Breaking billet cams?

After taking shipment of cam, make sure it's straight.

A good engine builder should be able to check and straighten one...
 
DISTURBED said:
My gut says this isn't a billet steel cam. I can't remember the last time I heard a billet steel cam breaking. Cast is a different story.
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X2

Two years ago I had a customer with a 2.5 engine, 4v with a 13mm. He broke a cam similar to what you are describing, one look at the core, never again will I install that brand cam in a competition build. Since switching to no limit cams, I haven’t had any questions, concerns or problems.

And 103# at what height? That number means nothing. I understand that it’s advertised as such, but testing springs at the installed height is crucial, imo....

I’d be inspecting the gear lash and thrust on all components, the clearance between the cam and journals, straightness of cam,,, exc. pretty standard assembly.
 
DISTURBED said:
My gut says this isn't a billet steel cam. I can't remember the last time I heard a billet steel cam breaking. Cast is a different story.
Click to expand...

You are right, I should have just said steel cam. Most of them are advertised as being machined from new steel billets, but I believe it is a cast steel blank. That being said, the manufacturer claimed to have not seen another one break without other mechanical failures causing it to bind and break.
 
TheHammer said:
X2

Two years ago I had a customer with a 2.5 engine, 4v with a 13mm. He broke a cam similar to what you are describing, one look at the core, never again will I install that brand cam in a competition build. Since switching to no limit cams, I haven’t had any questions, concerns or problems.

And 103# at what height? That number means nothing. I understand that it’s advertised as such, but testing springs at the installed height is crucial, imo....

I’d be inspecting the gear lash and thrust on all components, the clearance between the cam and journals, straightness of cam,,, exc. pretty standard assembly.
Click to expand...

Ya I'm starting to think I shouldn't trust what I am being told by the manufacturer. I trust my engine builder and have not had this type of issue over multiple builds in the past. I will certainly be checking all those things when I tear it down. Thanks for your input.
 
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a1eadfb9416dff9837307e3854e6091c.jpg

Here’s a few pictures of the first broken cam.


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OK, after seeing pictures, I'm sticking with my first thought, I believe this is a gear out of concentricity, and cycling side load as it rotates. I would look for an odd or dual wear pattern on the cam gear and those in mesh with it.

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For the sled pullers/big setups on this thread running no limit, are you guys running the plain steel ones or the tool steel cams?
 
TheHammer said:
X2

I’d be inspecting the gear lash and thrust on all components, the clearance between the cam and journals, straightness of cam,,, exc. pretty standard assembly.
Click to expand...

This. I've seen cases where the block has been linebored incorrectly, reducing cam gear backlash, and breaking the cam as a result.
 
Adjustable pump gear by chance? The last one we installed on a 3.0 truck was built very far off center. The Gear would get tight enough to hardly rotate the engine on one side.
 
My bet, he's coming out of the fuel hard and unloading the drive strain on the cam is causing this. It takes a lot of power to drive a good P-pump, and when you unload it quick it can be a shock...Why it isn't drilled to the second journal is beyond me, everyone knows that is a must on a P-pump.

Junk cam, IMHO
Chris
 
Is that a steel retainer?

That cam looks like it was hardened very deeply, is it 8620 steel? Is the gear a stock 12v gear like the cummins dodge engine uses?
 
Another quick thing to check is the front gear housing. If it isn't a genuine Cummins housing that could be your issue. A lot of the Asian knockoff housings aren't machined correctly and cause gear misalignment/ mesh issues as others have said.
 
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