Cam and valvetrain longevity....??? low duration high lift...
#1201
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From Harold Brookshire
There is a limit to how far you can regrind a cam, or even the initial grind.
Cams are made to a given lift, duration, and LSA, and then heat-treated, either carburizing (8620) or induction-hardening (other steels ending in -50 or higher). How long, and how deep, the heat-treat goes is very important. Many cams have only .080" or less of heat-treat.
Cams can generally be ground +/-3* in LSA, and +/- .025" in lobe lift. These are the more important numbers.
So this means you cannot regrind a .370" lobe lift, 106 LSA cam into a .450" lobe lift, 112 LSA cam. The grinding process with go through the heat-treat on both the nose, and on the sides. You can't grind a 106 LSA into a 108 LSA, then later try for 104, or 110. You'll go through the heat-treat.
If you keep the LSA the same, or just a 1* difference, keep the lobe lift close to the original, you'll be much happier. The actual shape of the lift curve has more importance than either of those two.......
I had also read, GM, had a spec of .180 deep when finished.
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#1202
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The quote above mainly talks about regrinding and the risk of going through the hardening. These cams are new so regrinding through the hardening shouldn't be a concern. The video you posted shows them being hardened after grinding I think. Seems like Cam Motion is the only one that would really know if they are up to spec based on their manufacturing technique. Even if they are grinding them to someone else's spec I don't think they'd let them go with what they know to be a defect which is what that'd be. Mine still look good. We had the chance to check everything when we were swapping intakes.
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Last edited by bck; 10-04-2016 at 10:50 PM.
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#1203
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The quote above mainly talks about regrinding and the risk of going through the hardening. These cams are new so regrinding through the hardening shouldn't be a concern. I think the video you posted shows them being hardened after grinding I think. I'd think Cam Motion is the only that would really know if they are up to spec based on their manufacturing technique.
Last edited by MILD THUNDER; 10-04-2016 at 10:47 PM.
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#1204
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I might throw mine back in the dyno and play around with exhaust inserts in the collectors. I need to find someone who really knows exhaust to get involved with that.
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#1205
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I could be wrong, but i don't think Cam motion, is grinding cam lobes, from bar stock. They probably get a series of lobe families, and have to grind off a certain lobe, to get their "custom" lobe. The cost, to manufacture a "one off" cam, from a blank piece of bar stock, manufacture it, heat treat it, then send it out, wouldnt cost 450 bucks.
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#1206
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Again after reading all this drama I'm so glad bob the cam numnuts didn't respond to my email. I could have pissed money in the wind like so many others. I'm sure he has a cam or 2 out there working. Even a blind squirrel finds a nut.
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#1208
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I'd like to cut one of comps and one of bobs right down the middle length ways and dissect them.
Just looking for answers. That's all.
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#1210
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I'll have to say my engines are pretty stout with MK cams, but they have beat the s#it out of my valve train. I never dynoed and maybe my heads have masked inadequate cams. I'm satisfied with the power, but upset about the lobe instability. I have snapped a few pushrod guides, trashed a rocker, gained lash and have have taken out a piston from a valve cause of lash. I have been mulling over the comp master lobe/cam book with my head guy the last few days.
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