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Technical cam lobes problem

Discussion in 'The Hokey Ass Message Board' started by olscrounger, Jun 3, 2020.

  1. olscrounger
    Joined: Feb 23, 2008
    Posts: 3,849

    olscrounger
    ALLIANCE MEMBER

    Helping with a cam install on a Chevy small block. Fresh machine work etc. New cam bearings etc etc. Tried to put cam in and no go. Then tied a stock cam--no problem. Friend took back to machine shop.
    He tried the same--stock cam ok, after market NG. Lobes higher than bearing surface by .005 to .010 larger!! Never seen this before--returned cam and waiting for another. Anyone seen this before?
     
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 46,134

    squirrel
    Member

    that's a new one on me! Congrats.
     
    bobss396 and Deuced Up! like this.
  3. theboss20
    Joined: Dec 30, 2018
    Posts: 209

    theboss20

    Sounds like an old block...maybe even a 265 sbc...


    Sent from my iPad using Tapatalk
     
    bobss396 likes this.
  4. hummm Chinese cam?????
     
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  5. olscrounger
    Joined: Feb 23, 2008
    Posts: 3,849

    olscrounger
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    Yep Jim me too-I checked it too. Friends Uncle is doing most of assembly and he could not believe it either. He is an engine guru in his late 70's and has built Offys etc etc and still builds high end sprint car motors as well. Has done this for 50 +years. Summit is sending a new cam. It is a 70 350 that has been bored, decked, line honed etc etc by a high end machine shop.All was good til cam install.
     
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  6. Ericnova72
    Joined: May 1, 2007
    Posts: 376

    Ericnova72
    Member

    What does that have to do with anything....thyy all have the exact same size cam bearing bores in them. Every stock SBC block ever made has the same size cam bearing bores.

    The only difference in the very early 265 is that there is no oil annulus groove behind the bearings so it requires a cam with a groove cut in the rear bearing journal on the cam for proper oiling.

    Sounds like the cam grinder screwed up, lobe should never be higher than bearing journal diameter.
     
  7. Monday morning on the cam grinding machine.
     
  8. olscrounger
    Joined: Feb 23, 2008
    Posts: 3,849

    olscrounger
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    ^^^ No kidding!! Never seen such a thing.
     
    lothiandon1940 likes this.
  9. ^^^^^ Was it a custom grind?
     
  10. olscrounger
    Joined: Feb 23, 2008
    Posts: 3,849

    olscrounger
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    No custom grind Crane 266/440 have installed many--installed two last year in 327's
    mild cam--used to be the same specs from Cam Dynamics in the 80's
     
    lothiandon1940 likes this.
  11. Sounds more like 266/880 :eek:
     
  12. partssaloon
    Joined: Jan 28, 2009
    Posts: 424

    partssaloon
    Member

    I'll be interested to hear the outcome of this one!
     
  13. More than enough lift. Sounds like a bad set-up on the cam grinder. I spent 15 years with an aftermarket cam mfg who supplied OEM and the HP marketplace. Can't remember ever running across that particular problem.
     
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  14. I have put together quite a lot of SBCs.......never saw lobes that were bigger than the cam bearings......
     
  15. Add me to the “never seen that before” group


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  16. olscrounger
    Joined: Feb 23, 2008
    Posts: 3,849

    olscrounger
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    me either but it was that way. Talked to a custom cam grinder a bit ago and he said it is very rare but does happen. He has seen it before.
     
    lothiandon1940 likes this.
  17. CNC - Can't Knock-off Copy's
     

  18. I wonder how the cam could be installed with lobes outside the journal diameter.......some kind of voodoo? Two-piece bearings? Sounds like a data input mistake on the machine........right cam, wrong lobe profiles.....
     
  19. It's a set up error or a bad joke by a pissed off employ.
     
  20. LAROKE
    Joined: Sep 5, 2007
    Posts: 1,682

    LAROKE
    Member

  21. ^^^^^ They were Big Lobes!
    [​IMG]
     
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  22. Lloyd's paint & glass
    Joined: Nov 16, 2019
    Posts: 2,271

    Lloyd's paint & glass
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    Probably a dodge cam
     
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  23. Of a different era.
     
  24. gene-koning
    Joined: Oct 28, 2016
    Posts: 1,829

    gene-koning
    Member

    We bought a cam once where the bearing journals were larger diameter then the bearing inside diameter. Sent it back and they replaced the cam with one of the same part number, the second cam was good.
    Stuff happens and sometimes slips by the inspection point. Happens with everything from time to time. Get the replacement and move on. Gene
     
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  25. olscrounger
    Joined: Feb 23, 2008
    Posts: 3,849

    olscrounger
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    The replacement is already enroute.
     
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  26. Deuced Up!
    Joined: Feb 8, 2008
    Posts: 3,803

    Deuced Up!
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  27. alchemy
    Joined: Sep 27, 2002
    Posts: 15,520

    alchemy
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    I've read about a vintage engine that had a notch in the journal for a tall lobe to fit through. Can't remember where I saw it or the engine type though. Was probably really old and just a splasher system that didn't have pressured oil to a bearing. Some old engines ran the cam directly on the iron bore in the block.
     
  28. Blues4U
    Joined: Oct 1, 2015
    Posts: 4,681

    Blues4U
    Member
    from So Cal

    Cummins B series engines (the engines in OT Dodge pickups as well as a million other applications) have no cam bearings, the cam rides directly in the bore of the iron block. Bearing inserts are available for rebuilding engines, but they do not come with them originally (same thing with cylinder liners).
     
    Truckdoctor Andy likes this.
  29. Not to mention virtually every overhead cam application runs without bearing inserts


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    Blues4U likes this.

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