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JPhil 09-17-2005 06:54 PM

Questions for wiped lobe victims & engine gurus

What were your cam specs (adv. dur., .050 dur., valve lift)?
Was it the intake or exhaust lobe that wiped?

I've been doing some research & figuring...I'm not an experienced engine builder by any means, so if you think I'm barking up the wrong tree, please say so, and why.

I've made a list of a number of cams & specs from a number of manufacturers and used two formulae to try to come up with a "performance vs. reliability" factor. One is ".050 duration divided by valve lift should equal 47.5% or greater" which I saw here (sorry, cannot remember when or who, but thanks). Let's call it the "X factor".
The other is my own creation, "Advertised duration minus .050 duration", or "Y factor".
I realize I do not know where the adv. duration is taken from--.002, .006, or wherever. But that's what's published, that's what I used.

My theory: Both are ways to guage the steepness of the lobe ramp, which determines the stresses on the lifter & lobe, which has an effect on the reliability & longevity of the 'interface'.
Still with me? Here are a few samples:


cr 272H10 272 216 .454 47.6 56
cc HE268H 268 218 .454 48 50
cc XE262H 262/270 218/224 464/470 46.9/47.6 44/46
cc XE268H 268/280 224/230 477/480 46.9/47.9 44/50
lun 60101 256/262 213/219 454/468 46.9/46.8 43/43
chev L82 272/288 224/224 450/460 49.7/48.7 48/64

I know there are other factors to be considered,and with my inexperience I do not necessarily know what they are. But I believe I see a correlation: The the lower the X & Y factors, the lower the reliability....
Does this seem to have any merit? Or is it B.S.?
Comments and thoughts requested and welcomed.


well, ding dang it all! I spent a long time getting those numbers into nice neat columns but I can't make 'em stay that way!!! Sorry I guess you all will have to try to sort 'em out. S**t!

-------------------------------------------------------------------------- 09-17-2005 07:54 PM

Other factors are important also. Valve spring pressures have great importance. Along with proper clearances in the valve train. Lifter types also can determine wear characteristics. Proper break in is the next big thing.

MOST wiped lobes I have seen on aftermkt cams in the last forty plus years of building are caused by the installer!! (yes! I have lost a couple myself)

As a matter of fact. Just yesterday I was called to do a check out on an Isky. The owners were experianced circle track guys.

But, here was the scenerio. They had no idea what kind of spring pressure they had. The aluminum roller rockers were binding on he valve retainers. They had an earlytiming set in a late model block and the poor double roller Cloyes had milled the center block oiling boss back at least 3/8".

The cam was too far forward when assembled because of the improper timing set. Lifters no rotate,, lifters wipe out cam..

You will notice that long gentle moderate lifts (most factory cams) promote long life. But if everything is not correct in the engine they will not last.

bracketeer 09-18-2005 01:17 AM

I wiped out my first cam a couple of weeks ago. I took out #4 and #8 exhaust. Installed in a 400 sb. Cam specs can be found here. The engine was not built by the machine shop. The cam was broken in for me by an experienced High Performance engine builder. All parts were new, engine was line honed, parallel decked, torque plate honed, balanced with ring gear and balancer. After disassembly we took the parts to the machine shop for their opinion. They said, that their cam failure rate has gone up 300% in the past 3 yrs. They blame it on poor quality control on lifters. According to them, lifters diameter specs have declined in recent yrs.

k-star 09-19-2005 08:28 AM

IMO, there is just way to many factors to ever come up with a set answer..

Even if you would say that one out of 10 cams with X duration or with a factor y of such and such would wipe a lobe how would you ever know if the cam you installed was the 1st or the 10th cam?????

The biggest problem is with pin pointing what cause the failure... So if you blame 5 cams with x numbers for having failures and all 5 were caused by improper break-in all that data is flawed.....

The only way i could see collecting usable data is to do it all in controlled conditions... my guess would be that in controlled conditions there would be zero failures because you would eliminate all the options for other factors causing the failures......


Tech @ BG 09-19-2005 11:00 AM

Cam Failure
As stated by others there are way too many factors to do an accurate correlation. The majority of cams fail due to human error. You also need to look at the quality of the machine work, pushrods, valves etc... Way too many things to point the blame in any one direction.

One one hand it would make sense that there are more failures today then say 5 or 10 years ago since there are more parts coming from different areas. 5 or 10 years ago the majority of street guys were still using factory components. Now more, and more are using aftermarket components, and mixing and matching of brands. Block from one source, heads from another, parts of the valve train from who ever had the best deal, some machine work from one guy, some from another, and so on. Bottom line in a controlled environment cam failures are very small.

On the other hand it's normally flat tappet cams that fail. I would think the number of people using flat tappet cams has got to be declining with all of the standard, and hydraulic roller stuff around.

The majority of cam failures I've ever had were due to an unstable valve train. Once getting a look at it on the Spin-Tron you'd be scared of the valve train.

johnsongrass1 09-19-2005 02:18 PM


They blame it on poor quality control on lifters. According to them, lifters diameter specs have declined in recent yrs.
That happens due to human error. You didn't check the lifter bore index nor check all the lifters for proper dia.

xntrik 09-19-2005 11:21 PM

KISSing again

Mechanics and shops are trying to blame the cam or lifter manufacturers for a perceived problem that exists only in their particular state of mind.

more people are tending to routinely put stronger valve springs into their engines. Cam dynamics are improving, there is more lift with lesser duration, etc. Faster ramp rates need it, people like it for RPMs sake..... etc.

If somes good, more is better. Right?

Try breaking in the cams with "break-in" valve springs, then installing those heavy duty suckers..... it works much better in the long run. You'll be suprised how your cam failure rate drops to ZERO.

JPhil 09-20-2005 05:13 PM

Thank You
Thank you all for your replies. I appreciate your helping me to understand this, and other issues. This grasshopper has much to learn, but I am enjoying the process.

"Information alone is not knowledge, knowledge alone is not wisdom."


Jmark 09-20-2005 06:14 PM

Ok, I'll bite, what's a "spin tron"?

Tech @ BG 09-20-2005 06:26 PM


Originally Posted by Jmark
Ok, I'll bite, what's a "spin tron"?

Essentially a motorized dyno that mechanically spins over an engine. It allows you to see the movement of the valvetrain, and monitor it's movement. You can make changes to valvetrain, and measure the differences.

Super Streeter 09-20-2005 08:43 PM

There has been no change in the quality of cams or lifters in the past 40 years.All the recent cam failures are being caused by the fact that the treehuggers have forced the oil companies to remove Zinc Disphosphate from their oil.The additive had been being phased out over the past few years,but in the last year or so it has become illegal to sell oil containing Zinc Diphosphate for normal use.You can still get the correct oil for flat tappet cams by running valvoline racing oil,or by adding GM E.O.S. to the current street oils.Some mechanics have had sucess with shell deisel truck oil but this isnt a known fact.Broken in passenger car engine with higher milage wont have issue with the non zinc oil.

To put this into perspective.guys are talking about how they rebuilt their basic 350 chevy street engine with .450" lift cams and basically stock springs,and their cams are wiping out in a few thousand miles despote everything seemingly being"on the money".The same engines these guys are rebuilding ran for a hundred thousand miles or more as a daily driver before being built as high performance engines,so lifter bore alignment issues are not suspect.
Now here is the funny part,I build all my bigblock Chevy drag engines with flat tappet cams.I have found that roller lifters break too often in drag usage,and it is impossible to get 300 or 500 runs out of a set of roller lifters like I can out of a set of flat tappets{actually the rollers need to be rebuilt.replaced after every 200 runs or so even with a mild solid roller while the flat tapets seem to have an infinite lifespan}.I run nothing but stock replacement parts store lifters.In my own personal car I run a bigblock with a flat tappet cam.The block is a million mile washed out junkyard 454 block with no lifter bore indexing or bushings,just plain old lifter bores.The cam measures 310 intake 320 exhaust duration at .004,266/276 duration at .050",and .600/.620" lift at the valve with 1.7:1 rockers.I run 1.550" springs that spec at 130# at 1.900" and 510# at 1.150,but since I installed these springs after the cam was broken in{actually the engine has over 500 passes at 7500rpm on it and the old springs wore out },I put the springs in at 1.850",which puts the seat pressure at about 165#.I run 20/50 valvoline racing oil.This engine like my others has no camshaft failure issues.

With that said,you need to make note of the fact that the bigblock chevy and smallblock chevy use the same part number lifter.If this combo can support the level of punishment that I impose on it,there is no reason why "bread and butter" street engines should be wiping cams with stock springs and small amounts of lift.Take my word for it,the problem is the oil{or some other mechanical issue such as improper engine assmebly}.Dont use synthetic without EOS,but if you really want to make your cam happy,run racing oil and EOS.

Good luck.

xntrik 09-20-2005 11:17 PM

There has been no change in the quality of cams or lifters in the past 40 years.All the recent cam failures are being caused by the fact .....
.....Take my word for it,the problem is the oil{or some other mechanical issue such as improper engine assmebly}.


1) Isn't there a possiblity that there might have been some bad cam blanks or bad grindings?

2) Did anyone ever have to crank an engine for more than 2 seconds before it started the first time??? Is it possible that the continued slow cranking wiped the lube off the cam by the time it started?????

I have never seen an engine from a run-in machine lose a cam.
I have never seen an engine using break-in springs lose a cam.
OK..... 40 years.

k-star 09-21-2005 06:59 AM

Lots of good info here, I'll add some more....

1. One thing that needs considered here is the fact that 10 years ago there were fewer people using the auto message forums. So if joe cam installer lost a cam in the small town of anywhere USA he would never have known about another failure across town... Now with the internet everyone knows instantly about your cam failure...... So there is a very good chance there are no more cams going flat now then there was 10 years ago... it's just that now we all here about it!!!!! Something to think about...

2. The point about the zinc additive is a very good one and something that needs to happen. Back when i started building engines. ( the late 70's) i always used the gm EOS. Then for some reason i got away from it. I had 2 cam failures during the time i did not use it. One was 100 percent my fault, the other i blamed on lifter problems.... So i am not sure the EOS would have helped but i do know i went back to using it 4 or so years ago and have not had a flat cam since.....

3. There was a rash of bad lifters floating around... One company was bought by another and one went out of business..the one or 2 that were left had quality problems and had a boat load of bad lifters in the market... that has been resolved. So even if you do everything correct during the install and break-in if you have a lifter that has no crown on the bottom it's not going to spin and that will destroy a cam.... You can blame the cam but it was really the lifters fault...

The cam going flat deal is crazy!!!! I have seen guys with 150lb seat, crank and crank and crank engines to get them running, and then run them for 2 minutes, over heat it, flood the cylinder with fuel, run water through the pan, and on and on and never loose the cam..... There is just no easy answer to it.....


454C10 09-21-2005 08:17 AM

The EOS theory sounds interesting and I will consider that the next time I buy oil!

In the last few years I had three cams go flat on the break-in! Almost turned me off to hotrodding completely. I was considering hanging myself from my engine cherry picker! hahaha

But, I think most lobe failures that I had with my BBC's can be traced back to large clearances in the mains and rod bearing. I have since tightened up the bearings and had no problems since. Oil pressure also maintains better when warm.

0.0015 to 0.002 did the trick. 0.003 was too big!

Only use 0.003 on the rear main, 0.0015 to 0.0020 everywhere else.

Super Streeter 09-21-2005 07:42 PM

The cam going flat deal is crazy!!!! I have seen guys with 150lb seat, crank and crank and crank engines to get them running, and then run them for 2 minutes, over heat it, flood the cylinder with fuel, run water through the pan, and on and on and never loose the cam..... There is just no easy answer to it.....

I never knew you seen one of my engines run. :thumbup:

But on a serious note.I agree that there have been issue with parts over the years,but not any more so now then 30 years ago.A lot of hot rodders are totally convinced that cam companies are making flat tappet cams and lifters out of recycled Toyota scrap metal,and that there is no hope for flat tappet cams.I came up in the sport learning from a guy who has been racing since the 60's and ran and held records in both pro stock and modified production back in th early 70's.Bigblocks used to eat flat tappet cams back then too.They used to buy GM cams and have them hardened by a local metal shop.Of course back then they were running 8000 rpm 427's with stock GM 3/8 stem valves and steel retainers and 7/16" pushrods and using 200# of seat pressure to keep the thing from dropping a valve when they shifted it with their foot to the floor.He switched to a roller back around 72 or 73,but back then just like today,the roller lifters would fail and destroy the entire engine,but the lure of an extra 40 or 50 hp was too great to pass up.I think that the future of flat tappet cams is geting better in recent years.Aside from this oil problem,we have been making more power with both older and newer grinds then they were just 10 years ago.Failed roller lifters and the high cost to power ratio have been turning of the little guy racers for a few years now.Valve spring technology along with the decrease in cost of lightweight parts as technology trickles down allows for better valve control,and I see potential for reliable bigblock flat tappet cams with .700" lift or more in the future.Since the vast majority of bracket race 509 and 540 inch chevy engines with roller cams are currently running either the .714 or .708" comp or crane roller grinds,the sucess of a flat tappet of equal size would have a big effect on the preferences of most bracket engine builders.One interesting relationship I see on this front is Bill Mitchell and World products.Mitchell has always had respect for the long term durability of flat tappet cams in his race motors,and if if he really wanted to,I could see him offereing his bracket crate motors with a large ford cam bearing size and 1" diameter lifter bores,and running 550"+ bracket engines with.750"+ flat tappet cams and making gobs of power with modest rpm's and outstanding reliabilty.This would be a big hit with the big money travel road show"pro bracket racers" who want to buy 1000 hp engines that last 500 runs between valve lash adjustments and only turn 6500rpm.The potential is there,but lets see if the idea takes off.

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