Why did I wipe out a cam lobe?
 

In early September we went for a ride, and did a couple of full throttle blasts about 30-45 seconds each. We were running about 5100 RPM, no big deal. Then we went crusing, at about 2800 RPM, then entered a no wake zone for about 15 minutes. We went back on plane, running about 2800 or so and the engine started sounding sour. I stoped, opened the hatch, saw nothing abnormal and went to get back on plane. It starting backfiring through the carb. Needless to say we idled back to the marina, about an hour away.

Today we finally got a chance to tear the engine down, and found a wore out cam lobe on #5E. The lifter, (flat tappet) was very much concave in the center. What a shock, I expected to see a broken valve spring! The cam has about 125 hrs on it, great oil pressure, no excessive engine tempatures, and acturally very light spring pressures. Why would this cam wipe out after this length of time? Any ideas? We are now tearing the whole engine down to clean up any debris. This is a normally asperated 461 BB. that dyno'd at 440 HP. This engine ran great!

Re: Why did I wipe out a cam lobe?
 

How many hours on the engine?
Was the cam broken in properly?
When the cam was new were new lifters used?
Fossil or synthetic oil?

Re: Why did I wipe out a cam lobe?
 

The engine was a completely rebuilt about 200 hrs ago. Yes, we broke the cam in on a dyno very carefully. I use Mobile 15-50 oil. It was broken in on 30 weight conventional oil, changed after the dyno pulls to 40 weight conventional oil and converted to Mobil One after about 25 hours. New lifters were installed with the new cam.

Re: Why did I wipe out a cam lobe?
 

Seen it many times, usually caused by a lifter bore being tight, not letting the lifter to spin in the bore. With 125 hrs on it , this would be unlikely unless a piece of debris worked its way between lifter & bore. I have seen (a while back) ,that a certain cam core supplier were having alot of problems with this,but have not seen one in a year or two. Make sure to check lifter bore for size & staightness,making sure it does not have too much clearance.....good luck

Re: Why did I wipe out a cam lobe?
 

Well, you came up with all the right answers. Kevin seems to have a handle on this. I bet he'd love to see the bottom of that lifter as much as I would!

Re: Why did I wipe out a cam lobe?
 

When we removed the lifter, that was my son's first comment, hey it still turning in the bore! Yes the lifter was perfectly concave. Maybe I can get a picture of it. I'm wondering after this long after the installation, if the camshaft may have had a "marginal" heat treat put on it. In other words close, but not perfect and this was something that would not show up immediately. Does that make any sense? Or, could there be a problem further up in the valve train causing undo stress on the lifter/cam? What would be the chances of improper lubrication at that point be also? The other lifters look good.

Re: Why did I wipe out a cam lobe?
 

Check all the spring pressures very carefully. Especially that cylinder. (check if low). Then measure the guide clearances on that cylinder too. Check the valve stems and keeper grooves for any damage. Weak spring or sticking valve making it bounce maybe?

Re: Why did I wipe out a cam lobe?
 

Every wiped lobe I have seen , had a concave lifter. Its a mystery wraped in a inigma. Because I never could find a problem with most of the lifter bores either. i would think the concave comes from drag...spin....drag....spin. But if you think about it , all it would take is a tiny flake to come off the lobe.....then not enough oil film thinkness to keep the two metal to contact each other........just a matter of time......you know the rest...

Re: Why did I wipe out a cam lobe?
 

Whiteknuckle,
There was a discussion recently about this topic and cam spalling is the most common cause for post break-in (belated) lobe/lifter failure. If you need more information shoot me an email. I will be back after PRI
Bob
http://www.offshoreonly.com/forums/s...ad.php?t=83665

Re: Why did I wipe out a cam lobe?
 

RMBuilder,
Thank you, that was a very interesting thread. My camshaft was an Ultradyne. I was very pleased with the way this camshaft performed, but obviously there may have been some quality problems. Like someone else said, they are not in business anymore. Now, I have to decide if I want to go to another flat tappet camshaft or invest in a hydrualic roller. We still do not have the camshaft out of this engine yet, it will be interesting when it is out to examine the other lobes more thoroughly.