align bore and alignment of the crank

Discussion in 'The Bench' started by tlivingd, Jul 20, 2006.

  1. tlivingd

    tlivingd BIG BLOCK, THE ANTI PRIUS

    If you do an align hone/bore, does the crank center line move in relation to the block?
    if so how do you compensate with the seals and the crank connection to the trans. I have seen timing gear sets to compensate for the crank center line changing, but dosen't the output to the trans get thrown out of wack along with lining up the timing cover?

    If not, how do you pick bearings for the resize?
    ex1: Lets say the align bore took .010 off the block and left the crank alone, would you use a .010 OS bearing on the mains?

    ex2: If you took .010 off on the align bore and turned the crank mains down .010, would you need a .020 oversized bearing?

    I'm looking for some education.

    -nate
     
  2. Michael Evans

    Michael Evans a new project

    I am going to have a block honed my self one day as I have gotten a block the the main caps were missing and getting a new set.

    It would depend on why the crank needs to aligned honed as to where the crank center line may end up. Moving a crank 0.010" is extream. Most of the time (and if the mechinest knows what they are doing), it may only take 3 or 4 thousands off the caps or mains.

    The outer size of the bearing will be unchanged. It is the crank diameter that you may or may not have to reduce.
     
  3. Dale

    Dale Sweepspear

    My shop suggested I should have my block line honed because the caps fit rather tight in the block. :puzzled:
    Haven't yet.
    Not sure if I will.
     
  4. Michael Evans

    Michael Evans a new project

    The mechinest must be working on commission.................. :rolleyes:
     
  5. BUICK528

    BUICK528 Big Red

    change shops, run, don't walk....

    JH
     
    1973gs likes this.
  6. DaWildcat

    DaWildcat Platinum Level Contributor

    The caps should fit tightly in the block, this is called cap registration. In some cases a heavy plastic mallet may be required to get the caps to seat properly before torquing the fasteners. It's when the caps don't fit tightly that you've got trouble. The block, not the fasteners, must locate the cap position.

    Align honing can change the centerline of the crank, bringing it closer to the cam if enough material is removed. This is because the equipment usually self-centers between the caps & block.

    Align Boring if done properly will preserve the original cam-to-crank spacing. The equipment can be set up to remove the majority of material from the cap side.

    Of course, either way the job is only as good as the equipment & the person doing it!

    Devon
     
  7. Dale

    Dale Sweepspear

    You just confirmed my beliefs!

    Yeah! Every engine I have worked on, the caps had that snug fit!
    I gave the guy a funny look when he told me that! And just said "yeah, maybe later".
    He told me this when I was picking up the block after having it bored & honed.
    Reputable shop, been in business since 1957.
    I think they thought they could pick my pockets more. :moonu:
     
  8. doc

    doc Well-Known Member

    align boreing

    Nate, You are a trouble maker, You actually THINK. Good for you, we need more of em. :laugh:
    I have never seen a block that was aligne bored that didnt move the crank closer to the cam and that produces slack in the timing chain. With that comes spark scatter. not good. I never do that unless there is absolutely no other choice. :Brow:
    I like to deck a block parallel to the center line of the crank, then bore it. then the deck heights are the same and the bores are 90 deg. to the center line of the crank. This makes more power and lives longer. :Smarty:
    You will find that machine shops have people working in them that think they are the only ones who can figgure out what is going on inside an engine. Find a shop that is willing to work with you as they take your money.
    that is a novel idea, The customer is in controll!!!!!! and knows what is going on. :bglasses:
    Hang in there.
     
  9. DaWildcat

    DaWildcat Platinum Level Contributor

    My preferred order for the steps in block machining & why:

    #1 - Align bore the block, keep crank-to-cam centerline as stock to avoid timing chain slack. A final, very light align-hone may be necessary for the best results. The main bore will be the datum, or baseline for the next steps.

    #2 - Deck the block in relation to the new main bore centerline. Distance from all four corners of the deck to the crank centerline will be the same, and square. Finish is determined by the head gasket used.

    #3 - Bore the cylinders in relation to the fresh deck, 90 to the crank centerline, with cyl bore centerline spacing corrected as well. Finish hone to piston ring manufacturer's recommendation, set piston-to-wall clearance on every piston.

    Some people go crazy for competition, corecting the camshaft centerline and lifter bores, squaring bellhousing surface, even offset doweling to correct crank-to-input shaft alignment as well. I've never had a serious need to do those extras, but it's been done!

    Devon
     
    Last edited: Jul 22, 2006
  10. DaWildcat

    DaWildcat Platinum Level Contributor

    Sorry Nate, I forgot to answer your questions:

    Before the hone/bore job is performed, a small amount of material is removed from each side of the main caps where they meet the block. When bolted to the block, this results in a bore that is no longer round.

    The hone/bore job is then performed, returning the bore to a round, nominal diameter as the factory intended. By doing the work this way you will not need undersize bearings unless your crank has been turned. In other words, if you were running std bearings before, you can run them again. Main bearing undersizes are to accomodate crank diameter only.

    Depending on the amount of material removed, I'd expect the rear seal groove to need some attention after boring/honing as well.

    Devon
     
  11. mktup

    mktup Member

    Maybe you misunderstood your machinist, or he didn't explain himself well enough. He might have been referring to the main bearing bore being tighter than the low end of the spec. giving you more bearing crush than desireable. This will give you a tighter bearing clearance and pinching in of the bearing insert at the parting line severly limiting the oil supply. Not good.
    At my shop this is the first operation we do in front of the customer when the block is bought in. Check for register, torque mains to spec. set dial bore gage and show the customer whats going on. If the register is loose we have to peen it then line hone. We explain to the customer the importance of having main bearing bores round, within spec and no taper. Invariably, a block with 80 or 100K on the clock will need the proceedure. Now, if the customer does not want it done because of $, we politely tell him to take his stuff to another shop as we will not work on it if not done properly. A spun main is no fun, when you could have avoided this pain for 150 bucks. So, when we see the same fellow come back in three months we never say told ya so.

    Lyman
     
  12. faster

    faster Well-Known Member

    align it

    Good advice Lyman. I use an excellent machinist (he has done the machine work on five motors for me and is expensive) but I have never had one of my motors come apart. They are all sewing machine smooth and the one in my TR 11.23@121 MPH is 8 years old and never been out of the car yet. It does not leak or burn oil has about 12K miles and 100+ passes on it. I'll pay for that peace of mind.

    Mikey
     
  13. Jim Weise

    Jim Weise EFI/DIS 482

    Aline hone or Bore will reduced the distance from the crank to the cam certerline.

    Honing less than boring, but they both will move it.

    This is because in both proceedures, the caps are milled on the bottom, to make the hole smaller when they are bolted back on the block. In the case of honing, just a few thousands, maybe twice as much when it's going to be bored. And in the align bore process, it's brought to finished size with the hone, after they rough cut it with the boring bar.

    We align hone all normal rebuilds, and align bore anything that gets a block gridle.

    Get a .006 short rollmaster for an align honed motor, a .010 shorter one for an align Bored motor. TA carries both in stock.

    In an align hone situation, if very little material has to be removed, I have had experience building resto motors, that will take the stock timing chain just fine, and that is all that is required if your building a light valvespring pressure/small cam stocker. The billet timing set is a bit of overkill, as long as the cam will degree properly with the stock replacement chain.

    You will have no other problems, neither the crank centerline/convertor location nor the timing cover seal locations are that precise. They can handle moving a few thousanths.

    Failure to get the main housings round in a rebuild is the number one cause of rod bearing failure in the 455, no question about that, I have fixed many motors build elsewhere for exactly this reason. Run from anyone that tells you otherwise.

    JW

    PS.. Dale.. "Caps too tight".. that's funny. Never seen one with too much register.. seen a few with not enough..

    Give me a call, I will give you the names of the two shops here in town that can do the shortblock machining properly.
     
  14. freak6264

    freak6264 Myotonic when confronted

    I'm needing help with this. I know my block was line bored. my question is this- a new timing chain/gear set has slack on the follow up side- there is about 3/8 to half an inch play in the chain (at the midpoint)- and this is a new set- so my question is this- with that small amount of information- does anyone have any idea which timing set I need from T/A? Talked to them today and they said there was no real way to measure how much was changed- I really don't want to do the trial and error thing. I could triangulate off the centerlines, but I don't have calipers large enough to be accurate...help!!:Do No:
     
  15. Bigpig455

    Bigpig455 Fastest of the slow....

    I know this is an old thread, but does anyone have the correct crank/cam centerline distance spec for a BBB?
     
    1969RIVI likes this.

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