Knocked a lobe off of a cam? In here!

Nxcoupe

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Hey all, anyone knocked a lobe off of a cam here recently? It's been years since I've had one do this, so I don't recall the exact symptoms.
Did that have tapping noises? Just the misfire with no noise? Thanks in advance.
 

Kern Dog

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I had TEN lobes in varying stages of destruction.
The first symptom was increased clatter from the rocker arms. Power was down and the idle got rougher. I pulled the valve covers to find several loose rocker arms. I had a MP 528 solid with adjustable rocker arms. Tightening up the loose rocker arms didn’t help. The wear had already started.
 

INTMD8

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Nope. I read enough threads here to make me paranoid enough to go roller.
 

Nxcoupe

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I had TEN lobes in varying stages of destruction.
The first symptom was increased clatter from the rocker arms. Power was down and the idle got rougher. I pulled the valve covers to find several loose rocker arms. I had a MP 528 solid with adjustable rocker arms. Tightening up the loose rocker arms didn’t help. The wear had already started.
So that tosses that theory out the window! I have complete silence but have a definite issue on #7. Next up is to check spring pressure. Could be the one that was hung open for 21 years.
 

Nxcoupe

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You CAN get wiped lobes with no noise....
Now that I think about it, yeah, if the lifter doesn't wear, the base circle will be unaffected and therefore no reduction in preload. Is that what you are saying? It's not very likely, but I guess it could still be early on in the wiping, so to speak. I am still going to pull the valve cover and inspect the springs and lift of the rockers on that cylinder. Strange it's only one cylinder.
 

toolmanmike

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Just curious, what cylinder is it?
 

Geoff 2

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Nx,
Post #8.
Yes.
I rebuilt a 455 Pontiac engine last year to fix oil leaks; it idled reasonably well & made no noise; upon teardown one lobe was severely worn. Whether you get noise will depend on how much wear occurs & how much 'spare' lifter travel there is. Most hyd lifters have around 0.180" of internal movement.
 

Nxcoupe

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Nx,
Post #8.
Yes.
I rebuilt a 455 Pontiac engine last year to fix oil leaks; it idled reasonably well & made no noise; upon teardown one lobe was severely worn. Whether you get noise will depend on how much wear occurs & how much 'spare' lifter travel there is. Most hyd lifters have around 0.180" of internal movement.
Thanks, it also has a weird sound out of the exhaust. It reminds me of when a valve spring broke on my 440 years ago, but could also be caused by a wiped lobe I suppose. After the belvedere is back on the road, I'll get the valve cover off and inspect.
Thanks to all that responded.
 

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