MILD THUNDER

8620 is carborized to 60-62rc scale, .100" deep. Thats Mike Jones spec after he heat treats a camshaft.

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.

bck

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.

MILD THUNDER

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.

bck

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.

bck

They have certain cores that can handle a given range of profile so I guess the get them partially machined then pick the core that will work for the desired profile.

Crude Intentions

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.

Crude Intentions

It to mention browsing cam motions site they are all about Ls series stuff. I'll stick with comp, lunati, or howard.

getrdunn

They should be equal to or greater than any other reputable cam company who grinds custom billet cams. Pretty much all the major cam companies. Be rather simple to find out with the right equipment. No reason not to find out. Marine engines run hard and under a constant load for long distances that can build heat in internal moving parts that can cause problems. The grinds in discussion see more abuse than ordinary cams due to the lobe design. The real concern here is the hardening process. Compare one of these billets to another. More than one thing to check. In regards to CM doing the grinds for Bob yes and no what you were referring to. CM are grinding and hardening to what they are told via work order or bobs normal standards which isn't necessarily the same as jegs, summits, as an example. Who knows who all they grind for. Probably more than we know.

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.

getrdunn

Other thing is you can run solid springs and rollers on comps hydraulic rollers years on end with no issues. Just saying and just wondering if.....

Rookie

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.