Breaking billet cams?
 

I have a '99 P-pump 24v I'm working on for a customer. He just broke the second billet cam in less than 5000 miles. It is a name brand cam with all matching valve train. The engine is around 850 HP, not spun over 4k RPM. No fault was found the last time and I sent the cam to the manufacturer for inspection. They could not see an issue, but supplied me with new parts. I'm just trying to figure out where the problem may be, looking for any input.

That's interesting..

I guess that's one way of looking at it...

Cam bearings?

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What spring pressure? Just the stock cam bearings? Where's it breaking at?

103# springs. Yes stock cam bearings. It is breaking just behind the first journal. Well at least it did last time, and I'm pretty sure it did this time too because no valves are moving.

The bearings came up after the last failure. When I talked to the manufacturer he told me that with this setup I should not need bearings in all journals. There was no evidence of galling on the journals to suggest that it bound up and snapped. But I am wondering if maybe this has something to do with it.

Pump thrust is what causes breaks I seen , 850 hp and less than 4K should never break it .. did you install a new cam bearing in the front ? cam tunnel line boring and install bushings would be the place to start ..

We are talking steel cams right ? Is the crank gear welded if not it should have spun ,Better look at the injection pump also

Yes steel cams. The crank gear is not welded, and it was not spun last time. I haven't go it apart yet this time.

What's the piston to valve clearance @ overlap and no coil bind ? Look for Some way it's loading the cam what's the C/L degreed at . what year block ?

Not sure on actual piston/valve clearance at this time. Will have to check when I pull apart. Shouldn’t be cool bind with the cams and springs I’m using.


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Your missing something , take it apart and tell us what u find

Friend of mine snapped one in the exact same place when he was doing a dyno hit fogging the truck with a bottle. We had no idea it broke until we went to upgrade the cam and it fell off in our hands, jagged break and long bolt kept it together. We assumed it was from the nos hit.

Steel cam with the long bolt ?

Ppump drives so much harder and the helical gear strains the cam wanting to twist it sideways
U need a bearing support on the snout of the cam
PPD offers a nice setup but it’s gonna keep breaking it without it

This.

Is there something different about this setup? There's plenty of guys running 13mm pumps without supports, myself included, on a stock cam.

I got about 10 or more pulling engines i built all running steel cams with zero breaks few have seen 6,000 rpm

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.