Rocker arm wear, oiling issue?

[JT68]

Long winded, but certainly useful. My recommendations were just based on my previous and latest experiences, no scientific testing.

I have not tried many of those oils in the blog, and generally don't need or use any of the additives that are touted, but if we assume its all accurate ( I have no reason to assume otherwise), it can still possibly help out Greg.

Greg suggest you find the oil you have used on the list and pick a mix with at least 25-50% higher loading rating. To be scientifically valid you'd have to run the same parts, the same length of time, same operating conditions. But I realize your intent is not to test motor oil LOL.

Other suggestions would totally invalidate the oil test conditions, but might help you:

a. Bite the bullet and use 4 new rockers. I'm not a fan of reground for several reasons, but they often work OK. "New" insures the correct hardness and surface finish IF Nissan kept their QC intact from whatever suppliers they used. (major assumption)--of course "new" could change the wipe to depending on what you originally set up.

b. try a different cam. (perhaps stock or B) The ramp profile makes a BIG difference in wear characteristics. Race cams can be brutal on the whole valve train.

Also remember that what works for an L series or other engines often doesn't work for U20. (They are similar but not the same) - careful with expert advice from "L-series guys"! j

[msampsel]

Yes Greg, try a stock cam ...
That will fly

And no offense intended on your recommendation JT.

[GeoffM]

Greg, how's your oil pump?
And as an aside,( just to throw another variable into the mix) gear pumps produce more flow with thicker fluids. There is less internal recirculation. This holds true even well above the viscosity of grease.

[Gregs672000]

Again, appreciate all the info and thoughts! I'll know better once things are back together and I can do some testing. On an aside, Steve and I have been discussing some rocker arm options. For some time he has been telling me about some material he has come across that could allow us to modify, replace and/or weld up two or even one piece rocker pad surfaces. When the full process is complete, the hardness is "Rockford 60" if I'm hearing his words right, but in essence is bullet proof. If it works out, we could produce high quality rockers, and even make that pile of one piece ones useful again (I personally have 16 of them). I'll keep you posted.
This is not a radical cam... I don't have the specs at hand but it is an Isky z-197.

[JT68]

Rockwell. Rc60. Thats about the same a stock (depending). Common hardness for tool steel.

Since i already make hardened tool steel lashpads, As you might imagine, I've looked into this as well.

With new rockers at 50$, the economics don't work to try to rebuild a rocker with a new pad.

Unless its specifically a result of regrinding, I don't think this is the fault of the rocker wear surface.

That's considerably more cam than you may have thought. .5" lift is working everything much more than you realize.

I know your engine runs better with the cam timing corrected, but it may run even better with a little less cam.

The oil pumps usually hold up well so if yours has less than 50k on it, doubt it is the pump.

If you really want to keep that cam, you might build a spray bar. (Bit of a PIA)....could be as simple as better oil though, but with that much cam, recurring wear may be a problem without special lubrication/steps. That seems to be what is going on.

[JT68]

Since there are multiple potential causes here, and we are just guessing at this point, suggest you just try the simplest first. Fix the cam, new rockers and upgrade to a more exotic oil from the test list, (10w40 is fine). Stay with that oil going forward, don't deviate. I doubt it will be worse than before and may cure the problem...(again, I'm assuming your oil pump is low miles)

Also, I wasn't specifically suggesting a stock A cam necessarily. Even a C cam isn't lifting at .500 so either a B or C might be easier on the valvetrain than the Isky. The ramp design on the Nissan profiles is very different from an ISKY.

I think Stan and Mike Young might have some C cams on hand if you wanted to tinker with that for fun, or I can get one ground for you.

Anyway, if it was me, I'd try some very, very high grade oil in 30 or 40 weight for the next 10k miles and see what you find. JMHO

Camstand journals still look perfect? (if so it probably isn't starving for oil)

J

[Gregs672000]

I'll verify the cam specs, pretty sure I have the cam card in a box somewhere (moved a while ago and some things are still boxed up). Not sure the listed z-197 is the same as what I have. I can also have Delta profile it and give specs too. We talked for quite a while about this engine, compression, head work, valve size, spring rates etc and this was what he thought would work best. This was in relation to the specs on other cams I had run though, and those cams probably suffered from the same cam timing issues this one did prior to the adjustable gear. Sooooo, I'll get specs, compare them to the cams I currently have (B grind, Racer Brown grind) and see what I decide to run. So far though, the Isky has been great, once timed better.

[spyder]

I had a Z-196 cam go south on me which was re-ground by Isky. What added insult to injury was it was an original B cam.
They said send it back. I did along with an A cam for a re-grind. I assumed they wanted to look at the failed cam. However, they re-re-grounded it for me along with the A cam.

Back when I had a cheap camera!

[Gregs672000]

Thanks Spyder. The Z-196 is the bigger cam that I was avoiding for my car for the street with the gearing I have (4.11). Lift is .530 and duration is 306 (264 at .050), vs what is listed for the Z-197 08 (Porsche version anyway, maybe that is the "08"?) of .499 lift and 278 (246 at .050) duration. The wear on my cam is similar but not as bad... looks almost like material from the rocker transferred to the cam on mine. What did your rockers look like? Like I said, the back 3 rockers were perfect and they clearly got oil earlier than the others. I also see your cam was damaged at #8 rocker... were they all bad?
After you had it reground, any continued problems? I know you still run this cam so I assume not...

As I said, I do have a B cam and a Racer Brown grind (I'll have to check the cam for which one, it is written on it)... B cam is .460 lift, 280 duration (not assumed to be a .050), C cam is .480 lift 296 duration (again, not at .050) per Dean's site.
So, if Spyder can successfully run a cam with .530 lift, should be no reason why I cannot run a .500 lift I would think... In addition, my valves are probably lighter unless he's running 7mm stems (pretty sure mine were 7mm, might be 8mm but not stock for sure), stock springs (checked for bind, well able to control the lighter valves and should be sufficient to keep them from floating). As I am reading, a high lift cam with shorter duration is a bit harder on the valve train, but the lower duration keeps the cam in a lower power band (though lift contributes too). Not sure how the wear characteristics of the Z-197 compares to the Z-196 Spyder is running given the different specs.

JT, I do see you noted that the ramp profile has an impact on wear. I really want to run the Isky as it has been great, but again I'm not comparing apples to apples because of the cam timing issue. However, I do like the lift and duration for the Isky, at least on paper, as it would seem to slot into the power band etc that I am looking for given compression, head flow, valve size etc.

[spyder]

The follower showed no sign of damage.

[Gregs672000]

The follower showed no sign of damage.

Wow, interesting. No problems since?

[JT68]

That's why I wasn't quick to blame the rocker arms unless it is because they were reground. The 2piece rockers have been run hard with success in too many engines. The metallurgy between the cam/ rockers is quite good. It can be difficult to replicate. (Nissan had more than one mis-step as did other manufacturers)

"So, if Spyder can successfully run a cam with .530 lift, should be no reason why I cannot run a .500 lift I would think... "

Have to be careful here.There aren't too many conclusions that can be drawn from from Spyder's experience that are directly applicable to Greg's. There are just too many variables all which could directly create the observed outcome.

If the engines were identical that would be different, but here's a short list of differences between the two engines that could easily create the problem:

Different rate springs
Different nose pressure
Different seat pressure
possible float
Different ramp profile between the two cams
Different duration (affects the previous)
New or reground rockers
Different wipe
Different Break-in procedure/conditions/lubrication
Different oil
Different oil change frequency
Different peak oil pressure
Different relief valve pressure
Different surface finish on the rockers
Different valve weight
Different installed height (affects geometry and many of the above)
...
..

Swapping cam and rockers experimentally changes many variables at once, so it might be fun, but I understand if you want to try to sort it out with the Isky// j

[Gregs672000]

True that JT! By the way, I found my racer brown cam... 341-R. Only specs I could find so far is .500 lift, 242 duration at .050. Virtually the same cam specs as the Isky. I've read other partial specs on sites saying lift is more like .480, so if anyone knows let me know. I can probably ask Delta Cam too, as they ground it as I recall.
No doubt, I'm sure the rockers are getting tired. May be time to invest in a new set.

[SLOroadster]

I've been running the same bigger cam than you have since 2006, with the same reground rockers that when in when the head was built. I've had zero issues. No odd wear on either the cam or the rocker arms. I have to think it might be either and oiling issue or something to do with the oil itself. I ran Mobile 1 15/50 for years, but changed to Lubro Moly 10/60 6 or so years ago. I wonder if your rocker arm geometry is off just enough to cause the wear?

I'd be careful about running super hard rockers. If they are too much different from the cam hardness, you run the risk of chewing up the cam. (Some guys I know ran into that with their Rolls Royce Griffon at Reno a few years ago. The carbide tipped rockers destroyed the cams in about 8 hrs worth of run time. They were told by the guy who did the rockers that they would last forever and end their issues with rocker damage. Well, he was right about one thing, the rockers lasted great right till they ate the cams and were removed. )

Will

[Gregs672000]

Yep, a lot of possibilities and variables here. However, as I am sure many can relate to, the first thing to do is to go with the most obvious and simple cause. In this case, poor oil flow to those rockers. I've never had an issue before I discovered the cam was plugged earlier and I cleaned it out. Same geometry, same oil pump, same use of reground rockers. The rockers are wiping on the center of the pad and are not running off either end. I think they just did not get oil flow as quickly as they should and in sufficient quantity. Once they start wearing, it is a rapid process from there. Metallurgy is always a concern, and Steve has seen that plenty and is aware of metal qualities and variables etc in order for them to work well together.
The good news is that I have a couple of cams to work with and good access to an expert machinist and a cam grinder. One other consideration is to recheck for coil bind. I checked it when I first installed the cam, but I also run my lash tighter and who knows, maybe I'm on the edge... never hurts to check.
Thanks guys!