Me off all people...Cam and lifter failure

[mike_elliott]

NIce idea, but it won't really work because the "intake" hole on the cam for the oil is only a hole at one location, so it picks up oil every revolution...it is not a continuous supply that could oil the lobes without engine rotation.  The pre-oiler will only guarantee that the oil supply is ready to be pushed into the cam before you turn the key, and of course get the oil out much quicker.

If the Centrilube folks would lathe a groove in the cam bearing surface where the "intake" hole is, it would provide constant oil flow thru the cam. Now we may have to adjust pressures elsewhere to keep rod ends from oil starving, etc, but heck, we could solve the "we don't need no steenkin' camshaft lubrication" design of the lyc's that way 

[Alan Fox]

You cant groove the bearing surface on the cam , because the cam has to spin the lifter , and that has to do with the contact point between the cam and lifter....

[jetdriven]

If you mill a groove in the rear bearing journal, that doesn't affect the lifter but will provide full-time oil to the hollow cam. However, doing so effectively converts the rear cam bearing (the case, actually) to two separate bearings of slightly less than the full width, and has to be analyzed. It increases the oil film load in that area.

[Alan Fox]

Ok , I thought you were talking about the lobe.......I have seen cams that have grooves in the bearing...., a groove there would not be load critical........

[jetdriven]

Here is some more info from CASA about lycoming lifter failures.

http://www.casa.gov.au/wcmswr/_assets/main/airworth/awb/85/014.pdf

[mike_elliott]

Here is some more info from CASA about lycoming lifter failures.

http://www.casa.gov.au/wcmswr/_assets/main/airworth/awb/85/014.pdf

 

helps make sense out of Lycomings policy to give a substantial core credit if your engine has been in their shop within the last 12 years and why when you order a rebuilt, you get a roller cam engine back. The Lawyers have their input.

[DaV8or]

Here is some more info from CASA about lycoming lifter failures.

http://www.casa.gov.au/wcmswr/_assets/main/airworth/awb/85/014.pdf

 

Would love to know more about what was going on in the picture that showed the roller cam failure. No mention in the bulletin and I have a hard time believing that was due to corrosion.

[jetdriven]

Yep thats concerning. I have seen a couple pictures of roller camshaft lobes with corrosion damage, but the roller seems to tolerate that well. That photo in the PDF of the roller cam damage is a heck of a lot worse than that. I keep searching for evidence of widespread roller cam failures and there are dozens of photos of flat-tappet cam spalling, very few of roller cam failures. However, seems nothing is bulletproof in these engines.