Quote:
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.
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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.
Quote:
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.