Interesting Rocker Discovery

[jeffnhiscars]

You could catch your finger nail on the cam lob which is why we decided it had to go and your explanation of why the rockers should be dealt with makes perfect sense.

Thanks

[digger]

Not sure what you mean. Rockers are hardened all the way through whereas cams are surfaced hardened, yet they both wear out.

should not be wear on the cam than can be felt with a finger fail otherwise it really needs to be replaced to keep the engine running as it is supposed to.

the wear pattern on the rocker arms creates some funky patterns that can result in pretty localized gouging, flatspots etc in the position when the rocker ratio is highest where as other parts of the pad are basically unaffected. This doesnt seem to happen on a cam unless its well past being toast. i think the cam "wears" more uniformly over a larger surface area so a new rocker mates up fine with an older cam provided the cam isn't worn too much but a worn rocker will more readily create wear a new cam because the wear on the rocker is more localized due to the sweep pattern.

[ForcedFirebird]

What he is getting at is, it's similar to flat tappet cams and lifters. It is recommended you replace the lifters with a new cam, but an old cam can take new lifters. Since the cam is only case hardened, once you go through that, you wipe the lobe off with the lifters (rockers) that are hardened through. These are sliding surfaces and why we should be using high zinc oil.

[jeffnhiscars]

the cam isn't supposed to be a wear surface, that's why.

Not sure what you mean. Rockers are hardened all the way through whereas cams are surfaced hardened, yet they both wear out.

[nando]

the cam isn't supposed to be a wear surface, that's why.

[jeffnhiscars]

We all agree on what the best practice is here and I think it's safe to say very rarely do we all follow those practices completely either cause we discount it, can't afford it or just don't feel like spending the time or money to make it "as new". The real question is what's the cost benefit equation as it relates to real world risk.

1) For those who have had premature wear on a new cam without replacing the rockers what was the driving style (i.e. Track, auto X, DD) and was the engine stock or "performance enhanced" ?

2) if you are supposed to replace your rockers when you replace the cam, why have I never seen anyone say you have to replace the cam when your broken timing belt takes out half your rockers and you replace those ? I mean don't new rockers with an old cam create the same wear inducing mismatch as a new cam with old rockers ? Surely someone has had half their cam lobes vaporize as a result of replacing half their rockers and leaving the old cam. No ??? Hmmmm

just food for thought...and comment.

Note...I pay $23 for a jug of M1. Dyno was $15 last I checked. Not significant

[TobyB]

That's who has done mine- Delta Cam, in Tacoma.

And yeah, spend the $13 for the additive-
I've been bitten twice now, and it's just
not worth not doing it. Or use a break-in oil- it's actually
cheaper than the M1.

t

[digger]

call a cam grinder, they should have equipment

[jeffnhiscars]

You really..REALLY need th face to be square to the bore of the rocker so as simple as this is, it has to be precise or the pad will not sit flush on the cam lobe.

I'll see if my machinist has the jig or else will find someone who does. For the $50 or so this will cost, I'm in

[Kershaw]

That doesn't look that hard to make. Put your bench grinder near your vise, 2 long bolts, a couple of washers, and a scrap piece of wood or metal with 2 holes drilled in it, and maybe you got it.

I'd definitely practice on a throwaway one first....

[jeffnhiscars]

Hah...EZPZ

https://m.youtube.com/watch?v=k5CV3pv1Bgo

And this is cool. Anyone know where to get one ?

http://www.google.com/patents/US3566550

[jeffnhiscars]

I was not aware that pads could be refurbed so will check around for a shop that does it after i check the rockers for side play on th shafts. Good info

I do use assembly lube and run Mobile 1 15-50'which has lots of zddp. I can always add some more for initial wear in if it matters.

Are you suggesting to run it at 2000 just til the oil circulates or for xx minutes to bed the cam ?

[digger]

new or refurbed pads is a must with a new cam IMO its not worth the risk of damaging the cam, many people do it i'm sure but many people don't change timing belts either.

Also running the cam in is a good idea, i dont think yo need anything special on this spec of engine its basically stock just whatever oil you current use at it should have enough zinc and so forth anyway but make sure you coat the rocker pad and cam faces with moly lube before start up and run it at 2000rpm or so to take some load off the nose of the cam and pads and get some more oil flow happening to the topend.

[TobyB]

But: if the cam wore out, then the rockers are worn in a mating pattern to the lobes.
Getting a cam to bed to the rockers has become one of the harder things with old
sliding- tappet engines now that the oil's "green" and lacks the sliding friction additives
it had when these engines were new.
Refacing seems like a good compromise- they'll bed, you'll spend $50, and life's good.
Spend for the high- ZDDP break- in oil, too- it's cheap insurance.


Honestly, too, take 10 minutes and check the springs. If they're good, you won't break a rocker.

What I'd do (what I DO do) for a dd,

t

[jeffnhiscars]

This is another one of those discussions where every comment needs to include the disclaimer that "your experience may vary". Pros and cons to every option unless you spend big bucks which I've already said I'm not going to do, just for practical reasons.

It's safe to say my OE rockers are not going to break since a)!they just don't seem to break and b) we are talking DD with auto trans (I can't repeat that often enough).

The consensus is the only downside is possible premature wearing of the new cam which I'm prepared to live for a few reasons. One is if my old cam was not past its "best by" date I'd have reused it and I can't believe the new cam won't outlast a used cam regardless of the rockers. Second, I wonder how many people who follow the new cam new rocker policy also replace all their guides, valves and springs (which I did). Third, a worn cam is a worn cam...big deal...you fix it for about what a set of rockers cost. A broken rocker has a very different outcome.

Last thought (for the moment) is whats the extent of the damage when a timing belt breaks and the rocker doesn't ?