Scoring on cam lobes

merkyworks

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I've had an intermittent ticking noise for a while now and figured it was just the normal ticking noise that others have complained about. It comes and goes from the passenger side and since that valve cover is easy enough to remove I thought what the heck I would give things a look, maybe it was a lash adjuster going bad or something easy to find. I didn't find any bad lash adjusters, however I did find that some of my cam lobes and follower rollers had score marks on them! The surface of cam lobes and the follower rollers isn't rough and I ran my finger nail across the score marks and it didn't catch so they are very shallow but still WTF, motor only has 35k miles on it.
Capture.JPG Capture1.JPG


Researching GT500 cam scoring I found two other instances with near identical marks. For people who have rebuilt their engines or done cam swaps, did you see the same type of wear? Is this considered normal cause I could only find instances of this happening on GT500 motors, 4.6/5.0 4V motors the cams look perfect.

Find #1 - SVTP post from 2010
"My engine builder told me it was less than .003" so nothing to worry about, just some scarring."
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Find #2 - JDM Blog from 2017
"Once we had the valve covers removed, we could see that there was excessive scoring on the lobes of the camshafts, rockers, and rollers."
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Catmonkey

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I didn't have any wear like that on my cams when I installed the 5.8 and a subsequent re-cam, but I have a lot less miles too.
 

RBB

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I had some scoring when we pulled the heads off for an engine swap at 40K miles. Cam journals needed a line bore to clean up the score marks. Looked very similar to that pic from JDM.
 

merkyworks

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I had some scoring when we pulled the heads off for an engine swap at 40K miles. Cam journals needed a line bore to clean up the score marks. Looked very similar to that pic from JDM.

So now the makes 4 instances of the scoring. Was your engine blown or was it still in good condition?

I could be totally wrong on this but I'm wondering if maybe the cam towers on GT/GT500 heads are causing this. At certain loads or RPM the cam towers are flexing.

If you compare the cam towers on 4V heads (left to right), 03-04, "B", GT/GT500 you can see the GT/GT500 heads are the only ones without a cam tower girdle.
2016-07-18_22-03-34.jpg

Then when you look at the Coyote 4V heads you can see the cam towers are positioned fully inside the head and not sticking up like older 4V heads. Doing this would eliminate any need for a girdle and would not allow the towers to flex.
2016-01-06_22-38-56.jpg

Just a thought, like I said I could be way off on this.
 

RBB

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So now the makes 4 instances of the scoring. Was your engine blown or was it still in good condition?

I could be totally wrong on this but I'm wondering if maybe the cam towers on GT/GT500 heads are causing this. At certain loads or RPM the cam towers are flexing.

If you compare the cam towers on 4V heads (left to right), 03-04, "B", GT/GT500 you can see the GT/GT500 heads are the only ones without a cam tower girdle.
View attachment 1485080

Then when you look at the Coyote 4V heads you can see the cam towers are positioned fully inside the head and not sticking up like older 4V heads. Doing this would eliminate any need for a girdle and would not allow the towers to flex.
View attachment 1485082

Just a thought, like I said I could be way off on this.
My stock engine was totally fine, running strong. I'd been putting a lot of 1/4 mile passes on it over the last few years at a much higher power level than stock and decided to upgrade before I blew the thing.

I can see the logic behind your assumption here....makes sense. I can tell you the guys at JDM said this is not uncommon on GT500 heads with some miles on them when we spoke about a line bore to clean up the scoring.
 

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