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Valve clater noise

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by ftn96, Oct 16, 2001.

  1. ftn96

    ftn96 1/2 ton status

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    Ok, its a stock 90 TBI and I run Exxon regular. And when its say in the bottom end of 3rd and and I give it some mo gas to get going up a hill while runnign low R's I get valve clattering or something of similar sound.
    What are the first things I can look for or do to rid this noise?
    I haven't done a tune up in a while. Anything else I can look into? OTher than a head job. Thats part of the new motor build up over the winter.

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  2. ben794X4

    ben794X4 Registered Member

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    Run premium. It sounds like you have a detonation problem I had the same thing switched to premium, all better now. you can also retard the timing but that alone usualy doesn't cure the problem. My friends who are real mechanics always tell me I can either pay for the good gas or pay for the repairs. Chevron 92 cured all my clattering problems.

    Subvert the accepted paradigm.
     
  3. ftn96

    ftn96 1/2 ton status

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    I've heard much of the term detenation. What is a good definition and or cuase for this?

    I brought my pencil, gimmie something to right on. [​IMG]

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  4. ben794X4

    ben794X4 Registered Member

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    Octane rating is basically a scale for detonation resistance the higher the number the greater the resistance to detonation. Detonation occurs when the fuel is ignited before the piston reaches tdc and is ignited by compression rather than the spark plug this is particularly noticable when the engine is under load. I also noticed it in mine at highway speed 75 or so. The results of letting this go is bad burnt valves holes in pistons etc. the oly way I know of to get around this is to run premium or lower your compression adjusting the timing can also work but will only be a stop gap method.

    Subvert the accepted paradigm.
     
  5. Stoopalini

    Stoopalini 1/2 ton status

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    Well, if he's running a TBI setup, then there should be a knock sensor to guard against detonation.

    The knock sensor listens for detonation, and if it hears it, will retard timing to stop it from happening. If you are in fact getting detonation, this is a very BAD thing.

    Are you getting any codes from the ECM? (ie. does your check engine light come on?) If it's detonation, you should be getting a code from the ESC lead into the ECM.

    I would try higher octane first, and if you still have the problem, maybe adjusting the valves will help.

    Let us know,

    Thomas.

    WooHoo, I just made <font color=blue>Trail King</font color=blue> .. LOL

    -- '84 1-Ton Blazer --
    When the goin' gets tough,
    the tough go 1-Ton [​IMG]<P ID="edit"><FONT class="small">Edited by Stoopalini on 10/16/01 11:15 AM.</FONT></P>
     
  6. ftn96

    ftn96 1/2 ton status

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    Ok, now aren't there cams out there that create a faster scavanging effect that would help prevent this or is this the fuel that is whating to be ignited by the spark that we are talking about here?

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  7. ftn96

    ftn96 1/2 ton status

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    No codes. But hell my code light bulb could be out. I need to trip the puter to see if the damn light even works. I cant remember if it comes on when I turn the ignition or not.
    I'll try the gas first. LOL! After this full tank.

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  8. Stoopalini

    Stoopalini 1/2 ton status

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    Well, the racing guys I hang out with are always very concerned with detonation because most of them run some sort of power adder (blower, NOS, etc ...)

    To reduce the risk of detonation, they richen the mixture up; but you get the best performance with a lean mixture. So the trick is to get it as lean as you can, without causing detonation at high RPMs under load.

    So technically, a bad O2 sensor could cause the mixture to be too lean and in turn cause detonation.

    I've never heard of a cam that would alleviate this, but maybe there is one out there??

    Thomas.

    -- '84 1-Ton Blazer --
    When the goin' gets tough,
    the tough go 1-Ton [​IMG]
     
  9. ftn96

    ftn96 1/2 ton status

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    Well, I wasn't necessarily talking about getting a cam just for this. But more so for when I rebuild the motor to replace this one, I was wondering if the scavaging effect of some cams would help prevent this in the future when the new motor rolls over 100k

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  10. Stoopalini

    Stoopalini 1/2 ton status

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    Hmmm, that's a good thought ...... I never considered that solution before.

    For a new motor, that will rev over 100k, a custom Eeprom is really the way to go. You can custom tune the fuel curve to give you a richer mixture up in the high RPM range. This is usually what the racers will do to protect against detonation.

    Are you going to stick with TBI after the rebuild?

    Thomas

    -- '84 1-Ton Blazer --
    When the goin' gets tough,
    the tough go 1-Ton [​IMG]
     
  11. chevyracing

    chevyracing 1/2 ton status

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    Detonation is the single most worst thing you can do to an engine with the possible exception of running sand in the block instead of oil.

    John

    Like to go sloppin' 'round in da mud in a rapid fashion....=) [​IMG]
     
  12. ftn96

    ftn96 1/2 ton status

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    I was talking about 100k miles. [​IMG]

    Yep, keeping the TBI.
    Im gonna be doing the slightly mod stock 350. Heads re-worked, slightly larger bump stick, K&amp;N, headers, stock TBI and thats about it.

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  13. Stoopalini

    Stoopalini 1/2 ton status

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    LOL .... for some reason, I was reading 10,000 rpms [​IMG]

    For that rebuild, you shouldn't need a new Eeprom, but it would definitely get you better performance if you had one burned for the engine specs.

    You can check for ECM codes very easily .... with a paperclip [​IMG]

    Check out <a target="_blank" href=http://www.sportmachines.com/maintenance/aldl.html>This Link</a> for the specific info.

    Basically, you jam a paperclip into ports A and B on the ALDL connector; then turn the key to the ON position (do not start it!)

    The check engine light will flash a code '12' 3 times to let you know it is in diagnostic mode. Code '12' will be a single flash, followed by 2 flashes. Then it will wait 3 or so seconds, and do it again. After the 3rd code '12' is flashed, any codes stored in the ECM will be flashed. When it is finished, it will do the code '12' 3 times again.

    I do this all the time in my '92 Camaro (TBI) for troubleshooting, and it works very well.

    Thomas.

    -- '84 1-Ton Blazer --
    When the goin' gets tough,
    the tough go 1-Ton [​IMG]
     
  14. ftn96

    ftn96 1/2 ton status

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    Yeah, thats what I was refering to when I said trip the puter.
    Sorry my sayings are probably only understandable to me. [​IMG]

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  15. CaptCrunch

    CaptCrunch 1/2 ton status

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    Does it only happen in the bottom of third? Is it better or worse if the vehicle is cold? Hot? If you are almost certin it is valves then it definely would be worth yanking the valve covers to have a look

    -Mikey
    1987 Chevy K5 Blazer- 350 TBI
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  16. ftn96

    ftn96 1/2 ton status

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    I've noticed it mostly when the motor is hot. And it happens when the motor is bogged down and Im giving it more gas to excellerate. Its not real bad. But I can hear it over the new tire roar. [​IMG]

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  17. ftn96

    ftn96 1/2 ton status

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    Oh one more thing I forgot about. When I was out wheelin one day I got stuck in some muck and after forward and reverse for like an hour I finally called my bud with the burban and he came and pulled me out. Then I shut the motor off and we had a beer or 2 shooting the breeze, then when I go to start it up to go home i had this loud knocking clank noise coming from the top of the motor. But it seems like as soon as the oil got back to the top of the motor it went away. The guy with the burb said it sounded like a colapsed rocker/spring or valve or something.
    So after about 4 months it hasn't done it any more, then one morning when I started it up, it did it for like 3 seconds then went away.
    Does any of this sound related?

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  18. ftn96

    ftn96 1/2 ton status

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    TTT, anyone else have some insight on this?

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  19. CaptCrunch

    CaptCrunch 1/2 ton status

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    It very well could be... I would pull the valve covers and inspect the springs and rockers... have a buddy crank it over w/ the coil disconnected and make sure oil is squirting up there... also if you can hear it cold maybe try and pin point which bank of cylinders or which cylinder.

    -Mikey
    1987 Chevy K5 Blazer- 350 TBI
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  20. ftn96

    ftn96 1/2 ton status

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    Alright cool. I need to replace the valve cover gaskets anyway. Im getting a leak thats trickling down to the exhaust collector.

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