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Old 06-20-2019, 08:32 PM   #1
427f2
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Default Thoughts on roller cam damage...

Looking for thoughts on what the cause of these cracks on the #3 bearing
journal are due to. There are 10-12 of these, all of them running in the
lengthwise direction. You can feel them with your nail and I would say
they are ~.005-.010" deep. They are only on this #3 journal.

Some background on the cam, it was in a previously running engine that
ran well with no problems and and routinely turned 8000rpm.

Application is a buick V6 that has an OEM journal diameter of 1.785" for use
in standard cam bearing inserts and this cam Was modified to be used in
a roller bearing block setup and the diameter was reduced to 1.772" or had
roughly .013" ground off the Diameter.

The cam turned easy in the block and the engine had no failure or other
known issues.

Needless to say I will be having a new cam made as soon as I locate a core,
But what should I look for to prevent a re-occurrence?

Was this one journal simply not hardened to a sufficient depth to allow under
support of the diameter reduction? This is my first go around with roller cam
bearings.

I also posted this in Chris Uratchko's section.

TIA.
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Old 06-21-2019, 12:45 PM   #2
CamKing
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Default Re: Thoughts on roller cam damage...

That is an induction hardened cam core, from either CMC or EPC.
On the induction hardened cam cores for engines running babbit bearings, they don't bother to harden the journals. I guess they save a few pennies, not having to run the coils around the journals.
I found this out the hard way, when one of my customers decided to switch his LS Daytona Prototype engines from 55mm babbit to 55mm roller bearings. I assumed the CMC cores we had been using, would be fine, until they weren't. I would have never guessed the cam core manufacturer would make a billet steel cam core, and not heat treat the journals. Especially when the journals are 55mm, and it's not much of a stretch, to think someone would put in 55mm roller bearings.
Now CMC heat treats the journals on their LS cam cores.
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Old 06-24-2019, 09:39 PM   #3
427f2
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Default Re: Thoughts on roller cam damage...

Quote:
Originally Posted by CamKing View Post
That is an induction hardened cam core, from either CMC or EPC.
On the induction hardened cam cores for engines running babbit bearings, they don't bother to harden the journals. I guess they save a few pennies, not having to run the coils around the journals.
I found this out the hard way, when one of my customers decided to switch his LS Daytona Prototype engines from 55mm babbit to 55mm roller bearings. I assumed the CMC cores we had been using, would be fine, until they weren't. I would have never guessed the cam core manufacturer would make a billet steel cam core, and not heat treat the journals. Especially when the journals are 55mm, and it's not much of a stretch, to think someone would put in 55mm roller bearings.
Now CMC heat treats the journals on their LS cam cores.
Thanks camking, are you implying that you think i have a journal hardness
issue?

I can see the heat rings from the induction process on that journal but maybe
its not deep enough?

I have a new core coming if you are interested in grinding it. I have an idea of
what I need but would be interested in your opinion.
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