i don't typically chime in on things, but i will. I built the motor for this car. i have NEVER, and WILL NEVER install cam bolts with an impact gun. that is both careless and irresponsible. everything is torqued according to their specs, by hand, and by a calibrated torque wrench. i have only heard of one other HR cam breaking in the same manner as this, and it was on a stock motor (i.e. never opened up) running a greddy twin setup pushing 500+ wheel hp. my concern is perhaps the BC cam spring combo may be too stiff for stock cams to handle? i used to have this same issue in the late 90s/early 2000's with the original crower springs for hondas. they were too stiff for most cams and would crack the cam, too.

at the time, that was uncommon, too, but as the customer base started to all use the same gamut of parts, the problem became more apparent. this, too, may be the case. these motors are still fairly 'new' for modifying, so we may not be finding installation error, but rather engineering defects in the products.

i hope to hear back soon as to what caused this break, or maybe some form of tell-tale sign of cause. as for 'troublesome builds', for every one person that may voice out over some issue they found unsatisfactory, there are a far greater more people out there extremely happy. so happy, in fact, that they are too busy out enjoying their cars instead of typing up positive reviews on message boards for all to read.

i stand by my motor builds 100%. i have ALWAYS offered my own personal guarantee (outside of S&R and anywhere else), that i will PERSONALLY hold myself accountable for any mistake that i may make on my engine builds. This means, that if i built your motor, i will warranty it against my own errors for as long as you own it. who else does this? luckily, in the 11+ years or so that i have been building motors, i have never had to use this guarantee. why? because i take my time, and assemble these with care and precision.

oil lines will leak, turbos go bad, rubber gaskets may seep, blah blah. but i know that inside that (and any) motor, it was built with longevity in mind and i take my own work extremely personal. motor assembly is a reflection on me as a builder; not as an employee of any business.

 

The metal fatigue that a cam experiences should be directly related to the resistance to turning, not the wtq of the crank (which would far exceed the former). I don't understand why resistance would suddenly increase. I do think it's possible for the cam to fail prematurely but after an extended period because of increased resistance right from the time of install (for whatever reason) since metal fatigue is cumulative. A one off weak cam or some other underlying problem resulting in increased resistance in the valve train? That's the question I'd be digging to get answers to. Maybe there's some way to test valve train resistance manually after reinstall?

EDIT: Durdan, since you chimed in (and as a novice seeking clarification), is it possible to adjust torque specs to decrease valvetrain resistance - or is that solely going to be a function of the springs and cam lobes themselves?

 

OP do you have any pics of the cam?

 

Some people are too busy pointing fingers OR think they know more than the people that have been doing this for decades. They don't take the time to try and find all the reasons that could have caused the failure and start narrowing them down. Guess that just takes too much energy............

 

the torque specs are generally delineated by the hardware. fastening the cam gear to the cam would bear no change given a different spring combo. the force of the lobe required to push down on a tighter spring calls for a stronger material in the cam itself. the gear is merely on the end. BUT, what one must be able to comprehend is, the crank is turning a chain. that chain is acting upon the intake cam directly. from there, the exhaust cam is linked to the intake cam by a secondary chain. if the crankshaft is turning with a much greater force now (given the substantial amount of torque over stock) and at a much higher rate of acceleration (horsepower is the result of a mathematical equation of torque vs RPM vs a given time frame; in laymen's terms), i could see that there is the propensity to literally sheer off the face of a cam. if that cam is harder to spin over due to having to act upon a stiffer spring set, and if that crank is trying to rotate that cam with a MUCH greater force, issues may arise. Remember, crank shafts on these cars are forged. it's not snapping before a cam does. Cams are essentially cast iron 'pot metal'. hell, you can bust a cam in half by cracking over the top of a bench vise.

 

they r at the shop now as we speak taking it out

 

Wouldn't a stuck closed valve cause this?

 

that would be a stretch to cause. that would cause a localized force being presented against the cam, and typically (bearing the actual structural integrity of the cam), you should see the break AT that lobe. this, too, has happened on other cars that i have seen in the past. for a cam to break at the front such as this, it is either portraying a fault in the casting of the cam itself, or an over all force against all the lobes (i.e. all springs too stiff) which then leads to a break in the one weak spot of the cam design.

this is all still conjecture, though. until i see the actual part, we can all play the guessing game. i just tend to look at things from an engineering perspective.

 

I also know someone who installed a cam shaft with an impact wrench and it failed him as well. Not long after he installed it actually. Also a DE and was making 700+WHP ( forget exact number ) and running 10sec 1/4miles. I do not remember which cam it was but I am 100% sure he blamed it on him using an impact gun to get it done and not on the cam it self.

 

That's not what happened here though. No impact gun was used.

 

Do you have proof? Were you there when they put it in? Everyone can swear it was or wasn't. Only person/people that will know the truth are the guy(s) that were there doing the installing / building.

 

well, since i am the one that built it, i can say for certain i did not do that. i admit when i make mistakes and you know what, **** happens sometimes. and when/if i DO make a mistake, i own it. i admit it, i fix it, and i pay for it out of pocket. it happens VERY infrequently, but we are all human after all.

but no, i did not use an impact gun on this, or any other, cam. i am not an idiot and have been building motors for quite a long time.

 

local post about subject :

http://forums.350zclubofflorida.net/...ead.php?t=5207

 

great way to stir the pot there, buddy. if you notice, this thread is nothing but educational posts and reasoning. what benefit is there to bring quarrels into it?

 

Can someone explain how/why using an impact gun causes problems exactly? I am missing why it matters how tightly bound the cam gear is to the cam. Not trying to stir the pot, just trying to learn...

 

it's not so much the torque numbers (numbers DO matter, but that's besides the point) but rather the action in which those numbers are achieved. the constant battering of an impact gun can weaken and fatigue the metal very quickly; thereby causing strength issues.

 

Gotcha. Thanks. Too bad that part of the cam is not reinforced...

 

well, it's more so the type of metal used, as opposed to the shape of the cam end itself. cast iron, while very strong, is very brittle. meaning, where a malleable metal is "weaker", when you approach that point, it fatigues and bends. Brittle metals can take more abuse, but when you reach their point, instead of bending, they crack and sheer.

 

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well, that's exactly what he means by unresolved. since it's a thread about this same car, i highly think it bears repeating.

also, the issues he states in that thread were resolved, what... a year or two ago?