'Splain me why I need to resurface rockers for new cams?

[Tippy]

Only reason that made sense to me is, is the rough surface traps oil to prevent galling during wear in.

Is there something I'm missing?

TIA

[Dpmulvan]

New cam and old rockers= different hardness. You want them close to same hardness so one doesn't prematurely wear the other out.

[Tippy]

Originally Posted by Dpmulvan

New cam and old rockers= different hardness. You want them close to same hardness so one doesn't prematurely wear the other out.

So you're saying after resurfacing, they are rehardened? Deeper you go, the less hard they'd be, right?

[Josh D]

Metal to metal contact parts develop a wear pattern over time. If you use a new part with an old part, the old part will cause abnormal wear on the new part, or vice versa. Two new parts, if broken in properly, will wear together and develop a "matched" wear pattern.

[Tippy]

Ah yes, that makes sense.

[Tippy]

Ok, we can close this thread. My dumb question was answered.

[Josh D]

Originally Posted by Tippy

Ok, we can close this thread. My dumb question was answered.

Not a dumb question at all. Your question may have saved someone from premature cam or rocker arm wear/failure.

[Tippy]

Originally Posted by Josh D

Not a dumb question at all. Your question may have saved someone from premature cam or rocker arm wear/failure.

Very true. Never thought of the uneven wear.

Begs me to question though, say a machine shop does the resurfacing, but their equipment isnt true. Might have been better without resurfacing?

Just a wild guess...

[gtc]

Yes. There are a few threads on here showing rockers that were not resurfaced straight, so only one side contacted the cam.

[Tippy]

Originally Posted by gtc

Yes. There are a few threads on here showing rockers that were not resurfaced straight, so only one side contacted the cam.

Right on, thanks

[bgyglfr]

This is why you need to keep track of where the rockers are when rebuilding if you plan to reuse them with the cams. The wear pattern is unique to each individual rocker/cam surface.

[RedCoupe]

Originally Posted by bgyglfr

This is why you need to keep track of where the rockers are when rebuilding if you plan to reuse them with the cams. The wear pattern is unique to each individual rocker/cam surface.

+1 on replacing rocker arms in the original places ahem reusing cam shafts. It isn't unusual for the rockers and cams to wear unevenly. If you put a rocker arm that has worn with an unusual wear pattern and put it against a re-ground or new cam, the uneven wear pattern of the rocker arm can damage the new cam before it's even broken in. Yes, we have read about poor rocker arm regrinds damaging new cams. But, just because there are some shops that have done bad rocker arm regrinds doesn't mean it's a good idea to install old untouched rocker arms with a new cam.

[afterburn 549]

I went against the grain of thought as I usually do -
I installed a new reground cam.
The old rockers - I broke out the Dremel and polishing sauce. A couple few hours later of my time they were all mirror polished on the working surfaces.
I am not advocating anyone do it this way, but I do not see what other magic could be involved at some other shop.
I sold the car with 50 K on the rebuild, never a problem with it.

[Tippy]

Originally Posted by afterburn 549

I went against the grain of thought as I usually do -
I installed a new reground cam.
The old rockers - I broke out the Dremel and polishing sauce. A couple few hours later of my time they were all mirror polished on the working surfaces.
I am not advocating anyone do it this way, but I do not see what other magic could be involved at some other shop.
I sold the car with 50 K on the rebuild, never a problem with it.

Thanks for the honesty!

[afterburn 549]

All I know everyone poo-pooed me at the time.
It worked because the engine did not ever develop an ever expanding valve lash adjustment problem.
This would be indicative of a cam lobe / lifter, rocker was wearing away .
If I ever did another engine I would do it again.

[afterburn 549]

When thinking about it , - each engine has a little different cam to rocker foot angle.
Even if you install new cams this angle will stay the same.
it would seem like there is no better choice but to make sure the rocker goes back where it came from as it has a proper angle wore to the foot.
Now if polished up all pretty, it has to be a good fit and contact.
JMO