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Difference between 86 and 87 350 block? Need help

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 87superblaze, Mar 8, 2002.

  1. 87superblaze

    87superblaze 1/2 ton status

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    Here's my problem. I am going to rebuild my 87 TBI blazer because it smokes really bad. I suspect the heads are the problem but the block seems to be in good condition.

    No hears is were it gets confusing. I have an 86 3/4 ton 350 carb chevy w/ 57,000 original miles but it burns 1 quart a week! suspect rings. The valves are in good condition.

    I want to put the block from the 86 3/4 ton into my blazer and put the "good" 87 block into my 3/4 ton. This way I only have to rebuild 1 motor. The engine in the 3/4 ton would be good.

    Is there an advantage/ disadvantage to keeping the 87 block with the 87 blazer? Would you recommend I do this or should I just rebuild both engines?
    The 3/4 ton is mainly a work horse so it doesn't matter if the engine isn't perfect. What do you think?
     
  2. solowookie

    solowookie 1/2 ton status

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    I think the only real difference is the 1 piece rear main seal vs. 2 piece... I'm sure somebody will be along shortly to correct me if I'm wrong.
     
  3. RedDwarf

    RedDwarf 1/2 ton status

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    Well, because of that, the crank flange is different. You will need an 87-up flexplate or flywheel
     
  4. 87GMCJimmy

    87GMCJimmy 1/2 ton status

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    I'm not sure but there might not be all of the ports for the EFI sensors to hook into the 86 block. You need one for oil press for the fuel pump(separate from the dash gauge) and one for .... I forget it's down by the starter. It's not spark knock that's in the driver's side heads.....ops thinking out loud. Anyway these are somethings to look for.

    Mike
     
  5. ChevyCaGal

    ChevyCaGal 3/4 ton status

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    I have an 86 and mine is a the one piece seal... found that out when I had to replace the engine when I threw that lovely rod /forums/images/icons/mad.gif /forums/images/icons/tongue.gif
     
  6. solowookie

    solowookie 1/2 ton status

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    I took a 78 305 block out of my k5 (don't ask - that way when I got it), and it had the knock sensor etc. so that shouldn't be a problem
     
  7. CaptCrunch

    CaptCrunch 1/2 ton status

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    Shouldn't be a major hassle.. swap flywheels/flexpates and it should be ok. I believe some 86 blocks were 2 pc selas and some were one if I remember correctly.
     
  8. Blazer79

    Blazer79 1/2 ton status

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    I'm not positive, but I think 87 was the first year with roller lifters, which, in theory, should give you more power than hydraulic lifters.
     
  9. dragricinMT

    dragricinMT 1/2 ton status

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    The 87 should have center bolt valve covers,which means the heads on the 87 are different. The 2 center bolts on the intake on the 87 go in almost straight down. The 86 still has the old style heads that have the bolts going in at angle, which means different intake. Also the 1 piece rear main on the 87 compared to the 86 2 piece rear main.
    Hope this helps.
     
  10. RedDwarf

    RedDwarf 1/2 ton status

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    Now that I think of it, you're right.

    Thanks for screwing me up Jeff /forums/images/icons/tongue.gif
     
  11. solowookie

    solowookie 1/2 ton status

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    the head problem would only be a problem if you were using the TBI heads... block its self doesn't matter.
     

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