525SC Miss/Backfire - Page 2

wannabe · 10-07-2009, 12:02 PM

At 420 hours your heads need to be redone. They are worn and you need new valve guides, and new valves put in. If you don't you will greade an engine by breaking a valve head off. Do both engines, it's time.

Wannabe

boatstogo · 10-17-2009, 08:45 PM

Well, finally realized that the valve was not stuck open, but the cam lobe was worn off to where there was a 1/4" play in the roller rocker/valve stem. Engine is now torn down and will do heads, rings and bearings although no evidence of wear or abuse on anything. Just found out Crane is out of business on Cams so will have one ground to Crane spec to match other two motors. What would wipe out cam on 450 hour motors that have rarely been run over 3000 RPM's?

ezstriper · 10-18-2009, 09:13 AM

for the most part since no new engines being produced have flat tappet cams, and emissions laws oil now has no zinc and the removal of it can kill flat tappet cams as you have, you need to find oil that has special additives or you will kill the new cam in a hurry...Rob

rdoactive · 10-22-2009, 10:12 AM

Google cam, zinc, & Rotella, you'll find your answer.
You may want to swich oil.