Were the lifter trays changed out with new GM ones? A lifter that is allowed to twist will chew into any cam. Was their scuffing on the related lifter wheel? Did you check the hardness of the lifter wheel as well? Curious

 

Yes. I always install new trays, and nothing but genuine GM trays that I pick up personally at the Chevrolet dealer. They come in sealed bags. Did not check the wheels for hardness. There was no wear that indicated they were soft. I was going to reinstall 14 of the 16, and buy 2 new ones, to avoid chances of getting a defective lifter. But Tony@Mamo Motorsports suggested running Johnson lifters, so I bought some 2110Rs from him. GREAT guy, and great company to work with. Best customer service I've ever seen...

 

So, explain this hardening process. Just heat? Quick cool? Any kind of coating before or after the heat. Dumb this down a little...you know who you're talking to

 

Hi, OM! I have a lot of respect for your opinions and experience. It has been awhile since metallurgy classes, but IIRC, it isn't coated, and the heat is generated electromagnetically. They use it to heat selected areas of a metal, like cam lobes, while leaving other parts somewhat softer. They quench in water, or maybe oil. Since my bearings were harder than the lobes, IDK if CM uses induction hardening, or not. This is sure a complex situation. I've always liked CM, otherwise I wouldn't have bought 2 of them. I'm just hoping we can find the root cause, and we can all learn something....

 

Guys,

More "learning" as I have just measured all of Grinder's springs on a very accurate Intercomp valve spring tester

I will admit I was surprised to see how well they hung in there with the amount of miles on them. For a more affordable valve spring you certainly cant complain one bit....Im impressed actually

At 1.800 the installed seat pressure varied from 149 - 161 (advertised at 160 @ 1.800). Note I didnt actually measure their original installed height because I got the heads disassembled from Mike but I was informed they were set up at 1.760 so even the weakest spring at that height measure 164 lbs on the seat

With Mikes OEM rockers and the cam he had I would say with a high degree of confidence that reduced spring pressure (and potential valve bounce) wasn't the cause of the issue. This assumes smoother cam lobe designs and I don't have any info on those particular lobes but for the spring to last this long the lobes must have been smooth.


Btw the rate of the spring was advertised at 392 lbs per inch.....even the weakest spring came in at 420 lbs per inch (which is somewhat common....in the sense I see quite a few springs from the higher quality spring manufacturers come in above stated spring rates).

What else....hardness test on the cam lobes....to me it makes sense the really worn lobe had the lowest hardness as it had the most material removed. Surface hardness only goes down so deep and with more material gone the material that was left should have shown a lower hardness value

A big reason I was never a fan of cutting cranks .010 under....while you get the journal nice and round again the actual surface of that journal is softer than what it was at the OEM diameter due to the depth of the material cut and a lower hardness at that depth.

Also the depth of the heat treat is really dependent on how the part is heat treated so that's a moving target also

Anyway....we didnt find the smoking gun with the spring testing and good on PAC Racing to offer a spring at this price providing that much longevity

I don't regret pushing Mike to go with the higher quality 1200 series though....too much riding on the springs to save a few bucks there if your goal is trying to get yourself the most reliability possible

Not to mention I pushed the lift up a bit on the new cam and the better spring is just the right call for this build for many reasons

Mike....Im going to toss these in the trash....I assume your good with that!?

Regards,
Tony

 

Yes, trash them, please. They're still within spec, but as you well know, they have a cycle life. Hats off to PAC!! They do make some damn good springs. Still can't say with 100% certainty that it is the lobe, but this is another arrow pointing in that direction. Thank you for all of us for doing the testing. I'm sure many here will appreciate it, as well.

 

Following. I have a fresh motor with a titan 3 ls7 cam in it. Would love to find out what happened to yours.

 

I think the hardness test pretty much confirms what happened. That lobe was just too soft. When you get 15 heels that come in at 56-58RC, and the one with the really bad lobe is the only one that comes in at 30-32RC, IMHO, that pretty much tells me that lobe just didn't get hardened correctly....

 

curious which core type your cam is ?

 

I don't know. It was purchased as a custom grind thru Allan Futral@Futral Motorsports. It was drop shipped from CM to me. No specs on the cam core. Only the usual lift, duration, LSA, and degree specs.....

 

Quote leads me to believe he was asking me but from your pics it looks like a 5150 core from the lack of copper on the sides of the lobes.

Actually I take that back. Can’t tell if the orange-brown is varnish or not. Could be an 8620.

Mine is a 5150 core. I haven’t even gotten to see the full potential yet either. Really excited as it’s not exactly a small cam

 

We only buy the 8620 cores from Cam Motion if that makes any difference to anyone.
Over the years Ive seen bad cores/lobes from every single cam shaft manufacture but have not personally experienced a bad lobe on an 8620 core.


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