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Lifter noise? Tick tick tick...

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by newyorkin, Jul 5, 2002.

  1. newyorkin

    newyorkin 1 ton status

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    Hey all,

    For a couple months now, I've had this tap tap noise come and go. At first, I could swear it was a lifter, even lined up and started a motor swap. Halfway through the motor swap, at the point where everything was disconnected and the hoist was holding the motor up, I backed out 'cause the new motor wasn't what I thought it was. I put everything back together, and added some gaskets to the center and rear drivers side exhaust manifold ports. When I fired it back up and gave it some good hard driving, the sound was gone, and stayed away for a couple months. I had everything disconnected then reconnected, so I can't even pinpoint by what exactly I changed, just beefing up the exhaust seal.

    In the last month or so, it's come back with a vengeance. At first real spotty, here and there, and only in realllly hot conditions. In the last 3 weeks it's become full time. I added some motor honey, then some of that stuff they say is supposed to clean and quiet lifters, and now the sound is gone on first startup of the day, but comes back with every other startup or hard driving.

    Exhaust manifolds are super-tight, anymore and the bolt heads will come off...
    I tried listening to different parts of the motor with a tube to my ear, but can't seem to find it. I can't tell what part of the motor this sound is even coming from anymore.

    I would happily ignore it, but it's robbing power. Enough so that with the AC on, I have to floor it to keep pace up highway hills. Even with the AC off I have to give it too much juice to go. When the sound is not there, the truck feels like a stump puller (ok, maybe a little less, but feels like night and day with this noise).

    Any help is greatly appreciated!!!
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    The only way I can tell the difference between an exhaust leak at the head and a bad lifter is that the exhaust leak is most pronounced under load. The bad lifter will tick no matter the throttle input. A cracked manifold would have a steadily worse leak as the motor warms up (and the crack expands due to heat) If this is the case it may be giving the O2 sensor a false reading and the computer could be compensating causing your power loss.

    Rene
     
  3. newyorkin

    newyorkin 1 ton status

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    Tanks Rene. I actually have been getting an O2 code every so often lately. It's real wierd. I really think it's exhaust because of the way it acts, but then I think it's not because it's so incredibly quiet ad strong when it's not tapping... Tapped and ticked all day today in 6 hours of driving, then at one point taking off from a light backfired and lurched. VERY unusual for the truck to act like that at all. Even with this problem it's been a very smooth runner.
     
  4. reddog64

    reddog64 1/2 ton status

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    hehe... last tiem i heard that noise my BBC 468 was toast...

    Did i mention it DIED..

    your is probably exhaust...

    listen closely at low idle...
     
  5. 70~K5

    70~K5 1/2 ton status

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    Have someone hold a rag in the exhaust pipe with the motor running and you should be able to tell where it's leaking at.
     
  6. 4x4k20

    4x4k20 1/2 ton status

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    take the hose and hold it to the fuel pump i had a tick on my 80 gmc that i thought was a lifter turned out to be the friging fruel pump just a suggestion that might help.uh oh sorry i just saw that you have a fuel injected truck my brother has a 94 z71 it will go to ticking if he doesnt run 5w 30 motor oil in it explain that ?
     
  7. newyorkin

    newyorkin 1 ton status

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    That almost makes sense. When I tried to run 10w in my Camaro, I got some pretty inconsistent and wierd oil pressure, and all the lifters were making noise. I think it's something with the clearances that 10w won't flow as well through.

    I drove the truck around for a couple hours today with the AC cranked all the time, and it was on and off. She's sucking gas without haulin' ass though, I'm probably down to 8mpg...
     
  8. clayoval

    clayoval Registered Member

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    Well lets see fuel injected ticking loss of power loss of mpg you got a injector that has gone south it is a common problem for a injector spring to go out couse a pulse and a tick or knock that sounds like a lifter or even a rod bearing. Keep in mind that this was alwise a problem on alison engines and I have no idea how your injection works but I betting it is a injector that is sticking and or failed get a new set of nozzles and it should go away with a great gain in power and mpg
     
  9. newyorkin

    newyorkin 1 ton status

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    cool, thanks for the idea. Would that follow engine RPM, though? I have a TB from a later Caprice 350 (not sure what year), anyone know if the injectors are the same? The TB itself looks identical except for an extra vaccuum port or two and a different TPS.

    We bought my wife a new car yesterday, so I'm going to take hers as my DD, then park and disassemble the K5...
     

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