Evo8 ftw?

 

Hmmm, this reminds me of the Tundra 5.7L V8 issue. I'm not sure how many camshafts actually broke, but Toyota recalled all the trucks to replace/inspect or whatever it was they did. I'm kind of surprised in the vendor attitude that basically says, "Hey, no need to panic just yet, let's wait until we have more evidence." Meanwhile broken cams keep trickling in.

I'm not even a IX and I'm considering not purchasing a cam from these manufacturers simply because of that.

 

Maybe more energy can be placed on investigating the cams with hopes of clearly pinpointing cause of failure. Like similarities or differences between fracture surfaces (i.e., shearing in CW or CCW direction), patterns of maintenance just prior to failure (e.g., if cam was ever removed and reinstalled prior, bolt removed with pneumatic tool), torque value used when installing, if thread lube was used on threads, and so forth. And just to rule out the very unlikely possibility of surreptitious activity, not saying there's any charlatan enthusiast out there, just putting everything on the table.

I can't imagine how a normally operating drive can place enough twist to make a solid rod snap, could be a defect precipitated during installation? Any testing done on random sample's just to see what torque value each cam can take before breaking?

 

this makes me think...


and to the person who asked what springspeople are using... I was running supertech springs headstuds and retainers... and at maybe 5k light throttle when it happened

 

man this is scaring me into getting cams now. these threads are popping up everywhere it seems like. the top 3 choices for me were GSC, Cossie's, and Kelford's. this sucks!

 

nononono... I think its a infeasible that the torque generated by the belt or the cam bolt are what cause these failures. It seems that based on the type of failures we are seeing here with MIVEC cams all breaking at the same unfilleted groove, that the failure is not due to extreme rotational force. Like you say twisting along its axis of rotation and breaking a cam rod would take immense force, and it is extremely unlikely that a timing belt with rubber teeth would be able to exert that kind of force. As the weakest point in the link, the rubber teeth would be shaved off first.

Instead what seems to be happening is that there is a force that is acting on the cam gears as the tension in the timing belt pulls down on them. Now this force coupled with the fact that these cams seem to be weak at the oiling groove means that there will be a stresspoint that occurs right at the inside sharp edges of this machined groove. As the cam rotates, the vertical force generated by the belt stays pointing in a constant direction (down). This spreads the stress around and around weak groove and eventually the cam gear snaps off due to fatigue.

And just to support my hypothesis, my qualifications are a Masters in Mechanical Engineering (Automotive specialty) from U of Michigan Ann Arbor. I work full time with engines testing and calibration. Without seeing the parts in hand and without testing in a lab nothing can be claimed with 100% certainty, BUT based on the pictures, I would hypothesize with reasonable certainty that this is most likely mode of failure.

 

That makes sense. Every time an allow flexes it's metallic bonds are torn, over time it's weak enough to fail

 

exactly. It looks like a form of metal fatigue. Just like if you bend a paper clip back and forth enough it breaks pretty easily. But if you try to grab the ends and twist it apart, you won't be able to.

 

now here is my question! knowing that there is a possible defect with the cores (oiling groove) for Cosworth, kelford and GSC and the fact that the FP4R cams have not seen this problem because they have more support around the grooves. who are actually running these cams? i have tried to find some info on them and the only post i have found was from someone who was disappointed with the cams. he complained of rough idle, harder to dial in and the power wasnt there as he expected and as compared to his buddies Cossie setup. now apparently his car along with his buddies car were setup up the same and tuned the same day by the same tuner and the cossies outperformed the FP4R's.
now looking at the specs of the FP4R's they appear to be a 271 with a .440(11.17mm) lift. has anyone else have had any experience with these cams? i would love to upgrade this year and i would like to get a good cam withou having to worry about the cams snapping.

 

I plan on ordereing the intake cam myself if GSC doesnt step up and let me know if my S2 cam is going to be OK. Eating a little bit of power for increased reliability will outweigh the risks.

 

Its difficult to make generalizations when it come to aftermarket cams in Evo's because everybody is running a different setup and with different mods every engine breathes slightly differently. From opinions I have heard on the FP cams, it seems that they are a top quality piece, but both the FP4 and FP5 seem to tend to have a slightly rougher idle and slightly less refined street manners than some of their competitors, but the performance is there (especially at the top end) to make up for it.

That said, based on the info gathered in this thread thus far, only the FP cams have been verified to NOT have the MIVEC groove weakness.

This is a very popular thread that you may or maynot have already seen that shows some baseline comparisons of popular cam choices.

https://www.evolutionm.net/forums/ev...-cam-test.html


keep in mind that even that test is a very rough guideline. How cams perform in each car depends on far too many variables to draw conclusions easily. Best of luck with your decision.

 

I can't tell from the pictures, but is there any chance that the bolt holes may be too shallow? I just got a set of Kelford 280/282...I can't afford another build to find out either.

 

i just bought a set of HKS mivec 272 cams... these havent been reported correct? I was advised that the HKS cams are safe due to them using factory Mitsubishi cores for the mivec cam, thus the reason why they resemble stock (minus the lobes) ??

 

you'll be fine with the HKS cams^.

I think kelford will fix this problem and go to a different core and take a look at their cam design. The cams mentioned in this thread wer popular because they provided good idle,street manners and great power especially kelford. The FP cams are very well made as we expect from FP but the idle is rough and the street manners are livable but not up to par with the kelfords on the other hand you do get the power you want from them.

 

yeah i have seen this thread before. but i can only get a small idea of what to expect since its a built motor, bigger turbo, etc..

each experience is different but it looks like the FP's are known for the rough idle and not as nice street manner.