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.

My engine cylinder bore

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Stomp, May 22, 2002.

  1. Stomp

    Stomp 1/2 ton status

    Joined:
    Feb 23, 2002
    Posts:
    168
    Likes Received:
    0
    Location:
    Hill Air Force Base Utah
    OK, I mircometered my cylinders and here are the number's

    All 8 cylinders fall between 4.125 and 4.130. The stock bore is 4.125. Are the bigger bore's allowable for a daily driver or do I need to get it bored over???
     
  2. Thunder

    Thunder 3/4 ton status

    Joined:
    Jul 20, 2000
    Posts:
    8,946
    Likes Received:
    1
    Location:
    Northeast Nevada
    The bore on a 350 is 4.000
    I think the max alowable for a stock bore is 4.0025
    4.125 is a big hole for a stock bore.
    Is your engine already bored 10 over?
    look at the top of the pistons is there a 10 stamped on them?
    Did you also measure the bore taper? Should be no more than 0.005 diference between the top and bottom of the cylinder.
    You also need to check to see if the bore is out of round. Measure across the bore in several locations around the middle of the cylinder. max alowable difference is 0.002.

    If the bore does not meet any of these specs you need to get it bored out. if you dont have the proper micrometers or If un sure of what you are doing. take it to a machine shop and have them check it out.
    You can usually bore a block up to .060 over without problems
    In my opinion, its best to go ahead and have the block bored out another .010. that way everything is round and straight. The machine work and pistons dont cost that much more.You will end up with a much more durable and longer lasting engine that way.
     
  3. Stomp

    Stomp 1/2 ton status

    Joined:
    Feb 23, 2002
    Posts:
    168
    Likes Received:
    0
    Location:
    Hill Air Force Base Utah
    Sorry, I forgot to mention its a 396. The only micrometer I have will not fit inside the cylinder. I was measuring the top's

    Thx
    Stomp
     
  4. RedDwarf

    RedDwarf 1/2 ton status

    Joined:
    May 9, 2001
    Posts:
    816
    Likes Received:
    0
    Location:
    North Central Florida
    Hmm, 4.130 is on the outside of the tolerance.

    Factory spec is from 4.1246 to 4.1274

    And that is a 402, not a 396

    What is the casting number? maybe if it is a 396, it has already been bored .030"?
     
  5. Stomp

    Stomp 1/2 ton status

    Joined:
    Feb 23, 2002
    Posts:
    168
    Likes Received:
    0
    Location:
    Hill Air Force Base Utah
    I found some deep scratches on the walls so I'm just going to have it bored by a local machine shop. Thx for the help guys.
     

Share This Page