Flat camshafts

[chipis]

Hi, have been reading a lot about flat camshaft after engine rebuild, has anyone faced this kind of problem? If yes then maybe could provide some kind of advice or comments how to avoid it, what kind of cams has been used, oil, lifters were reused or put new? :coffee: as i did search in the forum didnt find any thread about this matter, maybe its not an often issue for renault c1j engine?

[allanr5gtt]

flat camshaft? do you mean running flat? (down on power)?

i had an engine that was holding back anything over 3.5/4k rpm turn out to be the cam was timed up wrong 180 degrees out?

[chipis]

I mean flat when camshaft becomes flat due to exceeded friction something like this:
http://www.youtube.com/watch?v=iJjcbqbinA4
not renault engine, but idea is quite the same

[Sparkie]

you mean you have worn out the lobe tip.

ive had it happen several times with piper cams. - so much so, i ground the bottom out of the follower, so i had to push it into the block to remove it! (it went like a mushroom)

several things spring to mind....

they were all regrinds - so the cam lopes were quite 'sharp'.
i had strong valve springs - i think they accelerated the wear.
i dont know if the regrinds were properly parkerised....

[chipis]

I have faced with it still. Im just wonder how to prevent from it, while using piper cams and stiffer valve springs, have read that it should be used engine oil with more percentage of zinc and phosphor, so switched to valvoline vr1 racing oil, which has almost tripple time more these additives in the oil preventing excessive cam lobe wear.

[DaveL485]

you mean you have worn out the lobe tip.

ive had it happen several times with piper cams. - so much so, i ground the bottom out of the follower, so i had to push it into the block to remove it! (it went like a mushroom)

several things spring to mind....

they were all regrinds - so the cam lopes were quite 'sharp'.
i had strong valve springs - i think they accelerated the wear.
i dont know if the regrinds were properly parkerised....

I remember you showing me that. The base of the follower looked like the top of a chisel where all the metal has turned over from the continued hammering :laugh:

[Scoff]

sparkie, could that have been valve bounce ? I can't think why the follower would mushroom from wear. ?

[TNT ANDY]

I remember an 8500rpm at one point. That may not have helped

[Sparkie]

sparkie, could that have been valve bounce ? I can't think why the follower would mushroom from wear. ?

the cam literally wiped the contact edge of the follower outwards. maybe it was valve bounce - it was along time ago now.

[Matt Cole]

Common cause is contamination on the lobe which then causes pitting. Heat then builds up in the damaged area and wear takes place. The problem imo comes from contamination of DIY rebuilds. Also remember the Piper instructions to bed a cam in at 2000rpm. Does everyone do this?:(

[Sparkie]

. Also remember the Piper instructions to bed a cam in at 2000rpm. Does everyone do this?:(

yes, but it still didnt matter. :(