Cam Wear?

[grannyknot]

I don't mind,    I love oil wars, we haven't had a good oil thread in a while.

 

Not sure what it is about oil that makes people so passionate but it does lend itself to

heated discussion. I love some good back and forth.

Edited April 17, 2015 by grannyknot

[Captain Obvious]

Oh yeah? Well my oil is better than your oil.

 

edited it just so I could have the little banner come up like you did. My edit is better than your edit.

Edited April 18, 2015 by Captain Obvious

[grannyknot]

Thank you Blue!

Philip, very kindly just sent me 3 Nissan rockers so I can replace that bad one.

You are a scholar and a gentleman.

[siteunseen]

He's a scholar for sure, and I'm sure a nice gentleman.  

 

Blue's fan club senior member, Cliff. 

 

scholar

 

[skol-er] 

Spell Syllables

• Synonyms
• Examples
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noun

1.

a learned or erudite person, especially one who has profound knowledge of a particular subject.

[240260280z]

I hope you are lucky like Dr 240z and I were.

 

I did the old-school non-detergent 30wt correct break in on a new Delta reground set of rockers, Delta cam, correct new lash pads and new Crane springs and retainers with lots of break-in grease and great oil flow before first fire up. 30wt was again used at 50miles with a new filter. Mobile 1 oil synthetic was used after 500mi. The cam was eaten ~ 1,500mi.

 

2nd try was a new Schneider cam and new reground Delta rockers with ZDDP oil treatment.  One rocker started to fail but it looked like a manufacturing flaw like Grannyknot's.  Swapping in a refreshed rocker did the trick.

 

From this experience I think the metallurgy, quality of the machining, spring pressure, and the oil additives are all important for correct break in and long life.

[djwarner]

Ok, I suddenly have a dog in this fight. While finishing up my bottom end overhaul, it is time to do a serious inspection of the cylinder head. It had been overhauled around 30,000 miles and 12 years ago and was pulling very good compression and idle vacuum, so I wasn't expecting to find anything serious.

 

I found 3 of 4 cams on cylinders 4 and 5 as bad or slightly worse than Grannyknot's If anything, two of them had a single gall stripe in the center deep enough to penetrate the case hardening.

 

The last time I adjusted the valves, I failed to adequately torque the screws on the spray bar and they loosen after about 500 miles. I heard the shrieking as the cams ran dry, but I was about 15 miles from home when it happened. I limped home but didn't see anything this bad when I inspected it. I've put about 3,000 miles on the engine since then. 

 

Anticipating I might run into problems, I purchased a used but very serviceable cam from Madkaw thinking I could slip it in while the engine was torn down. But something I read in Tom Monroe's "How To Rebuild Your Nissan & Datsun OHC Engine" has given me pause. 

 

On page 87 Tom writes, "When checking the cam and rockers, check the cam first. If it's bad, you'll have to replace the cam and rockers, regardless of the rocker-arm condition. Remember the second rule: Never install used rockers on a new cam." (Italics are Tom's, Bold emphasis is mine.)

 

Obviously, this contradicts what several posters have said in this thread.

 

Of course I don't have a set of rocker-arms. Nor do I have the expertise to determine what lash pads to use if I did change them. I can tell you that the current cam profile is OEM and not a regrind.

 

Other than this issue, the overhaul has gone smoothly considering the last overhaul I've done was 53 years ago. The crank was surprising clean, smooth, and to size during it first overhaul despite the 186,000 miles on the clock. Cylinder bores had minimal enlargement and no taper to speak of. Bearings were worn in the appropriate places down to the copper.

 

So here I am ready to put the head on and install new timing chain hardware once I sort out the cam issue. What say ye?

 

Also the gasket kits I purchased came with some Orings about 1.25" in diameter and I can't figure out where it is supposed to go. Any clues here as well?

[siteunseen]

The cam from Madkaw is a stock used cam, right?  I think it would be fine with your stock rockers if they're not galled from the spray bar failure.  You could do what Blue has done with a piece of marble and some sandpaper but that would require removing them.  Post some pictures if you can.

 

I remember an O-ring around the distributor shaft.  I put one under my oil cap too.

[240260280z]

There is a right way to do a job and there are adequate ways to do a job.

 

 

Replacing with new rockers is the right way.  Using refreshed rockers is adequate in most instances (as done and documented by many) but it depends on the metal type & hardness, shapes of metal, oiling, and skill & judgement of the installer..... and, as always, some luck.

Edited April 22, 2015 by Blue

[Chickenman]

It's your tone.  Needs work.  And too much verbiage to make a simple point.  So no, after seeing the tone, then all of the words, I didn't read all of your posts.  I tuned out and moved on.

It's very hard to judge Tone via the Internet. I think you've made too harsh of a judgment on me and vica versa.

 

It's just the way I prefer to write from previous experiences on technical discussions in other Forums. I find it more efficient to make a statement, and then support that statement with as many facts as I can. Like a " Shot Gun " effect. Short statements and explanations tend to lead to multiple posts explaining the original concept. That's all. Lets move on... agreed?

Edited April 22, 2015 by Chickenman

[Chickenman]

(Snip)

 

Also the gasket kits I purchased came with some Orings about 1.25" in diameter and I can't figure out where it is supposed to go. Any clues here as well?

If rubber/nitrile, probably the O-Ring that seals the distributor to the adapter housing.

 

Edit: Just noticed " Siteunseen " beat me to it...

Edited April 23, 2015 by Chickenman