Fighting CWC camshaft wear, VG valve springs?

[CerealWars]

What's up Datto brethren?

 

I bought a '77 280z this summer with a mystery engine in it.  The deeper I tore into it the more it seemed like someone was building a badass little l28 but gave up along the way.

 

I've been spending some serious time with her lately, trying to piece it back together properly on a microscopic budget (goddamned college, z cars are far more important).

 

I have an N42 head that's been freshly rebuilt and apparently milled (it had cam tower shims).  After discovering that I was missing lash pads, and that I had a unknown aftermarket CWC billet camshaft, I have a few questions.  After researching all I could, I discovered that CWC cams have been known to wear out quickly, except for applications used with stock valve springs, as well as a few camshafts produced by another company using the CWC billets that nitrided them.  I saw in another thread that someone mentioned using VG30 springs, saying that they were slightly stiffer than stock L-series springs.  I used to have an old z31, and still have a spare set of valve springs laying around.  Does anyone have any more experience with this?

 

Also I have both an oil spray bar as well as galleries in the cam/cam towers, not sure if additional oiling would be sufficient to keep the cam from wearing.

 

Speaking of oil, I plan on running something with a high zinc content to keep wear to a minimum.

 

Finally, and hopefully someone can chime in on this, but I was thinking of at the very least induction-hardening the camshaft.  This would be done with map gas torch, (told you I'm pretty broke).  But I don't see how that could hurt it.  This is what GM does with their differential and (manual) transmission gears to produce high surface hardness (limiting surface wear) while keeping the core of the gears ductile enough to sustain some abuse.  The cam is made of ductile iron.  Alternatively, do shops exist where I could go to to have it nitrided?

 

Alright, I know I'm killing you guys with all these words and shit, so here's some head.   ;)

 

 

Thanks to anyone who can contribute to my budget build, trying to get her on the road before spring!

[datzenmike]

Induction hardening is done with electricity. You're thinking of using a gas welder??? I'd skip that idea as doing more damage than it's worth.

[CerealWars]

Sorry Mike, should've been more clear, I meant flame induction hardening.

 

http://en.wikipedia.org/wiki/Case_hardening#Flame_and_induction_hardening

[ggzilla]

You mean flame hardening. Induction hardening uses induction heating.

[CerealWars]

When I took a material science class we studied them as the same thing (since their effects are so similar) and it was not clear to me that they were two completely separate processes. My fault, dumb mistake.

[EricJB]

I cant help you with heat treating with a torch. I have used heat treat ovens, but not for a cam. I would be concerned with warpage.

When you fire the motor for the first time, You will need to run it at 2000 to 2500 for the first 20 minutes. This 'work' hardens the cam and lifters together, while making sure it has adequate oil. I have never had a cam go flat, but know others who have. IMO too little spring pressure is worse the a bit too much. You don't want the rockers slapping the cam.

 

[CerealWars]

I agree with the break-in strategy and appreciate the suggestion on spring pressure, i never considered the effects of too little spring pressure.  Anyway, the whole cam will not be heated, just taking a $7 bottle of mapp gas or propane to the outer layer of the cam lobes, so I can't see it yielding too much distortion.  Hopefully I'll be taking the cam to my materials professor today if he has time.  The guy worked for GM for twenty years or so, and knows WAY too much about metal treating processes.

[banzai510(hainz)]

CWC us just a cast makers mark. I know Schneider and Webcamshfts cams I have (Are CWC marked)

 

My Schneider is fine I run one stock spring and one after market Nissan motorsport spring(might be a Isky spring).

Since my Schneider is 460 lift I dont havr to worry about the stock spring collapsing or stacking up.

 

key is use new rockers arms and use the correct size lash pad

 

ck the back of the cam for writting.

[datzenmike]

I cant help you with heat treating with a torch. I have used heat treat ovens, but not for a cam. I would be concerned with warpage.

When you fire the motor for the first time, You will need to run it at 2000 to 2500 for the first 20 minutes. This 'work' hardens the cam and lifters together, while making sure it has adequate oil. I have never had a cam go flat, but know others who have. IMO too little spring pressure is worse the a bit too much. You don't want the rockers slapping the cam.

Never understood the 2000rpms for the first 20 min. I doubt Nissan does this. I worked at GM years ago and did work for a day starting trucks at the end of the line roll off. Fire up and drive to the parking lot. There was never a warming up period... you drive them away. (assuming the watchers don't signal a shut off from a visible leak. One truck didn't have an oil filter on it)

 

I think this is something cam makers have you do to assure that their cam gets lots of lubricating oil. If I was running a rebuilt motor for the first time I would be much more interested in quickly getting it out on the road and start breaking the cylinders in. For just a cam swap same thing. I've replaced rockers with used ones and I've mixed them up before.... zero difference, ran fine. Lack of maintenance, (checking/setting the lash) failure to change the oil and using a fram filter, and using a cheap motor oil is more likely the cause of cam wear than a failed 'break in'. I won't loose sleep over it.

[EricJB]

So your the one that made all those cams go flat. Kidding.

 

I would imagine the rpms are for oil pressure, but work hardening does take place. Try drilling a deep hole in steel with very light pressure. let it get good and hot. Then try to push. It will be tough at first, if it moves at all.

 

It also give the cam grinder an out, when it goes flat. "You didn't break it in properly"

 

I have mixed up rockers, and lifters with no bad effects. But I try not to.

[datzenmike]

I imagine the cam lobes and the rockers (or followers) are made extremely hard and smooth to resist wear. As long as they are kept 'cool' and lubricated they should not wear. Smooth is a relative term. At some microscopic level there will be 'roughness' and the two surfaces must 'wear in together' but for the most part they are riding on a film of oil and it's the oil that either makes it last or fails, even if over many years and miles. Cams don't just wear out. Metal has to contact metal in order to scuff. It's many years of poor oil or excessive spring rate and lifts that exceeds the oil's ability to properly protect. Oils have additives like zinc to improve scuffing resistance although these days it's being slowly reduced towards being phased out. After market cams are very likely higher lift and possibly higher spring rate so they just want to ensure lots of oil on start up.

[ggzilla]

GM had vast problems with flat cams be 30,000 miles.

 

 

You can be sure Datsun prepped their's correctly.

[datsunaholic]

Factory cams were prepped right, can't say the same for aftermarket because you simply don't know.  The big issue is that the cams were made in the days of (relatively) high-zinc and low, if any, detergent in the oil.  That's fine on modern, roller-follower engines, because cam wear is negligible.  Not so good with direct-contact cam systems, like flat-tappet engines or finger-follower OHC systems.

 

 L-series engines don't really have the problem that flat-tappet engines have, which is the edge of the tappet would scrape the uphill slope of the cam.  Datsun L-series "rockers" are curved and the contact block is larger than the cam width so as long as the wipe pattern doesn't run off the contact block, everything is fine.

 

Until you run with no oil pressure.  This is where modern oil bites L-series engines.  The high detergent and "runny" characteristics of modern oils doesn't let it sit on parts like older oils, so the lack of ZDDP really is a double whammy. 

 

Modern street oils are extremely low in zinc, and have increased amounts of detergent that washes the zinc away.  The zinc-additive oil would sit on parts, retaining leaving a film that protected the parts when the engine was started (and had no oil pressure for several seconds).  That's where most of the wear happens on a street engine.

 

While diesel oil has more zinc, it also has even more detergent.  However, I use diesel oil, so we shall see.  Irregardless, I'm experiencing a lot more cam wear now than I did 5 years ago.  The flip side is the cam that basically lost a lobe is a CWC billet.  Go figure.  It was a good lopy torque monster too.  Oh well.

[datzenmike]

GM had vast problems with flat cams be 30,000 miles.

They sure did. They found that the cams were more than hard enough and so to save money they 'cheapened' them slightly to save money. There was nothing wrong with the newer cams IF you maintained the oil change interval properly. Which all GM owners did.... NOT!!!

 

GM motors had a history of being tough and so if you missed an oil change shrug so what? Catch you next time, right? Well second and third owners just drove them and they ground them away. My '82 Grand Prix was this way when I got it. Two cylinders were not working and half the others were worn down somw and lifters cupped. New RV cam and look out!!!

 

I was there in 74 before this problem, and even after I imagine they still drive them off the line right to the parking lot. Cam break in begins when you start it, nothing to worry about.

[CerealWars]

CWC us just a cast makers mark. I know Schneider and Webcamshfts cams I have (Are CWC marked)My Schneider is fine I run one stock spring and one after market Nissan motorsport spring(might be a Isky spring).Since my Schneider is 460 lift I dont have to worry about the stock spring collapsing or stacking up.key is use new rockers arms and use the correct size lash padck the back of the cam for writting.

CWC cams were a billet produced by CWC textiles in Michigan some years back. After the "Japan"-stamped cams reservoir was all dried up, CWC made tons of these and sold them to various cam vendors who ground them to be sold to the public from there. There is no writing on the back of the cam. "C2", "D2", "F13", and "EP" are the only things besides "CWC" embossed into the casting, and haven't done me any good researching my cam. After reading this thread,

http://www.zcar.com/forum/10-70-83-tech-discussion-forum/125256-cwc-cam-castings.html

and considering my un-stock looking valve springs, I'm hesitant to just throw it back together. Especially when I have VG springs laying around that just might fix the problem for essentially free.

 

Mike, I totally agree on the necessity of oil being number one priority. Anybody out there running some super secret oil that keeps the old l-series happy? I just want to put my l28 back together and not have to stress about the rockers munching the cam.

[ggzilla]

I have VG springs laying around that just might fix the problem

What problem are you having?

[CerealWars]

according to zdoctor's post in the aforementioned thread, high spring pressure is causing excessive wear rates on the cam. I've heard vg30 springs fit (and they look like they do, I've got some laying around), I was hoping for more info on this. apparently they're stiffer than stock (7k redline desired) but not by much. anybody else hear anything on this?

[banzai510(hainz)]

hopefully you dont have those franken rockers. But actually jap spec rockers. Most likely you do.

 

I dont have bad wear on my cam and soem others on here have tried Webcamshafts stuff and the Toyota LC Engeenering use CWC cast blanks

[CerealWars]

Well hey, thanks hainz. The rockers do look like pretty sturdy OEM ones. And yeah, I've heard of a few instances where in some of the top shelf camshafts they'll go to the trouble of nitriding them and those things never wear out.

[datzenmike]

according to zdoctor's post in the aforementioned thread, high spring pressure is causing excessive wear rates on the cam. I've heard vg30 springs fit (and they look like they do, I've got some laying around), I was hoping for more info on this. apparently they're stiffer than stock (7k redline desired) but not by much. anybody else hear anything on this?

.

If high spring pressure is causing excessive cam wear how is going to stiffer VG springs helping?

[ggzilla]

That was my question, especially since stock springs are good to 7000 rpm already.

[CerealWars]

I've heard that the vg30e springs are about 10 lbs/in (only a slight increase) stiffer than stock l series. Another thing I've read in a few places is that the valves start to float a little before 7000 rpm with stock springs. I don't have stock springs, but I have vg30e and vg30et springs laying around. And the aftermarket springs on it now look kind of overkill for a cam with a reputation for having soft lobes.

 

http://www.zcar.com/forum/10-70-83-tech-discussion-forum/115576-msa-cam-kit-questions.html

I found posts numbers 1 and 5-10 to be informative to my situation.

 

You guys think I should trust the mystery man who assembled this engine a few years ago and forgot to install lash pads? I'm just concerned with the way this thing was conceived when it was rebuilt. As much as I love working on engines, I don't really want to tear this thing back apart until it's time for more upgrades.

[ggzilla]

Do not trust anyone. Measure the springs and if they are within spec, use them.

[CerealWars]

Now that is probably the most trustworthy advice one could give.

[banzai510(hainz)]

LIke I said you can try a stock inner or outer and used the After market other spring.

or vise versa.

 

I think the outer strock spring will stack up before the inner close to 480 lift.

 

you need to ink pen mark the rockers then install them . set the valve lash. then tuern the cam a few times thern remove the rocker and see if the wipe pattern is in the center. Hopefully the supplied lash caps are the correct size.

 

save this

http://www.spannerfodder.com/the_works_escorts-generic-image.php?imageName=images/the_works_escorts/pinto/pinto-rocker-ratios.gif