Tex71BB

Sheds a little light on why so many guys are experiencing wiped lobes.

From: http://www.nastyz28.com/ubb/Forum8/HTML/008332.html

"For those that don't feel like plowing through 4 pages of replies from the other thread about this here's the Reader's Digest version....
I had a new Comp Cams XE282S flat tappet cam and fresh lifters mysteriously destroy themselves shortly after installation- wiped lobes everywhere. A post-mortem revealed nothing to point to a problem with installation or break-in procedure. A First for me in almost 20 years.

This got me seriously irked. I needed CLOSURE. I had to KNOW. A Pit Bull with a T-Bone. I couldn't let it go.

Bob (1978LT) was kind enough to offer to Rockwell hardness test the old cam and lifters to see if that revelaed anything weird. It did.

Here's what the dead cam and lifters tested at:

Good lifter: 51-52 Rockwell
Damaged lifter: 47-48 Rockwell
Camshaft: 26-28 Rockwell

Here's what a cam and lifter set SHOULD test at (provided by OldSStroker from Camaroz28.com in the advanced tech section):

Lifters: ~60
Cam: mid 50s

Notice something odd? Yep, the cam is too soft. WAY WAY too soft. The lifters are maybe a smidge low, but the cam is off the bottom end of the scale.

Ladies and gents, we got a cam that never got properly hardened. Period. Bad product.

I only feel mildly better now. You can probably guess why."

gerry72

It's missing some info that I have to wonder about. The cam is surface hardned after it is ground. If the lobe gets wiped, the treatment is destroyed and doing a Rockwell under these conditions would not tell you what the hardness was "as shipped." I'd like to see the numbers on a new, unused cam.

I don't doubt that there is something going on with CC since, despite all the cautions and warnings about break-in, you have to do some serious wrong to take out a cam.

norvalwilhelm

I spent the morning tearing a brand new 3800 V6 down to demonstrate the internals of a motor for my engineering class.
As soon as I read this post I grabbed the roller cam out of the motor and did a rockwell hardness test on it and got a low of 46 and a high of 49RC.
Cams are alot softer then you think. I cut up the cam with a normal cut off saw. The lobes are induction hardened.

ddecart

My thoughts exactly Gerry. Testing the core material and not the hardened material isn't going to tell much at all.

Tex71BB

The tester says he tested on an undamaged part of the cam, but we don't know what part that was.

The Money Pit

I wiped a lobe on my XE-274 in the first 2000 miles,tore it down and replaced with a yet bigger cam(Xe-284),but broke it in with 1.5 rockers and switched to 1.60 later.Long story short,I never wiped a lobe before in my life,and I've built a lot of engines.The machinist I had cook the block has been doing engines for half a century,and he said sometimes it just happens,with no explaination.Put a new cam in and forget it.If Comp Cams is making inferior product,why are so many buildups using them?

MotorHead

:iagree: The machinist who gets my business uses nothing but CC cams ( unless the customer specifies different) If he thought the cams were a problem he would not use them :D

lil ski

If you harden a shaft it should be the same hardness through out ,high heat will change the hardness some. Im not sure but maybe a cam shaft is case hardned. Testing it on any undamaged part should give you the hardness it was treated to.

lostpatrolman

It was my understanding that basically all cam companies use the same producer for the blank cam, then just cut it to their specs. Does comp cams make their own blanks then machine them to specs?

Gordonm

You can definitly just harden the outer couple of thousandths on a cam. Why harden the whole cam when you only need to case harden the material. I have seen mony wheels that have been case hardened for machinery. When the case hardening is gone the inner is soft. It may have been a bad cam blank or maybe a lobe was not hardened correctly. Comp Cams would not be as big or racers would not use them if they were making poor products.

Brown78

:mad Last year took the trip to Bowling Green for the 50th. Brand new engine with a Comp Cam. Good thing I have a friend in KY. Because, my new engine had a bad cam. When he took it out it had 2 round lobes. There was only about 2000 miles on that engine. After that the it became a bad luck engine. Now it's collecting dust in a corner. :mad

SteveG75

Well, I had to XE flat tappet cams wipe. The 262 lasted 5000 miles and the 274 less than 200.

New cam is a hyd roller setup so hopefully, that problem is solved. I did go with Crane as well but that decision was laso motivated by the wider LSA and later intake closing which will help tame my 10:1 compression a little by reducing the DCR (dynamic compression ratio).

comp

HAS anyone contacted C. Cam's about this ??? what did they say hardness
should be ???? I'd think ( :lolg: ) the cam should be close to the same as the
lifter not as hard but not that far off :confused:

The Dude

This is correct. As far as I know there are only two or three cam blank manufacturers and the grinders (Comp, Lunati, Crane, etc.) will cut them to their own specs.

PureSilver

Was engine assumbly done with cam lube? Was the engine 'prelubed' by pulling the distributor and running the oil pump? Were all the lashes set correctly? Too much pump up in a lifter creates some friction...

Turbo-Jet

only the surface of camshaft lobes are hardened because you don't want the shaft body and core to be too brittle.

testing rests: what scale are these? (assume C?) I think testing is only valid if done on an unused cam lobe.

a general rule for a pair of load bearing parts is that one material must be quite softer and more elastic than the other. after break-in, point contact stress are managed by the softer material yielding slightly to increase area. lifters are HARD. cam is softer. i would look into surface finish and geometry too. It is probably unlikely that q/c from a big company would let a bad part out the door, but you never know until it is too late...

Freepop

The hardness test may not be valid for several reasons.
1. As others have said, the hardened material may be gone.
2. The depth of hardness may not be sufficient to be able to check on a Rockwell tester. You have to use a surface type checker, the name illudes me at the moment.

If it was induction hardened (which is a surface hardening), you can selectively target to specific areas and omit others within 1/16 or so of an inch, quite easily.
Also, I doubt that it was through hardened, because straightness becomes a problem with profiles such as a cam

I agree with Turbo-Jet on the difference in hardness of materials.


[Modified by Freepop, 10:39 AM 5/7/2004]


[Modified by Freepop, 10:40 AM 5/7/2004]

lostpatrolman

I understand your guys arguments about not being able to accurately test a wiped out lobe becuase the case hardening is now gone, but about about the rest of the initial discussion??
Supposedly the cam itself was way too soft, and the other undamaged lobes are also on the soft side.

70 LS1

So was this a bad batch or are all of comps cams soft? I am getting ready to buy a cam and nearly all of the LS1 cams are custom ground Comps. I guess softness isn't as important for a roller setup, but I don't want to buy junk.

BSeery

:iagree: