Which part does the "wearing"?

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MopaR&D

MopaR&D

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General question about flat-tappet cams... during the break-in period is it the lifter faces or the cam lobes that wear off? Whenever i hear talk about proper break-in it sounds like both parts wear together but then that wouldn't make it possible to use new lifters on an old cam right? Also the cam is made from cast iron and the lifters from steel i'm guessing the cam is the harder of the two?
 
Just from observation of worn parts, they both wear. When something goes bad, you can see problems on both parts. The cam surface is hardened, and so always seem to wear more slowly (again, just based on what I have observed on used parts).

You can use new lifters on a used cam because the new lifters have fresh convex surface on the bottom, that will promote the proper rotation when working against the taper across the cam lobe surface, and a performs new break-in process. But if the taper is all worn off of the cam lobe, then the cam is likely too far worn to re-break-in.

Interesting discussion here:
http://www.enginebuildermag.com/2009/04/flat-or-tapered-cams-and-flat-or-crowned-lifters/
 
I never heard of people wiping a lifter, but I hear of them wiping lobes
that would leave me to believe that if anything wears more quicker then the rest, it is the camlobes
 
Well for what it's worth, I have a solid lifter cam right here, and the wear signs are on the lobes. Looking at the lifters, I see nothing, and when holding them together (end to end) they still have a smidge of daylight on both sides.
 
It's both. The extent just depends on how long you drive it that way.
 
Proof. Both are shorter than stock, came out of same motor, and were installed at same time. Lobes were wiped on both.
 

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I have seen a cam wiped out AND the lifters so bad I could not get them out of the bores. Cam goes first I think. :burnout:MT
 
Getting those lifters out was a challenge. Scrapped the block so i wasn't worried about lifter bores. Had to pry em out. this is why it's a roller cam world for me from now on.
 
Well I've managed to wipe both at the same time, but only on an Oldsmobuick so no loss there. Generally though you can wipe a lobe pretty easily.
 
Different cams are made from different materials too, so I'd say it's a toss up. Had a friend with a late 70's Vette that was known to have soft cams. Ground a lobe down to a circle so the valve wasn't doing anything. Cams can be cast and billet as well, which I'm sure has some effect on their durability.
 
I have pulled some badly concave lifters on lobes that had not yet fully failed. But that one in the pix above takes the prize....zowiee!
 
Interesting stuff guys thx. So it sounds like they're both similar materials hardness-wise. I just got to thinking about this stuff because i have 20k+ miles on my current voodoo cam and i'm curious about the longevity of it since it's a fast-ramp design.
 
Seems like a good thing to think about. Maybe pull the lifters and inspect them and look at the lobes. Agreed on the fast ramp.... I think they are a good idea, but shied away from them on our latest build for my son's 340; he is less inclined to inspect things (Actually I was just the same at his age....let's just run it!) and he is not as philosophical about things failing and needing a rebuild.
 
Wear shouldn't be an issue on a fastramp cam, that is more of a hammering or poor valve controls issue.

If you got that far with it, seems it is golden to me
 
The parts need to be the same hardness. The break in establishes a mutual surface roughness that lets the oil protect the individual faces. If at any point down the road the oil isn't between the parts, the surfaces get damaged, which makes it harder for the oil to continue to protect the surfaces. And then they both scrub off. You want "just enough" spring pressure at the break in rpm to allow for the surfaces to wear together, and once that's set, you want enough to control the valve motion through the entire rpm range. That's why the instructions say to remove the inner springs.
 
jos51700 said:
Proof. Both are shorter than stock, came out of same motor, and were installed at same time. Lobes were wiped on both.
Click to expand...

What oil were you using? I think both wear but, I also think the lifter goes first. Spring pressure has a lot to do with wear. Try finding a small block Chevrolet lifter that has any crown. Don't bother, I've never seen one.
 
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