Technical BBC new camshaft failure (long story)

This somewhat of a long story, hopefully it will save you guys some problems when you put a cam in, and maybe someone has a good reason where we or the cam went wrong.

Well after almost two dozen or more new flat tappet cam installs over the years, not including roller cams, I now have one that failed during break in.

Engine background. 454, what’s been done to the inside of the engine is unknown, if anything other than an older cam install. The owner of the car works for me and does not have any past history on the engine, other than he has owned it for many years. He didn’t really know it had a aftermarket cam in it, but suspected it.

The engine had a somewhat mild older Crane cam roughly .500 lift, and had the distributor shaft wear out the housing and was losing timing and Dwell was varying. Car was still running before disassembly, but poorly.

The distributor was a old GM iron housing with points ignition. The distributor gear was heavily worn and so was the camshaft distributor gear. This is why the cam was removed and replaced.

Lobes and lifters of the original cam appeared to be fine with no or minimal wear, and the engine oil was not nasty dirty and internally looked pretty decent.

So we chose to replace the cam with another Crane cam and lifters of the same part number that was in it. We assume the valve springs are correct for the cam that was in it, since it had no appreciable wear on the lifters or lobes. Had to call Crane, to cross reference the old part number on the cam to a new part number.

We installed the new cam with all the normal procedures. Cam break in lube, soaked the lifters in oil, installed a Cloyes street true roller timing chain and gears, found true TDC, degreed the cam, adjusted the valves the TDC-90*-180*-270* method as it has a fully degreed balancer, checked to make sure the stamped steel rockers had sufficient clearance between the stud, added more cam break in lube to the cam before the intake was reinstalled. The distributor was replaced with a MSD ready to run with the proper curve put in it.

Engine oil and filter were replaced with a AC1218 Filter and Penn Grade break in oil.

So where everything went to hell in a hand basket was during break in.

Engine started rather quickly and RPM was brought up to around 2300-2500 right away.

RPM was varied somewhat between 2300-2800.

Oil pressure was at 50PSI.

At around 10 minutes into it the engine started to change tone and at 15 minutes we shut it off, said there is something wrong. Car is pretty loud so hearing noise is pretty hard. Let it cool down and restarted it at a lower rpm to hear noise and there was valve clatter in the left valve cover.

Pulled the valve cover and found intake 5 and exhaust 7 had lots of slop.

Ran the engine with the valve cover off and all rockers were oiling good and could see those two were the issue.

First thing we checked was to make sure the rocker arm was not bottoming out on the stud. We could not see any evidence of that, push rods fine.

Pulled the cam back out of it and found those two lobes and lifters wiped out.

In 40 years of business, I have never seen a cam go flat like this one. The two lifters look like someone went at them on a bench grinder and two lobes on the cam are wiped out. All other lobes and the lobe between the two and lifters still look good. The Parkerizing is still on all the other lobes.

Talked to Crane and they said, you didn’t break it in right, Penn Grade break in oil is no good anymore, RPM shouldn’t have been below 2500, our product couldn’t be bad etc. bullshit.

Now, as far as I am concerned there is so much metal in the engine, its got to come apart.

This ain’t my first rodeo installing a cam, so where did we go wrong?

Worst part is we will probably never know why it failed.

I also talked with a Buddy of mine that is was GM engineer, that was inv olved with the camshaft failures in the 1980s that GM had. He think the heat treat on the lobes is suspect, I think possibly two (soft?) bad lifters. But I just don’t know.

This is what he had to say.
Flat Tappet Cams are not as good for durability as rollers for one reason the Roller cam blanks are steal while the flat tappet are made of iron castings. The iron camshaft blanks could not handle the contact stresses at the roller interface. people talk about Hertzian stresses which is just a way to calculate contact stresses at a curved interface. So industry bit the bullet and went to steel for roller cams. Back to Flat tappet cams, the endurance limit for iron cams is complex and depends on the iron chemistry, surface hardness and depth of hardness. GM flat tappet production engines had issues with wiping cam lobes. I have first hand experienced this in the Small Block group and the Iron Duke group. sometimes it could be blamed on the lifter bores not oriented correctly to the camshaft do to bad block machining but most of the time the cause was improper heat treatment of the lobes. Or at least that is how we closed the cases. Like the pictures show all the evidence is gone relative to heat treat so its nearly impossible to do any rudimentary checks to prove heat treat issues with this camshaft. The reality is that iron flat tappet cams are very marginal for load carrying capability, and variation in chemistry, heat treat surface finish, and block machining will effect the observed endurance limit. I suppose people hope running a break in procedure will help by improving the surface finish of the two mating parts before you expose them to higher loading. I never have understood why the Hertzian contact stresses increase somewhat as the engine speed decreases approaching idle, generally it increases as the speed increases this phenomenon has been well documented. So that is why people believe breaking in at a speed above idle is required. You are tryin to find the operating point of lowest contact stresses and let the parts rub together to improve surface finish and give a marginal system better chance of surviving. That all said my bets are the camshaft lobe in this engine heat treat was less than optimal, but we can never prove it with the parts in hand.

Here are photos for your viewing pleasure

Bill

 

wow

 

Wow!

 

WOW!

 

Well, i've always understood that the reason for an elevated break in RPM was to ensure that plenty of oil was flying around as that's all that lubes the cam/lifter interface. That's neither here nor there in this case since you did it properly. I would have to suspect improperly made lifters as their seem to be a lot of flat tappet failures of late. The removal of zinc hasn't helped any. If your lifters came from Crane it would be interesting to see where they sourced them.

 

i have never seen anything like that. Obvious the lifters were not spinning. Why? Who knows. Hope you figure it out. I would put a lifter in suspicious holes and see if you can make them spin by hand. Maybe something in the lifter bores prevented them from spinning.

 

Mechanical failure nothing you did


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WOWeeezy .

 

Thats pretty crazy. Looks like you took the parts to a bench grinder!

 

Yikes! That Hurts just to look at it!

 

I've lost a few on BBCs over the years, it sucks....

I've gone to rollers on them now.

 

Having been in the cam business since 1953, I have seen lobes and lifters like that hundreds of times and from all brands of engines. There are many causes and most of the time it can't be pin pointed because the evidence is destroyed. The problem is not new. In 1956 Ford came out with a factory bulletin saying they expected in excess of
2 % of all 312 Y block cams to fail in the first 200 miles. That turned out to be a very conservative estimate.

 

Mistake #1, you didn't take the lifters apart and clean them out. I have found everything but the kitchen sink inside brand new lifters over the years...

Mistake #2 Brad Penn oil is garbage..

I always screw studs into the valve cover bolt holes so I can lift the valve covers off and watch to see the push rods spinning. If there not shut it off..

You never had a chance with that weak steel, that cam and lifters looks like it was made from Crayon!!

 

On the re-rebuild use low pressure valve springs for break in,and add a Zinc additive to Valvoline racing oil.After you have several hundred miles,and everything is seated replace the valve springs with stronger ones.My next engine will be a roller for just this reason.The lifters cost way more up front,but it saves having to do a re-rebuild.

 

Would have been very simple for Crane to send you a new cam and lifters. Would have cost them maybe $100? But now we have dozens of people who will never buy a Crane cam.

 

Question about cam lobes I've always wondered, and will explain first. Way back when in a JC class, we had a hardness tester, it dropped a "point" to the metal, and gave a result of hardness. Now, "way back when" I was just following along, but I wonder if you did a hardness test on cam lobes, say they all came out good-(whatever that spec should be)-would doing the test compromise the lobe in anyway?

 

Lifters arent what they use to be.They die first,and take the cam/engine with it.

 

SO you think the issue is with the lifters, not the cam? I don't know, why I'm asking. So if I were to take a hardness test on lifters then, would that test compromise the lifter?

 

Excellent presentation !!!!
My suspicion is that the lifters weren't rotating. If they were, the wear would seem to have made the end of the lifter sharp like the end of a pencil instead of just a wedge shape. I think maybe minor tolerance difference in the machined surfaces of the lifters AND the lifter bores may have been coked up slightly allowing the lifter to slip in place but keep it from rotating. I personally think that running a small ball hone thru each lifter bore prior to replacing lifters is a good practice and think that its the cause of many lifter failures. Its odd that almost all cam failures only involve one or two cam lobes, which makes me believe that the cams are ok, or the manufacturers would improve their process. It just seems illogical that ALL cam manufacturers would have a heat treatment problem. It does seem more logical that whatever causes these issues is something that is beyond the manufacters control or they would fix it. So the thing that is beyond their control is the surfaces the parts interact with in the engine. One of those is lifter bores.
Anyway, thats my best guess with absolutely nothing to substantiate it. Sorry you have to go thru this..........

 

Holy Toledo! I’ve seen lots of flat cams in my time, but that is the worst. I know that Crane went belly up a few years ago, S&S Cycle bought their Harley parts line, who owns them now? I’ve had good luck with Crane stuff, but that was 25 years ago. I sure understand about the lifters not rotating, and it may very well be the cause, but it sure seems like there are a lot of this lately. Excellent presentation, thanks for the information. I don’t have any engine projects on the horizon, but the next one will definitely be a roller. I know that lots of people say it’s the oil’s fault, but I’ve always used 15w-40 of several different brands and never lost a camshaft. Even back when I was racing, we didn’t even consider using lighter springs, we were kids, what the hell did we know?, and never lost a cam. By the way, I won’t buy anything from Crane anymore either.


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Gruesome.

Is it possible that the face of the lifters being worn at such an obvious angle is a result of the lifters not rotating properly in their bore? Would a light honing of the lifter bores possibly made a difference?

 

I agree that honing the lifter bores is a good idea, but it’s kind of tough to do on an assembled engine. Where does the honing grit go?


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I would blame the lifters.

 

The way I understand it, most if not all cam cores are outsourced from only a few companies that cast the cores and the heat treat is done before the lobes are ground.

Don't know if the Parkerizing is done by Crane or not.

I would venture to bet that Crane did not manufacture the lifters and are outsourced.

You probably can't see it in the photos I uploaded due to me resizing them.
I have a camera with quite high resolution and when looking at the photos of one of the ok lifters, on my computer screen, and enlarge the photo, I can see what looks like tiny pinholes in the face of the lifter. Almost looks like the surface is porius.
Don't know if I am looking at something or nothing?

Bill

 

Actually Summit has offered to replace the cam and lifters one time. They offered to replace with a comparable Lunati cam and lifters free of charge. Why Lunati, I don't know. I would take a Lunati any day over a Crane.
I am afraid with all the metal in the engine now, the bearings will be short lived if put back together without complete disassembly.

Bill

 

True, dat!

But mainly I was wondering if something like that might have been what caused this whole job to go south.

 

That is pretty ugly. For sure the lifters were not rotating. The key question is why. I think you did everything right, so best guess is bad parts.

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I like Lunati, if Summit are offering this there is definate3ly a reason, good for them. Totally tear it down and tank it with new bearings if the bores look good.

 

Obviously it's a lot easier if someone is doing a rebuild and has the engine apart. Someone doing just a cam replacement would have to take precautions to prevent the grit from falling into the engine. Some carefully positioned rags or some kind of sheet metal catch tray and careful work should preclude contamination. Then wipe with some carb cleaner and white rags. It shouldn't really take much to clear any coke from the bores.

 

I was over thinking the honing process. You mentioned honing and I automatically thought like cylinder honing. As soon as you said Coke, the dim bulb in my head fizzled on. You are right, it would not take much at all, just a few quick swipes. Thanks for making me think a little harder about this.


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