F1 cam thrust face broken? - Photo

ksoholm

ksoholm

Senior member
Location
Bellingham, WA, USA
Mates,

While checking the valve clearances, I took some photos that I reviewed shortly after. Discovered what looks to be a broken intake thrust face. How could that have happened? For some reason I did not see this until reviewing photos. Sure looks like the cam took a tumble at some point, or? Is it fatal?

Thanks-

Kristian

 

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Hi Kristian,
indention at the cam block pillar points to some ham-fisted bugger had given it a whack with a hammer, probably in an ill-fated approach to free up spinning of the cam. Fatigue crack due to the camsahft not being straight anymore might be another cause. But the shape of the cracked part does not really fit to a fatigue crack. Just take a closer look at the fractured surface, forced fractures have usually a satin like/silky bright appearance , whereas fatigue cracks have a more dark, smooth surface, showing often fine lines across the surface (rest marks).

Regards,
Stefan
 
ksoholm said:
Yes, was thinking something like that with the mark on the cam block. Don't know who would do something like that.

Thanks,

Kristian
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Neither do I, but I see this sort of crap all the time...  Wasn't me, guv'ner! ::)

Round the edges a bit so they don't scratch the cam bearing and your good to go.  I'd check the cams for run-out as well.

piet
 
Can't imagine this happening while the engine is running, at least not under normal circumstances.  Perhaps just a slip of the hammer... for whatever reason.  Maybe the cam fell from the workbench during servicing, or something similarly stupid.

piet
 
motoddrob said:
Is this a 120 cam? never seen anything like it before on any of the 180 cams I've played with.
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Yes.  The have a revised axial location in the centre cam brearing.

piet
 
Yep, cam out of '83 RGS. Removed it yesterday, found even more damage to the thrust flange, plus, center cam bearing looked bad, too. Thrust face had chewed a bit on the bearing. The cam is off to be fixed, we're lucky here to have a highly regarded camshaft specialist who'll weld up the thrust face. Otherwise the cam's runout is less than .001mm etc. Still can't for the life of me figure out what somebody did here, or why it seemed a good idea to stick the cam back in.

Kristian
 

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Less than 0.001mm runout, that's impressive!  :o  Don't think even the cam journal roundness comes that close...  Most cams I check have anything between 0.05 and 0.20mm runout.  I usually mange to get that down to +/- 0.01mm though.

I've seen worse cams and bearings that were still within factory limits, not nice to look at, but still quite servicable.  The cam has either run dry or a load of crap has been pumped through with the oil, might be worthwhile to check the oil pump as well.  What do the other cam bearings look like?

piet
 
I got a new bearing coming from Wolfgang, and cam was fixed for USD35. Amazing.

The other bearings look dandy.

I shall obey and take a gander at the pump, as I'm already in there awaiting a new clutch.

Kristian
 
And if you don?t find the parts on top of the cylinder head they might have fallen down the chaintunnel in the oil sump. Maybe you have a look and dismount the lower chain gard at the bottom of the engine.
 
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