Here's my thinking: Before we condemn an entire company based on only one known camshaft failure we should:

1. Determine what's the root cause - the core, the stamping, the grinding, some other presently unknown factor

2. Determine if this is an isolated incident, limited to one batch, present in most/signicant number/majority of cams from a certain source

3. Based on the results of those above, was the seller aware of the problem and, if so,
what action did the company take to address the problem

4. Does the company accept responsibility for the manufacturing fault

5. Was the claim settlement satisfactory to the claimant

Jake

 

How'd you find that out? Do you have a photo you can share?

Jake

 

Here are some facts from my understanding of the spring differences on Wayne's setup. The cam that broke has 0.402" lobe lift and he had 1.6 rockers for a total lift of 0.643". The springs on the old edelbrock heads that ran for 30000 miles with no problems with that cam/rockers were 333 lbs/inch with 130 lbs seat pressure. Open pressure with the 1.6 rockers is then (333*.402*1.6)+130 or 344 lb.

With the new AFR heads that have now broken 2 studs and a cam, seat pressure is 155 lb. Spring rate is 428 lb/in, so open pressure is then (428*1.6*.402)+155 or 430 lb.

Question is "how much spring pressure can a cast core hydraulic roller cam handle if it's run to 6400 RPM?"

 

Are the springs binding, or is the retainer hitting the top of the valve guide by any chance?

 

With a new cam being in the motor there is no way to tell what had happened, but I just rolled the engine with the cam and it is nowhere close to the top of the guide.

The 2nd question is could the AFR springs where the seat pressure is 155 lb. Spring rate is 428 lb/in, so open pressure is then (428*1.6*.402)+155 or 430 lb break a cam?

 

At least Crane was straightforward with this guy and they asked to see his old one.

http://www.chevelles.com/forums/show...=1#post2972805

 

http://cranecams.com/?show=article&id=14

That open pressure sounds a little much to me, you may want to ask the question on the speedtalk.com forums

 

Back in the 80's I managed a shop that did Nascar stuff and we never ran a cast cam or 3/8 studs with that sort of spring pressure. Similar lift back then and 7000 to 7500 rpm. You have to remember that the higher the rocker ratio the greater the load on the cam.
Dave

 

Just spent a considerable amount of time on the phone with Crower. They strongly suggested that the spring rates from the AFR springs were too stong and that with that amount of spring rate that there could be problems with the lifters not pumping up properly at higher RPMS. I have ordered the Springs recommended for my new cam. I also asked them if the AFR springs could break a cam and they said no way!! So new springs matched to the cam and lifters. All should be good in performance town.....(just got a brand new motor I wasn't planing on buying, bye, bye Xmas)

 

It sounds like you covered all your bases. I know what you mean about the unexpected new motors, hopefully its performance will make you believe it was money well spent.

 

have you guys verified whether or not that was a CC cast iron roller? The pics look like cast iron, but the part number posted didn't end in -8?

The one being discussed now at chevelles.com is broken off at the stub where the iron gear presses on.

Whatta classic CC deal, blaming the engine design. Hey, if the caller buys it, hangs up, they're off the phone and off the hook.

Tom Mobley @ chevelles.com

 

It was a cast cam part number 12-xxxx-8.

I had the part examined today. We verified it was fatigue and found there was no defect in the cam. The cast-in "D" mark was actually the area that held on until the end, as that portion was the last portion of the cross section to fail in overstress. It was the opposite side of the "D" where the fatigue cracks nucleated after which they propagated toward the "D".

So the cam failed due to overloading. Now what caused the overload is debatable, but the crack could have started by several things including an overrev, too stiff of springs with too much lift, lifters that weren't pumped up, engine dynamics, spring surge, etc. If the springs were so strong that they took up most of the strength margin of the cam material, then any of these other items could pushed the stress over the edge and got the crack started. After the crack started the margin of safety could have been negative and the crack would have propagated from there just under normal driving, at which point it could have failed idling in the driveway.

Makes me wonder what springs I have in my heads with my 3/8 studs and 1.65 rockers...

 

155/430 is not a big deal unless the cam is made of wood or something. Do you guys have access to a hardness tester? come up with a Brinnell or Rockwell number?

 

Could you let us know your justification for the statement that 430 is not pushing the limits of a cast cam with 0.64" lift? We've had other experts say that they were not comfortable with those numbers.

I could probably get a Rockwell number from the cross section where it was cut to fit in the scope. What Rockwell number/material strength are you thinking a cast heat treated cam should be?

 

My opinion on the 155/430 deal is based on 30 years experience with roller cams. IMO all the cast rollers are junk, an accident waiting to happen. As far as CC is concerned, looks to me like they use some kind of business methods based deal on this stuff. As in, if the returns don't start eating up more than some xx% of the profits then it's OK. The value of xx is based on whatever thresholds they're comfortable with. Their attitude towards their customers is typified, IMO, by them being OK with their call center CSRs blaming the failures on the design of the engine. Like SBs having a well-known history of breaking cams? Only CC cast iron rollers AFAIK. Since 1955 anyway? maybe before that there were lots of cam problems.

On the numbers, I have access to an engineer at a well known California cam company that has a excellent reputation for quality products. He doesn't BS me. Problem is it's hard to find CC victi....ah, customers who actually can accomplish getting this stuff tested.

What did the bearings on either side of the break look like? Any signs of excessive wear that might have left the cam unsupported, setting it up for a catastrophic failure?

 

The bearings were bad, my machine shop guy wondered the same thing, wondering if the cam might be unsupported.

 

how were they bad? recent damage for the disaster doesn't count.

 

Give Tom a chance, guy really knows his stuff and shares freely over at TC maybe he can help a few out here also.



67T56Elky

 

67T56Elky, That's really nice of you. I've been on Chevelles.com so long and wrote so much I sort of forget when I go someplace where I'm unknown. "Who is that jerk and what is he doing posting here anyway?"

I think the guys in this thread figured out that I'm not real enthused about CC and their cruddy parts and even cruddier business practices.

Thanks again for your kind words.

Tom <<AKA "innernetinjuneggspurt" >>

 

I don't think you're a jerk, but, just to even things out, I hold the opposite view of CompCams.

I've been dealing with them since they first opened their doors and, considering all the race engine and street engine parts I've bought, I don't have any complaint.

Jake