401 camshaft

Discussion in ''Da Nailhead' started by john m, May 5, 2019.

  1. john m

    john m Well-Known Member

    Need help have 1966 skylark 401 engine have to set timing to like 20 degrees advanced to run dont know what cam is in it real rough and lumpy idle smell unburnt fuel when idling carb and ignition good does anyone know who sells stock cam?
  2. Bigpig455

    Bigpig455 Fastest of the slow....

    TA Performance, Carmen Faso or Camcraft Cams ought to be able to help you out. But before you take it apart, are you sure everything else is cool? Distributor, carb and vacuum?
  3. GranSportSedan

    GranSportSedan Puppet dictator, wife has all power

    When I called Carmen about a camshaft he mentioned that he wasn't able to provide them right now because he was having issues getting blanks
    Last edited: Aug 25, 2019
  4. gsgtx

    gsgtx Silver Level contributor

    did u unplug the vacuum advance when you time it
  5. john m

    john m Well-Known Member

    distributor good coil good called Carmen good info great guy possibly bad grind on cam will see
    GranSportSedan likes this.
  6. jmos4

    jmos4 Well-Known Member


    Could it be a tooth off, I had a similar issues on a Olds 330, also make sure the breaker plate/vacuum advance and weights aren't hanging up.

    Good luck, regards,
  7. wkillgs

    wkillgs Gold Level Contributor

    Need more info.... is this a brand new build? Did it always run like this? Did you change anything lately.... wires, carb? What ignition? Are plugs clean? The wrong base gasket on the carb will cause a huge vacuum leak.
    Big cams usually don't fit a stock engine unless you've made provisions for extra valve-piston clearance.
    A vacuum gauge can help diagnose other engine problems.

    Comp and Schneider also offer cams for a NH. You can even get a stock grind from NAPA. I'd recommend at least a mild performance grind.
  8. Stevem

    Stevem Well-Known Member

    You will never get any motor to idle right, or as good as it could be if the timing chain is stretched by more then 4 degrees, and many with over 30K miles are!

    To check this pull out all the spark plugs, remove the Dizz cap and spin the motor back & forth by the Balancer atleast 45 degrees, if the Dizz rotor lags behind when your Balancer rotation goes from one way to the other then its high time for a new chain and gears before convicting a Cam of being too big, or trying to set idle conditions!
  9. john m

    john m Well-Known Member

    Thanks for your replies cam spec is unknown but pulled off timing chain cover turned motor clockwise till I had tension on chain lot of slack on back side meaning one side tight other side loose any thoughts? Also found 2 broken outer exhaust springs cylinder 4 and 6
  10. john m

    john m Well-Known Member

    Sorry I was wrong exhaust on #4 intake#6
  11. wkillgs

    wkillgs Gold Level Contributor

    A little slack in the chain is normal. This one had 1/2" of slack on a replacement chain and gear set. Even a new set can have up to 3/8" slack or so. See if you can measure yours.
    If you still have the nylon coated gear teeth, you might as well replace with a new set.
    Not sure what causes the broken springs, but I'd guess over revving.

    gsgtx likes this.
  12. john m

    john m Well-Known Member

    Not over revved to best of my knowledge, but it does have nylon covered aluminum top gear ordered a new timing set will see . Thanks for advice
  13. 322bnh

    322bnh Well-Known Member

    Go to ebay and search "491 timing chain"...buy one sold in a long box (you cannot fold that one in your hand like the sloppy current production). It will be so tight that you will be cussing at me for recommending.
  14. wkillgs

    wkillgs Gold Level Contributor

    Thanks, just looked it up on the Sealed Power/Federal Mogul website. 222-491 is listed for 401-425 Buick. Also fits Ford 429-460.

    Carmen Faso once told me about the stiff vs 'folds in your hand' chains, but I don't recall which one he recommended.
  15. John Codman

    John Codman Platinum Level Contributor

    Are you positively sure that the outer ring on the harmonic balancer hasn't moved? Bring #1 cylinder up until you are absolutely sure that it is at Top Dead Center - it doesn't matter which stroke the piston would be on. If you are sure that the piston is at TDC, the timing mark should exactly be on zero. I have never seen an engine where the chain hadn't jumped a tooth or more that didn't run OK. Perhaps not great, but OK.

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