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Technical How to align bellhousing on a sbc

Discussion in 'The Hokey Ass Message Board' started by sdluck, Oct 3, 2019.

  1. sdluck
    Joined: Sep 19, 2006
    Posts: 3,186

    sdluck
    Member

    I bought some offset dowels but cant get them clocked ,left side can not knock out.they are .621 and threaded new ones are not threaded SBC aluminum block
     
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  2. saltflats
    Joined: Aug 14, 2007
    Posts: 12,594

    saltflats
    Member
    from Missouri

    Drill and thread the dowel, then use a bolt or a stud and some spacers to pull it out.
     
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  3. Mr48chev
    Joined: Dec 28, 2007
    Posts: 33,861

    Mr48chev
    ALLIANCE MEMBER

    Aluminum block not drilled all the way though like an iron block so you can use a punch and drive them out from the back?
     
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  4. sdluck
    Joined: Sep 19, 2006
    Posts: 3,186

    sdluck
    Member

    The new ones are not tapped.The adj ones are not available here in san jose ca.

    Sent from my SM-J737T using The H.A.M.B. mobile app
     
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  5. DDDenny
    Joined: Feb 6, 2015
    Posts: 19,143

    DDDenny
    Member
    from oregon

    SD
    Curious, how far out is it without offset dowels?
     
  6. sdluck
    Joined: Sep 19, 2006
    Posts: 3,186

    sdluck
    Member

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  7. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 4,217

    ekimneirbo

    If its an aluminum block I would be very careful about removing it. You might try a little heat from a propane torch in case they have lock tite on them. Propane CAN melt aluminum......don't ask. If you can't get it out I would try drilling it very carefully. Centerpunch it as close as possible. If you have access to a lathe, you can make a slip on bushing with a solid end. While in the lathe, center drill and then drill a small hole thru the end of the plug. Then slip the plug on the dowel and use it as a guide to centerdrill the dowel. Then keep drilling larger sizes till there is almost no pin left in the hole. Then carefully try to punch the remaining pin loose and extract it. I would be very careful about pressing out a pin in an aluminum engine.
     
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  8. dreracecar
    Joined: Aug 27, 2009
    Posts: 3,476

    dreracecar
    Member
    from so-cal

    I am also interested on why you need offset dowels, those are usually for blocks that have had major repair and line-bored so much that the crank was raised in the block
     
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  9. I think he is saying the ones in the aluminum block are threaded .
    And the new ones are not?
    Unless I misread his post?

    It should be accurate already,,,unless you are using a blow proof bell housing ?

    Tommy
     
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  10. sdluck
    Joined: Sep 19, 2006
    Posts: 3,186

    sdluck
    Member

    That is correct
     
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  11. sdluck
    Joined: Sep 19, 2006
    Posts: 3,186

    sdluck
    Member

    Block was alignbored
     
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  12. Mimilan
    Joined: Jun 13, 2019
    Posts: 1,230

    Mimilan
    Member

    Use a dial test to get it aligned. Then drill the bell/block and use roll-pins .
     
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  13. sdluck
    Joined: Sep 19, 2006
    Posts: 3,186

    sdluck
    Member

    I know how to check it,I can't get adj pins.I was looking for a way to do it without them.
     
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  14. s55mercury66
    Joined: Jul 6, 2009
    Posts: 4,335

    s55mercury66
    Member
    from SW Wyoming

    I like that idea, thanks for that.
     
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  15. buffaloracer
    Joined: Aug 22, 2004
    Posts: 816

    buffaloracer
    Member
    from kansas

    Find a retired machinist that likes to tinker at home and have him make you a pair. That would work in my neighbor hood. Don't know about yours.
    Pete
     
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  16. 53 hemi
    Joined: Jan 8, 2009
    Posts: 501

    53 hemi
    Member

    I'll just throw my thoughts in here real quick - it sounds like it is what it is; ya gotta get that dowel pin out. I think I'd very, very carefully attempt to drill it out.

    Having the block holes threaded is a bit of an issue, as well. I've included a link to the offset dowels that I use. They are available in slightly different widths - its possible that you could drill the threads out of the original holes and fit these in without having to over drill and sleeve the original holes.

    None of this is going to be fun, but you're only going to have to do it once. Good luck.

    https://www.robbmcperformance.com/products/dowels.html

    Sent from my SM-G950U using The H.A.M.B. mobile app
     
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  17. dreracecar
    Joined: Aug 27, 2009
    Posts: 3,476

    dreracecar
    Member
    from so-cal

    First thing people need to understand that the Chevy dowel pin dia is .620 and NOT .625. I had to have a special reamer made to do motorplates for the racecars I build. There is an accepted tolerance on mis-alignment, but if your block was machined enough to warrant the offset dowels then you will have issues with the timing chain and will have to go with a gear drive. The only alu blocks I have ever come across that have screw in dowels are the alu 426 hemi style race blocks and those are .500". Peronally, I would open the holes in the steel bellhousing (this might include the attachment bolts also), line it up and then spot weld a .621" ID ring to the flange. and don't mess with the block
     
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  18. dirty old man
    Joined: Feb 2, 2008
    Posts: 8,910

    dirty old man
    Member Emeritus

    As a retired machinist of 50+years experience, I agree with dreracecar in post #17 above. Start fooling around with a hand held drill, attempting to eliminate the threads in the backside of the block would most likely result in a first class mess, possibly meaning removal and tear down of engine so as to be able to get it on a mill table and bore/sleeve/relocate the dowelpin holes. As stated you may have to slightly open the holes where the bell housing bolts go.
     
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  19. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    I'm not quite sure what yo0u are saying here. But they do make pullers for drive in dowels. They work great. If you want to drag that block to San Mateo you can use mine.
     
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  20. DDDenny
    Joined: Feb 6, 2015
    Posts: 19,143

    DDDenny
    Member
    from oregon

    SD
    Not sure what you got going on with your block but my Rodeck has .620 dia. press-in dowels that are drilled and tapped.
    I don't recall what trans/belhousing you're using but I have seen what Bruce suggested done many times on manual trans scattershields.
    My Lakewood has the clutch bracket adjacent to the dowel so a little creativity would be required when welding the new alignment "heavy washer" in that area but it's very doable, the other side is wide open for access.
     
    Last edited: Oct 5, 2019
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  21. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 4,217

    ekimneirbo

    Lets start over, because I think there is some confusion about what you are saying. There are at several kinds of dowel pins.
    1. Apparently there are dowel pins which are threaded and screw into the block itself.
    2. Then there are dowel pins which press into the block and have a threaded section which lets you rotate an eccentric
    bushing and lock it in place with a set screw.
    3. Next are press in bushings which have different centerlines on each end.
    My understanding is you have dowel pins that screw into the block and are concentric the whole length. Is that a correct statement ? If so, you definitely don't want to attempt to press them out. Slight heat may break them free and allow you to turn them out. If not, refer to my drilling suggestion above.
    Does the manufacturer of the block have any suggestion as to how to remove the pins ? Surely you are not the first owner of one of their blocks who has had a need to realign a bell housing after align boring. Maybe they have a screw in pin that has an eccentric. Is Rodeck still in business?
     
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  22. sdluck
    Joined: Sep 19, 2006
    Posts: 3,186

    sdluck
    Member

    The block has been line bored,I have a scattershield I have removed the dowels they are .621 in dia,long for a motor plate and threaded.I removed them because The scatter shield did not index and is offset.I am having a hard time getting offset dowels.I ordered a set today.
     
  23. sdluck
    Joined: Sep 19, 2006
    Posts: 3,186

    sdluck
    Member

    thanks for the offer.
     
  24. dirty old man
    Joined: Feb 2, 2008
    Posts: 8,910

    dirty old man
    Member Emeritus

    I still don't understand just where these threads come into the assembly, unless you mean the dowels are screwed into the back of the block in drilled and tapped holes. If this is what you're saying then you can't use an offset dowel unless you have a lock, or jam nut to secure the dowel where you have it clocked for the offset.
    If the dowels are threaded and screwed into the block, the method in post # 17 is the easiest, and most practical way to do the job.
     
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  25. dreracecar
    Joined: Aug 27, 2009
    Posts: 3,476

    dreracecar
    Member
    from so-cal

    Rodeck is no longer making engine blocks
     
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  26. saltflats
    Joined: Aug 14, 2007
    Posts: 12,594

    saltflats
    Member
    from Missouri

    I need to see a picture now. o_O
     
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  27. DDDenny
    Joined: Feb 6, 2015
    Posts: 19,143

    DDDenny
    Member
    from oregon

    Here's two. 20191005_161439.jpg 20191005_161727.jpg
     
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  28. saltflats
    Joined: Aug 14, 2007
    Posts: 12,594

    saltflats
    Member
    from Missouri

    Okay, so the dowl is threaded in the center, and he is looking for offset dowels that are threaded in the center. I got it now. :confused: :)
     
  29. Good looking Rodeck,

    So,,,the dowels are not screwed in,,,but are threaded in the center to be pulled with a slide hammer?
    In the tool and die trade,,,,that is called a pull dowel.

    Tommy
     
  30. King ford
    Joined: Mar 18, 2013
    Posts: 1,477

    King ford
    Member
    from 08302

    Pictures or it didn't happen!!..in my EARLY twenties ( a few moons ago now!) I made my own offset dowels by brazing and file'ing.....yes, I was CHEAP !...had more time than money!
     

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