Ruined cam - how?

Hey guys, I have this camaro in the shop (from another local speed shop) and it was backfiring out the intake. Well, we immediately checked the rockers and found out one of the exhaust rockers not moving, got it nailed down to a broken lifter/roller.
It ruined the intake too, burned that runner up where it meets the head and burned the injector tip off.

We pulled the cam and all lifters for inspection and how does this happen?
All the lifters have some sort of damage or pitting to them, some of the lifter lobes are ground pretty good (see pics).

Cam bearings look fine.

reground camshaft? Looks like the broken lifter may have turned in its holder/guide. Once a piece of metal gets into the air inside the engine then it keeps bouncing around until its pulverized into nothing.

Bad cam bearings?

Coil bind or excessive spring pressure can cause that type of failure.

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Originally Posted by Madd Maxx

Coil bind or excessive spring pressure can cause that type of failure.

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We replaced the lifter plastic guides too, just in case.

From the markings on the back, I can see it's a Torquer II cam, and it appears to have Patriot double springs, combination sounds about right.

We're installing an LS6 cam and new lifters for now, keeping the P springs.

I thought about excessive spring pressure as well, I thought about changing in the springs to a 918 or LS6 spring.

sure looks like some coil bind and lack of oil. What springs were on the heads? Just looks like there wasnt any lubrication and caused the lifter to turn sideways resulting in the roller breaking off. It is weird that all the rollers have some damage.......that is what leads me to believe it is a lubrication issue. Are the valves/pistons ok........maybe clearance issue?

Could be like RED said.....regrind cam....along with incorrect pushrods and coil binding. Let us know what you determine!

The stock cams do that too.....usually higher mileage but I replaced the cam in a GMT900 2007 6.0 3/4 truck with less than 40K miles on it a few weeks ago. Looked just like that on ONE lobe only. My theory is improper heat treat. After the lobe wears down with a channel, the roller supports on the side of the bottom of the lifter start contacting the lobe. That in turn breaks the lifter.

What about pre-install damage? Like stuff got dropped. Or maybe wrong part was put in. Or stuff didnt get torqued down right.

Possibly. Dropped? I think anyone should spin the shaft in the bearings before reinstalling the chain and gears. That would tell if it was tweaked. I thought Allen said the valvetrain seemed to be adjusted properly....yet the pushrod (not the rods David...LOL) was loose on the E valve on that cylinder.

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Originally Posted by GasGuzzler

Possibly. Dropped? I think anyone should spin the shaft in the bearings before reinstalling the chain and gears. That would tell if it was tweaked. I thought Allen said the valvetrain seemed to be adjusted properly....yet the pushrod (not the rods David...LOL) was loose on the E valve on that cylinder.

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Maybe push rods were the wrong size. Looks like the lobes on the cam have a lot of wear.

Pushrods are good, no wear on them, they are straight.

All I can think of is this car may have experienced a lack of oil at some time.
The owner did buy this car used, he said it always had some going on with it and now this. Maybe the oil pump died at one time, who knows.

thanks guys,
allen

Too long of pushrods would hurt the plunger in the lifter, the rocker arms, the valves....something else. This was a soft cam and the wear broke the lifter.

Quote:

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Originally Posted by Madd Maxx

Coil bind or excessive spring pressure can cause that type of failure.

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First thought...

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Originally Posted by carfreak07

....that is what leads me to believe it is a lubrication issue.
Could be like RED said.....regrind cam....along with incorrect pushrods and coil binding. Let us know what you determine!

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Second thought...dammit guys--got to this post before I could say something--but good advice! Yes, on a regrind, the heat treat on the lobes make it harder--and with it being ground off in certain sections, it makes it susceptible to ruining the roller on the lifter. I saw this happen to Alan's cam when we tore down his motor...the cam lobe got flattened out because of oil starvation (because the lifter was not articulating up and down properly) and the roller from the lifter just sat on the cam lobe and it mushroomed the lifter.

Quote:

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Originally Posted by GasGuzzler

This was a soft cam and the wear broke the lifter.

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Exactly. Regrind cam...ruined lifters. Also a possibility of lubrication starvation at some point. I now honestly don't think there was excessive bind from the valve springs or wrong sized pushrods. It has all to do with a soft cam (and it having the XER lobes which = high ramp rates) and ended up messing up the lifters. You are going at it the right way Allen... If you are doing an LS6 cam, the P springs may be too much...good call on the LS6 springs or 918s... :thumb:

You sure tyler didn't get ahold of this project allen?



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