denver

iTrader: (9)

Kelford changed their core, read above.
I think you would be ok to buy them now. They added a radius in the oiling groves and decreased the depth, thus increasing the material at the groves. Just check to make sure they are the new core.

JDMevoBOOST

iTrader: (37)

How do you snap an intake cam and not screw anything else up? Did you shut the car down like immediately? Or did the car turn itself off?

NWM_Tech

"could have" but most likely it's the design. Why else would they change the radius and depth of the Mivec oiling groove?

R/TErnie

iTrader: (32)

To improve the strength of the camshafts regardless the cause. I'm sure there is a reason why these camshafts are failing. No one quite knows yet, but making them stronger won't necessarily fix the problem. The problem lies within what is actually happening to generate enough force to fail the camshafts. It takes a STAGGERING amount of force to fail these bumpsticks...something is amiss.

SRT-TO-EVO

iTrader: (12)

I'm going to disagree here, unless someone can explain where these "staggering" forces within the motor are coming from. Let's also remember NOT ONE FP core has failed to date, so that pretty much ends this debate.

drb

iTrader: (39)

I agree. It certainly looks like their were some issues with these cams. Hopefully the manufacturers will step up and at least replace the broken cams with a better design.

Dan (drb)

MattyBoyMR

iTrader: (21)

when my cam shaft broke...my car just shut off...and nothing got messed up....and i runs like a beast now...lol

Peteypab2133

iTrader: (27)

Mine also just shut of instantly, and made NO SOUNDS at all. Had NO idea what happened when it first happened. All of the intake valves were bent, and was an easy fix.

NWM_Tech

balderdash

I don't think there's much mystery here. Camshafts have been made for years without catastrophic failure problems. They don't just break for reasons that "no one quite knows".

The factory adds double the weight at the sprocket with this early Mivec setup, out on the end where it has the most leverage. AND at the same time they reduce the section dia right behind the sprocket with grooves to supply oil to the same setup, right at the weakest place structurally. This design is sort of flawed because usually the factory setup is overbuilt. (This is confirmed by the 4B11 which has a larger section dia on the area in question.) In this early Mivec case it's not a big problem for the factory because while it is marginal it's strong enough for the stock setup, IOW stock cams aren't breaking.

So the original factory design is inherently weak but adequate for stock purposes.

Now we have some AM perf cams breaking, but the stock cams don't break. So what is the difference between AM and stock?

Only 2 possibilities, design flaw/flaws, installation problems.

First let's look at the history of AM design. The AM knows the factories, especially the Japanese, overbuilds and they rely on that. Cases in point would be things like cranks, rods, cams etc. You can put some power adders and you don't necessarily have to beef up the entire motor, because it's assumed that the factory has overbuilt by a factor of 2 or 3(?). Bigger turbo, stock crank, no problem because there's a design margin. You can put bigger lobes and run stiffer springs with the same base factory cam design because it's usually overbuilt in the first place. BUT in this case the factory failed to design overbuild into this cam for reasons already discussed.

Some have said it's install problems. Don't think that's too likely because that almost always leaves signs of which there have been none so far shown. Like stretched/stripped threads or impact damage from loose parts. And there's been no history of this happening at this rate with other AM cams in the past.

Even with the mostly out of focus pics of the AM perf cams it's pretty apparent that the oiling grooves are deeper, less radiused, and have machining score/galling marks. There's also been measurements posted that confirm the section dia and radius is less than stock. Any one of these three factors can cause added weakness to an already weak design. On top of that the added stresses of higher performance and you're over the edge of failure.

The reason that you won't see failure without "staggering forces" when testing new cams is that it's either a cyclic/harmonic problem or a machining score-galling/crack propagation problem. IOW it takes some time of real world usage before failure, and just like a dyno the real world is not exactly like a test.

In response the out-standing manufactures that care have come out with a updated design that addresses all three weakening factors. Just the fact this has been done is an indicator the original AM design had a problem, you don't knowingly release something in the first place if it's going to break. And you don't normally spend more money updating a design after a bunch of units have already sold without problem. Neither of these are good for business.

It's curious we haven't heard back with conclusive results of inspected failed cams (unless I've missed some posts). Seems like maybe a cautious approach, although the real thing that matters, the supply of updated cams is being taken care of. It would seem more info would be better for the future, like betting this mistake won't happen again, which saves the AM guys too.

This conjecture/theory is all based on some mediocre pics and spotty posts of a few measurements. If anyone really cares to put this thing to rest for good they need to measure with a digital caliper and take some really good super micro pics (focusing on the bottom of the groove) of 3 different cams.

A. stock intake cam
B. AM perf cam that is failing
C. updated AM perf cam

1. measure section dia at bottom of mivec oiling grooves
2. measure groove radius
3. super micro photo of oiling groove surface finish

This should be right up some EVO fan's alley, being we are a fanatical bunch and usually interested/involved in the technical aspect of this awesome beast.

would do it myself but no access to all the cams in question

lst4g63

iTrader: (2)

Just thought I'd give an update since I took my valve cover off....

I have/had cossi M2's that snapped,

Bath JGR6

R/TErnie

iTrader: (32)

If you don't know what is causing the problem, how do you plan on fixing it.

Find the problem the solution will follow.

I'll be doing some analysis of a broken cam in the following weeks. I'll let you know what I find.

gamebred26

iTrader: (19)

this is ****ing really disappointing...i have m2's and just spent a good amount of money building my motor and have to worry about this ****.

GPTourer

What is it about an AM cam that means more stress will be put on it in this area? I understand the need to beef up a drivetrain for higher revving reasons, but that means better/stronger springs and retainers, but how is that putting stress on the ends of the cam where the MIVEC groove is?

gamebred26

iTrader: (19)

is there a list of how manyfrom each manufacturer that has snapped?

if not someone should make one.

KevinD

iTrader: (56)

the cam has a torque stress on it along the entire length of the stick. this load is small at the very end (cylinder 4 valve #2). because the only load is the torque caused by the spring/rocker/lobe force causing the cam to twist. there is also a vertical force component, but there are bearings between each cylinder effectively limiting any forces from one end to the other.

now, the cam inside of the second lobe (cylinder 4 valve #1) is going to feel a torque from both C4V1 and C4V2. this continues all the way in, to the MIVEC groves where the torque is going to be the highest. this is where the cam gear (the opposing torque), and all the torques from all the valves are summed at. this point also has a bending force because the gear overhangs off the head.

essentially the loads are absolutely the highest at this point, and any and all stress risers in the material at the MIVEC groove are going to weaken it dramatically when only given a certain cross section you can work with.