Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

TBI timing (backfire)

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by lowlevell, Aug 25, 2000.

  1. lowlevell

    lowlevell 1/2 ton status

    Joined:
    Jun 27, 2000
    Posts:
    343
    Likes Received:
    0
    Location:
    Central Ohio, USA
    Last night driving home my sub backfired through the carb.Today after looking into it,i noticed the timeing was retarded 6-8 degrees.When i bought the truck last year it was retarded 6-8 degrees.My question is,why is the timing jumping so far out?


    My engine (sb350 TBI) has 176,000 miles on it,with a factory oil cooler.And the engine doesnt smoke/knock/tick.The engine also seems very tight still.I've never had a vehicle's timing go that far out in a year.Has anyone else had this problem?

    And yes i disconnected the "spout connector" before i set the timing =)
    Later...
     
  2. 87Blzr

    87Blzr 1/2 ton status

    Joined:
    May 24, 2000
    Posts:
    111
    Likes Received:
    0
    I have the same exact engine with exactly the same mileage as you but haven't had that problem yet. Even though the distributor hold down bolt is tight check to see if you can turn the distributor anyway. Thats alot of degrees to go out so I don't think the timing chain would be stretching anywhere near that. Tough call. I would imagine it would be something with the distributor. Pull the cap and check the play the rotor has. Something has to be loosening somewhere

    87 K5 Siverado, 68 SS 396 Camaro
     
  3. DMK

    DMK 1/2 ton status

    Joined:
    Feb 20, 2000
    Posts:
    757
    Likes Received:
    0
    Location:
    CINCINNATI, OH
    Had this problem with my 89. Distributor hold down bolt kept coming lose. Use some loc-tite on it should be fine.
     
  4. K5 NUTT

    K5 NUTT 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    1,611
    Likes Received:
    0
    Location:
    Grand Junction Colorado
    If everything else checks out fine my guess would be what most don't consider....timing chains do strech with age...allowing the sprocket teeth on either the cam gear or crank gear to jump a tooth or so...

    AZBlazer

    1979 K5
    1976 K5 Chalet
    1972 K10 Suburban
     
  5. 87Blzr

    87Blzr 1/2 ton status

    Joined:
    May 24, 2000
    Posts:
    111
    Likes Received:
    0
    You could always check the timing chain slop easy enough. Put a breaker bar on the harmonic balancer bolt and turn the crank back and forth until you feel resistance. Its easy to turn over the engine without turning the cam because you don't have to overcome the valve spring pressure. Sometimes you have to loosen up some of the accessory belts to get a good feel but it works. You could even put the timing mark on top dead center then do it to see how many degrees of slop you have.

    87 K5 Siverado, 68 SS 396 Camaro
     
  6. sosamantx

    sosamantx 1/2 ton status

    Joined:
    Aug 14, 2000
    Posts:
    393
    Likes Received:
    0
    Location:
    somewhere in Texas
    My dad had paid someone to put an old motor of his in my Chevelle, and one of the many problems that I ran across, was that they put a bolt in the distributor hold down that was too long. I kept wondering why my timing was changing like that. This had gone on several times and finally I grabbed the distributor and it turned. The distributor didn't turn easy, as I had to put a little effort to turn it, that's when I pulled the bolt and noticed it. - Steve

    Steve Sosa a.k.a. "sosaman"
    http://sosaman.home.texas.net/carpics.html
     
  7. lowlevell

    lowlevell 1/2 ton status

    Joined:
    Jun 27, 2000
    Posts:
    343
    Likes Received:
    0
    Location:
    Central Ohio, USA
    It has been a couple days since i reset my timing and everything seems fine.The first thing i checked was to see if the dist. was loose,it wasnt.I havent checked for slop in the chain yet.I've had a chain jump on me in another vehicle,it used to backfire through the carb and burn while it ran=).This isnt the case this time.It just seems weird that it has moved that much in just over a year.BTW, in no way do i baby this truck=).....later
     

Share This Page