Camshaft and Lifter Failure Causes

Here is a list of items that are contributing factors for a flat tappet camshaft (new or otherwise) and/or lifters to experience a premature failure.

  1. Lubrication of cam and/or lifters is inadequate before first startup
  2. New engine is turned over excessively before being initially started
  3. New engine sat too long before starting it for the first time
  4. Engine is not at a sufficient rpm during camshaft break-in
  5. Valve train geometry is incorrect
  6. Valve to piston clearance inadequate
  7. Retainer to seal clearance is inadequate
  8. Valve spring coil bind
  9. Valve spring pressure is excessive
  10.  Pushrod tip angularity (at rocker adjuster)
  11.  Tight valve guides – inadequate valve guide clearance
  12.  Lifter crown radius – improperly ground
  13.  Camshaft lobe rake angle incorrect for application
  14.  Reversed camshaft rake profile – rakes on wrong side of lobe
  15.  Camshaft lobes are cut on too small a base circle – lifters too far down
  16.  Connecting rod contacting camshaft – stroker issue
  17.  Pushrods rubbing or intermediate contact within the heads
  18.  Incorrect valve lash
  19.  Rocker arm drag at shafts or trunions (oiling, clearance, etc.)
  20.  Loose cam gear retention bolt(s)
  21.  Camshaft end play is excessive
  22.  Oil quality (inadequate zinc / phosphorus content, incorrect application, etc.)
  23.  Contaminated oil (water, gasoline, particulates, etc.)
  24.  Oil pressure insufficient
  25.  Lifter bore too tight, lifter doesn’t turn or work freely
  26.  Lifter bore alignment (cam blank & block manufacturing issues)
  27.  Use of used lifters on a new camshaft or in a different block
  28.  Mixing the used lifters within an engine, not staying on same lobes
  29.  Excessive low speed idle time
  30.  Engine sat too long with open valve spring load on the lifters
  31.  Incorrect or inadequate heat treat on lobes and/or lifter faces
  32.  Valve float – bouncing and/or hammering the lifters on the lobes
  33.  Use of ARP fastener lube on the lifters and/or lobes; simply the wrong lube
  34.  Using high viscosity lube on lifter shanks; keeps lifters from free turning
  35.  Lifters are reground to the point that the original surface hardness has been compromised.
  36.  Rocker assemblies have been installed without backing off the adjusters thus jamming the lifter against the lobe due to coil bind or other interference issues.

While this list is not in any particular order of importance, any one of these items or combination of them can contribute to a cam lobe or tappet failure.

Until next time, Happy Y Motoring. Ted Eaton

Addendum:  While having an adequate level of ZDDP content in the oil is important, examination of those engines with camshaft and lifter failures finds that those failures are more often the result of other issues not related to the Zinc/Phosphate levels in the oil.  Current available oils if properly selected based on the information in the API bulletin do still have adequate amounts of Zinc/Phosphate for the older flat tappet camshafts.  The key here is to know which oils have had the Zinc/Phosphate amounts reduced and which have not.  This essentially means reading beyond the first paragraph of the API bulletin to get that information.  Ted Eaton, November 2012.

Addendum:  Items #33 & 34 added after initial publication in YBM.  Ted Eaton, May 2015.

Addendum: Items #35 & 36 added after initial publication in YBM.  Ted Eaton, Dec 2015.

This article originally published in Y-Block Magazine, Issue #112, Sep-Oct 2012, Vol 19, No.5