[darbikrash]

Originally Posted by 1968GTO421

".When you nitride a cast iron cam, the process reduces the core hardness of the material. You end up with a very hard, but thin outer layer, but the backing material is now much softer. The hard shell. helps with break-in, but the after a while the softer backing material gives way, and the hard shell starts to flake off. As soon as that starts, your cam is toast."

I’ve read this numerous times on Speedtalk and it’s always from the same guy- a cam grinder- who ought to know better.

A properly nitrided cam, meaning of the correct case depth and hardness for the contact stresses anticipated will not suffer an adhesion failure due to a “soft core”. Plasma (or Ion) nitriding was designed specifically to withstand high impact loads, and it was originally developed for use in hot forging dies which receive hundreds of tons of impact force and do not suffer abnormal wear or any delamination after years of service.

Regarding the combination of DLC lifters and nitrided cams, the general rule about running hardened surfaces against each other is that they should not be at or near the same hardness, but rather at least 6-9 Rockwell C difference, and the more the better.

Typically nitriding a cam gives you 58-63 Rc, DLC is much higher, close to 100 Rc.

[grivera]

There was a YT video posted a few months back where numerous cams were tested for hardness and IIRC the conclusion was the failures are lack of a ramp on line or other machining issues. Seems if that isn’t addressed a DLC coated lifter would destroy a nitrided cam in short order. 64Speed’s machinist spent time making sure all lifters rotated and that the cam was machined properly to lower risk of a failure.

[Formulajones]

When I'm building a flat tappet cam engine, the cam gets nitrided. On top of that I'll use a lifter that lubes the lobes right on the face. Been doing that for a while now. In fact I've been daily driving one like that for 6 years now and it's been perfect, some 60,000 miles later. So for the average car guy here that might drive 1000 miles a year, that'll probably last a life time.

[darbikrash]

I stopped by the Comp booth at Sema this week and talked to some technical folks about Comp's lifter program. One of the guys was pretty familiar with the DLC testing program and he said the plan was for Comp to offer the DLC option on all vehicle makes for (flat tappet) lifters going forward. Pontiac is scheduled for "sometime next year" with SBF up next for the upgrade. SBC and BBC are available now. Current pricing is +$20 per set (16 lifters) to get the DLC coating.

In the pic below you can see they are coating only the lifter face, not the body of the lifter.

The fellow I spoke with said they had done extensive Spintron testing on coated lifters and could not force a failure even with abusive testing. According to him, the coating does not wear off after break in and is not sensitive to oil additives.

I asked about combining a Nitrided cam with DLC coated lifters and he said they had done no testing on this but should increase durability even more, but in his view was unneccesary as the DLC was enough.

All Comp lifters are now made in Michigan, with coating outsourced to another division of Edelbrock/Comp also in Michigan.

He said that in Spintron testing the greatest cause of premature lifter failure with uncoated lifters was excessive coil spring bind height of the spring- #1 killer.

On the roller lifter front the Evolution roller cartridge program has been very successful (according to him) and going forward all Comp roller lifters will migrate to this technology, replacing the existing roller design.

Time will tell, but it looks to me like Comp has taken the lifter failure issue seriously and put in place some good upgrades.

The main point I got from all this is that the DLC coating of inexpensive flat tappet lifters (when available for Pontiac) gives everyone that doesn't need large valve lift numbers a really good option away from the expensive roller cam setup.

[ponjohn]

Originally Posted by Dragncar

I have some BAM SR lifters with a DLC coating on the pin/rollers contact surface.
Have not used them yet but the reputation is they are very durable.

I don't see Pontiac rollers on the Bam website, are they customer order?

[grivera]

This is the video I referred to above, based on the results of this testing the quality of the machining is more of a factor - the short of it is hardness is not the issue with any of those in the sample.

https://youtu.be/DMFikj-TAqo

[1968GTO421]

Member geeteeohguy has said regularly here that the machining on the base of the lifter and the taper on the camshaft's lobes are the problem and has been for several years now. I get the feeling that if I found a camshaft ground prior to year 2000 that would be optimal.

[1968GTO421]

Member geeteeohguy has said regularly here that the machining on the base of the lifter and the taper on the camshaft's lobes are the problem and has been for several years now. I get the feeling that if I found a camshaft ground prior to year 2000 that would be optimal.

It would be interesting if there was a site where folks who had camshaft/lifter failure could list the camshaft grinder who made the cam and we we could see if certain manufacturers were worse or better in this regard. FWIW

[Shiny]

Originally Posted by darbikrash

I stopped by the Comp booth at Sema this week and talked to some technical folks about Comp's lifter program. One of the guys was pretty familiar with the DLC testing program and he said the plan was for Comp to offer the DLC option on all vehicle makes for (flat tappet) lifters going forward. Pontiac is scheduled for "sometime next year" with SBF up next for the upgrade. SBC and BBC are available now. Current pricing is +$20 per set (16 lifters) to get the DLC coating.

In the pic below you can see they are coating only the lifter face, not the body of the lifter.

The fellow I spoke with said they had done extensive Spintron testing on coated lifters and could not force a failure even with abusive testing. According to him, the coating does not wear off after break in and is not sensitive to oil additives.

I asked about combining a Nitrided cam with DLC coated lifters and he said they had done no testing on this but should increase durability even more, but in his view was unneccesary as the DLC was enough.

All Comp lifters are now made in Michigan, with coating outsourced to another division of Edelbrock/Comp also in Michigan.

He said that in Spintron testing the greatest cause of premature lifter failure with uncoated lifters was excessive coil spring bind height of the spring- #1 killer.

On the roller lifter front the Evolution roller cartridge program has been very successful (according to him) and going forward all Comp roller lifters will migrate to this technology, replacing the existing roller design.

Time will tell, but it looks to me like Comp has taken the lifter failure issue seriously and put in place some good upgrades.

The main point I got from all this is that the DLC coating of inexpensive flat tappet lifters (when available for Pontiac) gives everyone that doesn't need large valve lift numbers a really good option away from the expensive roller cam setup.

Good info, thanks for the post. Great to see them bringing this to the market and I hope it pans out for everyone.

It would be interesting to know if the testing was capable of finding a problem without the DLC coating. As I understand, a Spintron can be used to replicate the behavior of a valve-train in an engine. To me, this means the test evaluates a "system" (cam, springs, pushrods, lifters, etc.) so to discriminate, I think you'd need to either "test to failure" or have a way of comparing wear on the lifter.

I wonder if Comp will publish their test results?

Basically, I'm curious if they could force a failure on non-coated lifters and if so, what were the specifics. Can they nail down finishes, geometry, loads, lubricants, etc. that lead to failure? Not hard to believe coil bind would cause excessive loads but that sounds outside the typical application.

Originally Posted by grivera

This is the video I referred to above, based on the results of this testing the quality of the machining is more of a factor - the short of it is hardness is not the issue with any of those in the sample.

https://youtu.be/DMFikj-TAqo

Yes the video makes an argument but I don't think you can extrapolate to DLC. A typical hardness test uses an indenter that penetrates quite a bit. DLC coatings are so thin, would they even affect a typical hardness test? I suspect the indenter would just crush right through it. Yes, DLC is very hard, but because it's so thin, I'm not sure the hardness is its most important property for lifter wear. I'm just guessing, but expect DLC has a low coefficient of friction that might reduce adhesive wear.

[darbikrash]

As it was explained to me they did run A-B comparisons of coated and non coated lifters on the Spintron. During the “abusive testing” phase several extreme conditions were tested. One test condition was excessive spring length above coil bind. During this test the uncoated lifters showed significant failures, while the DLC coated lifters showed no failures. Over the various test conditions, this was the #1 source of lifter failure meaning that more uncoated lifters failed here than any other test condition.

This effect is often called spring surge. To give an example, installed height specs for a spring might call for a minimum of .050” above coil bind, and a maximum of 0.100” above. The “abusive test” would have a number much larger than the 0.100 maximum, say for example 0.300”. It is fairly common to have builders exceed the max number, because “more is better, etc.”.

This causes harmful ocillations in the spring which (when multiplied through the rocker arm ratio) transmit percussive forces directly to the lifter face. You can find high speed videos online showing this, but basically this creates a jackhammer effect and tears up the lifters.

This is not an explanation for why every flat tappet cam in the world has failed. It is a conclusion of a very specific test which has some useful conclusions

I believe the way to think about DLC coating is to consider it as an insurance policy, if (and when) something goes wrong in the valve train, the coating can provide substantial protection and possibly avoid a catastrophic failure. There is no one saying the cams or lifters are too soft, and for sure coating a dimensionally flawed lifter after the fact does no good.

Originally Posted by Shiny

Yes the video makes an argument but I don't think you can extrapolate to DLC. A typical hardness test uses an indenter that penetrates quite a bit. DLC coatings are so thin, would they even affect a typical hardness test? I suspect the indenter would just crush right through it. .

Yes, 100% right, DLC is around 10 microns thick, way too too thin to measure using standard Rockwell testers, which are designed for materials that are through hardened. Even case hardened parts (like cams) can be a problem if the case depth is too shallow.

[Shiny]

Thank you darbikrash!

It seems that the tests identified at least one system with high risk for failure and was able to discriminate well enough to show DLC could mitigate.

This is excellent.

Thanks for straightening out my misinterpretation. I now understand the finding of "too much" margin above coil bind leading to dynamic instability. This is probably not a surprise to most but as you say, the dynamic loading and effect on lifter wear is probably not as high on anyone's radar as just losing control of the timing events.

Clearly the big list of factors that contribute to lifter wear performance makes it hard to compare something as seemingly basic as a lifter brand comparison or a DLC coating.

I personally would happily pay $20 for a coating known to reduce failure risk under at least one set of variables.

I think it's awesome to find a supplier investing the level of testing you describe in today's world of supply chain nonsense. Your post has definitely left a good impression of Comp!

Thanks again for sharing this.

Mike

[Dragncar]

Originally Posted by ponjohn

I don't see Pontiac rollers on the Bam website, are they customer order?

https://vincentperformance.com/shop/bam-b-2030-16-bb1/

[TransAm 474]

Any other/new thoughts on the Comp Cams DLC lifters? We just bought a set to try in a 383 Small Block we are building .... gonna be used along with the Lunati VooDoo "704" camshaft

[Jay S]

For an extra $20 it is certainly an easy choice to add the DLC. My opinion has not really changed, I think that DLC is really helpful on the break in. The tech mentioning durability testing done with Spinatron testing is pretty cool. I don’t know what percentage of failures occur from the types of testing comp did on their spinatron with spring surge issues. But my guess for something on the street the percentage would be pretty low.

Personally I think most failures are because the machining on the lifter taper and or cam isn’t done very well. Plus there is some softer metal out there also, I have heard of some cams dropping down into the upper 20s on some Rockwell tests in recent years. Either way, if cam breaks in and too much of the taper is removed on the break in, and life of the cam is shortened up, and often doesn’t make it past the break in right now. The DLC on the face should really help the break in, Nitiriding the cam makes the break in go a lot smoother too. Pair up it would be better yet. It is also not unusual to get a couple tickers with hi energy lifters, especially with aggressive cams. In that regard the DLC on those hi energy lifters is a bit like lipstick on a pig. You may get to return a couple lifters to get all the blead rates the same. I have never been around a hi energy lifter that didn’t have a ticker with Voodoo’s and XE cams. Maybe it is just my luck though. But I think the DLC is a good start at the issues, hat’s off to comp for moving that forward.

[Lee]

Originally Posted by joes455

Now I can install my summit $90.00 2802 cam with a set of $800 lifters

Do you already have that cam? If not, it is now $158, and will likely be more expensive in a few months.

If you look at Summit Racing, most of the available CompCam HFTs are $270-286 now.

[i82much]

Hopefully they will have this available for Pontiac solid flats whenever I blow up my hydraulic roller.

[Formulajones]

lol

[i82much]

Originally Posted by Formulajones

lol

i mean really ... right now i have OF 1.0, rev limiter at 5500 rpm. 1.5 rockers. Very safe, it will probably live forever ...

but there is a part of me that wants to put a snotty 290b6 in there, think about it ... 505 cubic inches ... extra wide ratio muncie ... 3.54 gears ... just rip it up to 6500 rpm every time i drive it ...

but would i really just be giving up power in exchange for a top end that could rev higher?

[Formulajones]

Originally Posted by i82much

i mean really ... right now i have OF 1.0, rev limiter at 5500 rpm. 1.5 rockers. Very safe, it will probably live forever ...

but there is a part of me that wants to put a snotty 290b6 in there, think about it ... 505 cubic inches ... extra wide ratio muncie ... 3.54 gears ... just rip it up to 6500 rpm every time i drive it ...

but would i really just be giving up power in exchange for a top end that could rev higher?

LOL I wouldn't worry about it. I've been buzzing my hydraulic roller in my 454 to 6500 for 25 years, hasn't broke yet

Dad can't seem to keep his 571 off the rev limiter (set at 6200) with his hydraulic roller.

They'll rpm and last forever if built right with good parts. Saving weight is key. My BBC as an example are probably one of the worst when it comes to that. But here it is living just fine.

In fact we are working on a little 327 right now that'll zing pretty good with a hydraulic roller. Much lighter drivetrain parts and a good set of Johnson lifters and the cam that Paul is choosing should make peak up around 6500 or so.

[i82much]

Originally Posted by Formulajones

LOL I wouldn't worry about it. I've been buzzing my hydraulic roller in my 454 to 6500 for 25 years, hasn't broke yet

Dad can't seem to keep his 571 off the rev limiter (set at 6200) with his hydraulic roller.

They'll rpm and last forever if built right with good parts. Saving weight is key. My BBC as an example are probably one of the worst when it comes to that. But here it is living just fine.

In fact we are working on a little 327 right now that'll zing pretty good with a hydraulic roller. Much lighter drivetrain parts and a good set of Johnson lifters and the cam that Paul is choosing should make peak up around 6500 or so.

I change my mind like every other day about what to do with my car. One day I want a procharger, the next day I want mud flaps and snow tires so I can drive it all winter.

It's a lot easier and cheaper to post about what you're gonna do on the internet than it is to actually get off your ass and do it