........Rich
    Too many cars,too little time to drive them. Anything less than 500 cubes is a small block. If you slow down in life you will get run over..

  4. #4
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    Well I appreciate the help guys. Hopefully tomorrow, I can tear into it. I really have my doubts that it is a rod knock, especially being that the prior owner drove it for quite some time in its current condition. One of my friends said that the shudder at low rpms coud be the torque converter starting to go, as that happened to him in his lx v8 bird. I'll update everyone when I know something.

  5. #5
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    The easiest way to tell if it is a rod knock without really doing anything or tearing anything apart is simply to give it a quick rev (stab) in neutral fom 2000-3500 letting off just as quickly. This requires no boost or high reving of the engine. A rod knock will be silent on accelleration and will knock on decelleration. It will also be more noticable when the oil is hot vrs oil cold. A motor can run a long time with a rod knock. I had a SBC that I drove the begeebers out of for a whole summer that knocked so loud it scared my passengers.

    On the other hand failure could be iminent.
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  6. #6
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    my connecting rod bearing went, and boy was it loud, it got louder and louder on my way home, i was afriad to find out what it was this was (like 3-4 yrs ago) and my brother took out my engine and checked it, he showed me one of my rods and u could jiggle it. but it was loud at startup and even louded with a little gas, because my main bearing was shreded so it was hitting metal to metal (was really loose)... Alex L

  7. #7
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    Well, on startup, it sounds like someone coughing while clearing there throat, but that's only for about 2 seconds. Then the car will run dead silent. The car makes the noise on acceleration and de-acceleration. Noise will come in anywhere between 2200 and 3100, its not a set rpm where it starts. I checked the balancer, all is good. Fired the car up with no belts on, still make the noise. It's really bugging me. Oh, and the sound is the same at all engine temps.

    Damon- any easy way to check the flexplate without dropping the tranny?
    Last edited by pearl95sc; 04-04-2004 at 02:47 PM.

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