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line boring

Discussion in 'The Hokey Ass Message Board' started by Road Kill PU, Nov 4, 2012.

  1. Thinking about doing a rebuild on my 235 or a 261 inline 6 Chevy. I had talked to one of the guys that is good on these old engines and he said I should have a line bore job done.:confused: Is this enough better than just a standard bore job to justify the added expence? This car will be driven a lot so I want it to be done right. Thanks for your input.
    Later,
    Dick
     
  2. Vandy
    Joined: Nov 15, 2009
    Posts: 368

    Vandy
    Member
    from L.A. Ca

    I think you are confused
    Line bore is for the mains not the pistons
     
  3. Line bore would be for the mains unless their is some thing wrong you should not need to do a line bore take that block to a good machine shop and they will make sure every thing is good.
     
  4. I understood what a line bore was, but questioned if doing a line bore would benefit me on the engine rebuild. Thanks for the responce.
    Later,
    Dick
     
  5. BOBCRMAN
    Joined: Nov 10, 2005
    Posts: 846

    BOBCRMAN
    Member
    from Holly

    Unless the engine has experienced an overheated or spun main bearing in its past. You should not require a line bore for a stock rebuild. These engines are not known for that type of problem.

    It will require hardened exhaust seats for a "working" engine. A "parade" engine can get by with a standard valve job and some lead additive.
     
  6. He is talking aboput getting your main bearing saddles in a perfect line. It will free up a little torque if it is done right and they were not already in alignment.
     
  7. E.C.
    Joined: Apr 7, 2007
    Posts: 612

    E.C.
    Member
    from Tx

    why not.
     
    Last edited: Nov 6, 2012
  8. RPM
    Joined: Feb 5, 2005
    Posts: 204

    RPM
    Member

    I would not build an engine with out having it align honed. Cheap insurance on main bearing life.
     
  9. tig master
    Joined: Apr 9, 2009
    Posts: 416

    tig master
    Member
    from up north

    Have it measured at a good shop it is either a go or no go after measurement.

    T
     
  10. 52HardTop
    Joined: Jun 21, 2007
    Posts: 1,103

    52HardTop
    Member

    I say do it. When assembling my 54 235 after machining the crank wouldn't spin. I had to return it for a line bore. All was fine after that.
    Dom
     
  11. Thanks again for your advice. The hardened valve seats are a must as this car is going to be driven.
    Later,
    Dick
     
  12. MeanGene427
    Joined: Dec 15, 2010
    Posts: 2,307

    MeanGene427
    Member
    from Napa

    Best advice so far. An align hone is sometimes called for- let the machine shop check it first. If the main bores are not square with each other (in alignment) or are improperly sized for proper bearing crush, a properly-done align hone will correct it. Downside, and why I don't have it done unless necessary, is it moves the crank slightly closer to the cam, with timing chain slack or tighter clearance if it has timing gears. Not something you want to just say yes or no, check it first, don't let them just check it off on the work order to jack the price up
     
  13. greg32
    Joined: Jun 21, 2007
    Posts: 2,265

    greg32
    Member
    from Indiana

    Good advise, with a six I think you have a gear driven cam, and if your shops a little off, align bore will mess up centers. As said, check it, maybe hone, but try not to bore it. Also, try not to take too much off the deck of block, and head surface. Just enough to clean them up. Do pay for a balance, big difference,
     
  14. sunbeam
    Joined: Oct 22, 2010
    Posts: 6,384

    sunbeam
    Member

    This is an if you need it thing like surfaceing a head. I like boring better honing. Boring done right will not move the center line of the crank much while a hone will move the center line closer to the cam.
     
  15. There are 2 ways to save money when building an engine, "half fast" and "half assed".

    Building an engine "half fast" will save you money because it won't cost you an arm and a leg for all those fancy speed parts but won't cost you money in the long run because it was built right.

    Building an engine "half assed" is a recipe for disaster that will cost you in the long run.

    Don't be pennies wise and dollars foolish. Align boring doesn't cost that much. Just get it done!
     
  16. CNC-Dude
    Joined: Nov 23, 2007
    Posts: 1,043

    CNC-Dude
    Member

    These engines cannot be align honed, only line bored, since all 4 of the mains housing bores are about .100 larger than the next one in line. GMC's are the same, 4 different size main housing bores.
     
  17. If you have a 261 for example, here are the specs and why it can't be align honed.

    #1 2.6835-2.6845
    #2 2.7145-2.7155
    #3 2.7455-2.7465
    #4 2.7765-2.7775
     

  18. Did NOT know that- they also did that on the early Chevrolet 4 (1928 and prior) and it's ANNOYING at best!!!
     
  19. Pete1
    Joined: Aug 23, 2004
    Posts: 2,262

    Pete1
    Member
    from Wa.

    ANY method other than sleeving the saddles will move the centerline up.
    The ammount depends on how much you have to take off the caps to get it to clean.
    Like others here have said, you can't hone these engines because of the different diameters of each bore.
    They could be checked with a stepped test bar but my guess is there aren't many of those left around any more.
     
  20. oj
    Joined: Jul 27, 2008
    Posts: 6,575

    oj
    Member

    How many miles you got on that old motor? More than a 100K? Maybe it has already been rebuilt before? Don't you think that the mains are already in line? Like maybe there is a real good reason why that engine is 60 years old and still running?
    Let the machine shop true up the mains on some toyotas but leave yours alone.
     
  21. Heres what I have on the discussion of the " Shim Pack ". Now what I have is that this applies to the 54-55 w/ Dowel Pin type main bearings - UNDER NORMAL CONDITIONS.
    This would not apply to the 56-62 engines.

    " Under normal conditions Main Bearings should be assembled with a .004" shim pack on each side between the caps and the block. This should not extend between the bearing parting line surface. Remove shims to give a slight drage, then add 1 of a - .002" shim per side ".
     
  22. sunbeam
    Joined: Oct 22, 2010
    Posts: 6,384

    sunbeam
    Member

    On most engines you can set the bar that It just touches the top of the crank bore and most of the metal will be removed from the cap. With a hone an equal amount will be removed top and bottom.
     
  23. Dan Timberlake
    Joined: Apr 28, 2010
    Posts: 1,576

    Dan Timberlake
    Member

    More than one source has said if a straight (measured) crank turns freely in bearings with correct clearance the main line is straight enough. Makes sense to me.

    The bores (without inserts) do need to be qualified regarding size, roundess and taper.
     
  24. Candy-Man
    Joined: Mar 21, 2006
    Posts: 1,715

    Candy-Man
    Member

    I run a GMC Jimmy 302 in my Belly Tanker and the mains are all different sizes. My opinion, DO NOT align bore ! What are you going to do for main bearings ? Some people have advised to align bore, sure, if you can purchase bearings !

    You better talk with your machinist and discuss this issue regarding different size main bearings first !
     
  25. Curt B
    Joined: Oct 15, 2009
    Posts: 325

    Curt B
    Member

    A CMM will make quick work of determining EXACTLY how concentric the main bores are and shouldn't the amount of misalignment be determined before getting out the boring bar? Amazing what is done to make up for a lack of measurement capability.
     

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  26. CNC-Dude
    Joined: Nov 23, 2007
    Posts: 1,043

    CNC-Dude
    Member

    When you line bore or align hone a block the main bearings are not affected at all, you can use any main bearing just the same as if you didn't line bore or align hone the block. During this process, the housing bores are restored to their factory specs by cutting a few thousandths off of the caps mating surfaces to close the housing bores up so they can be resized just like reconditioning a set of rods. You must be thinking of a VW where the housing bores are actually made larger than they were originally and special OD bearings are required.
     
  27. Pete1
    Joined: Aug 23, 2004
    Posts: 2,262

    Pete1
    Member
    from Wa.

    That isn't how a rigid hone works.
     
  28. saltflats
    Joined: Aug 14, 2007
    Posts: 13,248

    saltflats
    Member
    from Missouri

    If it was line bored what would you do for cam gear play if the crank moves any up down or sideways . JMO if it was in need of line boring Iwould look for another block.
     
  29. Pete1
    Joined: Aug 23, 2004
    Posts: 2,262

    Pete1
    Member
    from Wa.

    There are oversize gears available for both gear and chain applications.
     
  30. Candy-Man
    Joined: Mar 21, 2006
    Posts: 1,715

    Candy-Man
    Member

    Quote:
    Originally Posted by Candy-Man
    I run a GMC Jimmy 302 in my Belly Tanker and the mains are all different sizes. My opinion, DO NOT align bore ! What are you going to do for main bearings ? Some people have advised to align bore, sure, if you can purchase bearings !

    You better talk with your machinist and discuss this issue regarding different size main bearings first !

    Quote CNC - Dude : When you line bore or align hone a block the main bearings are not affected at all, you can use any main bearing just the same as if you didn't line bore or align hone the block. During this process, the housing bores are restored to their factory specs by cutting a few thousandths off of the caps mating surfaces to close the housing bores up so they can be resized just like reconditioning a set of rods. You must be thinking of a VW where the housing bores are actually made larger than they were originally and special OD bearings are required.

    Sorry my response should have said "line hone" and not "line bore". However; how would you ever line hone a Jimmy block as the main are different sizes, what would you use to center ? I still maintain, I would not venture into either territory if you did not believe there was an issue, ie: spun bearing.....

    I must have really messed up my Jimmy block in my Bonneville car ! :) :)
     

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