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Knock sensor?

Discussion in 'The Garage' started by PsychoticDeadGuy, Oct 4, 2005.

  1. PsychoticDeadGuy

    PsychoticDeadGuy 1/2 ton status

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    I was wondering if my 87 K5 has a knock sensor or not. i want to change the cam and put in a gear drive...but how do i tell if there is a knock sensor or not?
     
  2. k20

    k20 3/4 ton status

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    if its an 87 it should have a knock sensor, IIRC, on the passenger side, either in the head, or the side of the block (cant really remember), I think in the head, about the place where the temp sensor is on the driver side. Should have a funny lookin hookup on it. A white round connector on the sensor, when the wire is unplugged.
     
  3. 1979jimmy350

    1979jimmy350 1/2 ton status

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    Do you have TBI if so you do have a knock sensor. If for some reason you have a carb look on your heads for a sensor in one of the waterjacket plugs that is round or look on the back of the heads. Most likley you do have one unless the system has been taken out
     
  4. PsychoticDeadGuy

    PsychoticDeadGuy 1/2 ton status

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    so can i take it out then? i want to run a gear drive but i dont want to make the sensor go crazy...
     
  5. k20

    k20 3/4 ton status

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    well the timing will never retard if you get ping. Prob wouldnt notice it till you put your truck in front of a load goin up a grade in the summer, then piston meltage may occur.
     
  6. PsychoticDeadGuy

    PsychoticDeadGuy 1/2 ton status

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    oh. ok then. i guess i will not mess with it then...what exactly does it do and how does it work?
     
  7. 1979jimmy350

    1979jimmy350 1/2 ton status

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    the computer advances your timing and when the knock sensor hears a small amount of knock it retards the timing a little to stop the knocking. It is a good system because you are getting the maxium amount of spark advance with out knock
     
  8. sweetk30

    sweetk30 professional hooker Premium Member

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    if pinging is detected in motor it works with the computer to retard timing.
     
  9. PsychoticDeadGuy

    PsychoticDeadGuy 1/2 ton status

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    ok, thanks guys. i appreciate it...
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    Head over to thirdgen.org and some of the LS1 sites. I know people have run the gear drives with no problem from the knock sensor. The knock sensor is SUPPOSED to be tuned to a specific frequency, (thus different between a 305 and a 350) BUT if they were so sensitive, one of the operational tests wouldn't be to hit the block with a hammer and watch the knock counts. :)
     
  11. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    [hijack]

    dyeager, do you think a solid lift cam will throw off the knock sensor because of the valve lash?

    [/hijack]
     
  12. Russ

    Russ 1/2 ton status

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    I have a knock sensor question also. Is it absolutely on every engine with TBI? Reason I ask is I have an 1988 454 engine that came out of a crewcab, and it does not have a knock sensor on it anywhere. I have the original wiring harness for the engine, and it does not appear to have a wire in it for a knock sensor.

    The 350 currently in my 1988 crewcab dually has a knock sensor in the block on passenger side, but that port was plugged on the 454. I am getting ready to transplant the 454 in my truck, along with the wiring harness and computer, but am concerned if the lack of a knock sensor is going to cause me problems. There was a sensor in each head for the 454, but the best I can determine is that one of them is a temperature sensor and the other is an auxilary fan switch. Neither one looks like the knock sensor on my 350.
    Thanks for any help,

    Russ
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    No idea on the solid cams. Never pay any attention to those threads.

    The 454's may not have used knock sensors, at least early on with TBI. IIRC, they were not present on all of the CCC (CA) truck setups either. The 305's had knock/ESC because of the high compression, but the 454's I'm assuming stayed low compression/conservative for our C/K/R/V series.
     
  14. JIM88K5

    JIM88K5 1/2 ton status

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    The knock sensor is mounted in the side side of the block, not the head.
     
  15. JIM88K5

    JIM88K5 1/2 ton status

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    Russ, I'll check see if the 7.4 uses a knock sensor and where it's located.
     
  16. Russ

    Russ 1/2 ton status

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    Thanks Jim! I know it does not have that ESC connector in the harness either like my 350 engine does.

    Russ
     
  17. JIM88K5

    JIM88K5 1/2 ton status

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    4.3/5.7/7.4 all show the same number knock sensor.

    Sould be above and slightly ahead of the starter.
     
  18. Russ

    Russ 1/2 ton status

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    Thanks Jim, my service manual I have is for a 90 model and it shows it there also, same place as the 350, but this 454 did not have one there when it came out of the donor truck, nor did it have a wire in the harness to attach to one. My truck and the donor truck were both 88's, so I am hoping that it was not required.

    Russ
     
  19. dyeager535

    dyeager535 1 ton status Premium Member

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    Very odd. Looks like the 305 was the only engine of that time that didn't use that number knock sensor. Well, that and whatever the V8 262 or whatever was that was available in the Caprices later on. Wonder what the difference was now.

    That goes against everything I've seen up to this point (knock sensors tuned to each displacement) but it's pretty hard to argue with the parts listings.
     

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