Refurbished rockers?

moneymanager · 03-22-2008, 01:07 PM

Not too long ago, having found excessive scuffing on my 2.7's rockers, we replaced them during the course of a top end rebuild. I have since seen refurbished rockers for sale, but highly competent shops like Competition Engineering don't seem to do them. I assume that a rebuild would deal with bushings (if there are any,) grinding the scuffed surfaces down and rehardening. Given the price of the new item, I'd think there'd be a brisk business in these, unless there is something wrong with the idea. Thoughts? Reputable sources? Thanks.

Steve@Rennsport · 03-22-2008, 02:32 PM

Jim:

We have a company that does these for us and they have been excellent. Call me if I can help.

Its far cheaper to recondition these as they come out better than new ones due to poor machining & QC at Porsche.

moneymanager · 03-22-2008, 02:36 PM

Thanks Steve. Exactly what I wanted to know. I'll get in touch next time this issue arises.

hcoles · 03-27-2008, 06:38 AM

just what I heard - seems there always seems to be "a place" where they are sent.. I think this place has some sort of jig that grinds down the pad with the correct arc and properly aligned with the rotation axis. New bushes can be put in and honed to the proper dia. relative to the rocker shaft dimensions. I put in the new bushings and went to my machine shop and we both went through the set honing to fit the rocker shafts. The pad surfaces were "cut" by "an outside guy" this gave me new pads running on new reground cam. I think one of these "outside guys" is in Santa Clara... but I'm not sure... it seems to be some level of a secret. It seems to me that the new bushings should be done before the pad grinding...as I would expect that the pad machine references off the bushing ID. None of this may be of a big help just a bit on what I did and a few thoughts from a DIYer

aws · 03-27-2008, 11:06 AM

I have heard but not confirmed that Webcam will resurface rockers with a stellite finish. Talk to Laurie at Webcam about it. The Webcam number is 951-369-5144

aws

Jeff Alton · 03-27-2008, 02:00 PM

Camgrider on the forums here does this and does a great job.

Cheers

moneymanager · 03-27-2008, 03:35 PM

I'd think some heat treating...rehardening might be involved, and that there might be as much skill and care involved in that as there is in the grinding. Can anyone comment?

shbop · 03-27-2008, 06:25 PM

I recently went through about two dozen re-built rockers assembling a 3.0. I kept checking the contact patch between the cam lobe and rocker pad to get an even approach, and eventually ended-up getting it done by changing rockers, but slowly. Is this common to have so much difference between these parts, and how much out of alignment is considered OK?

cgarr · cgarr's Garage

shoot for at least 80% but 100% is best. "shbop" did you use new or used shafts? Used shafts can cause them to not pad well too.

911pcars · 08:23 PM

Webcam recommends new, not reground rocker arms when used with their steel billet or welded cams. Why? It could be the surface hardness. Other cam manufacturers/grinders may use a cast iron shaft which produces a different friction/wear condition between cam lobe and rocker tip materials. Any thoughts here?

I'm not sure the usual "refurbished" rockers include rehardening the tip. When this surface is reground, it's unknown how much material is removed to arrive at a clean surface. Webcam is probably suggesting another layer of caution to ensure product longevity.

Assuming PAG uses high quality steel in their rockers, according to one source, the effective hardness depth using various heat treatment processes is about .75mm max. (0.0295") After resurfacing, a thinner hardened layer remains. There's the rub (pun). With resurfaced-only rockers, the amount removed (perhaps multiple times) is unknown (to the consumer) unless the rockers have also been heat treated prior to resurfacing.

http://www.key-to-steel.com/Articles/Art113.htm

Something to think about.

Sherwood

911 tweaks · 03-28-2008, 06:14 AM

so... what is recommended and/or used on our rockers? Anyone know for sure?
Also, who does the recommended process of grinding and or hardening?
...maybe it is better to buy new rockers??????????????????
Thanks, Bob

cgarr · cgarr's Garage

The rocker faces are between 57-60 HRC (Hardness Rockwell C scale) I get no change in surface hardness when a simple facing is involved, however I have flame hardened faces when a substantial amount of material is removed, but make sure you keep the same face profile.

304065 · 04-01-2008, 02:40 PM

I sent mine to Ollies, they came back beautifully. They don't heat treat them, I asked them that and they said they never heard of such a thing, but their rockers work fine. I also had the rocker shafts polished. But I'm also using new DR camshafts made on their billets, not steel or welded lobes, so there may be a difference.

shbop · 04-01-2008, 03:13 PM

Craig,
I'm inclined to go with your theory on this. Perhaps I was being a bit overzealous in trying to get near perfect contact at each location. Once fired-up. it probably doesn't matter that much. The difference between blond and brown ones is pretty small. I like checking them when I install, but trying to get perfect contact was probably unrealistic.

cgarr · cgarr's Garage

John,

If you surface them in a coolant bath (as you should) then you really don't have to worry about flame harding them but if they get hot while surfacing, you will loose it all, take a good file and run it across the pad (should get nothing) then check the back side of the pad, (soft) its the same material but huge difference. I have some bad pitted cams here and if you check the area around the pitting the metal is completely soft. I don't know what comes first, the pitting then heat thus loosing its temper or the metal becomes soft, then pits.

Steve@Rennsport · 04-01-2008, 07:10 PM

FWIW,...many new rocker arms are not ground square from the Factory so I'd rather use refurbished ones, now.

KTL · 04-04-2008, 07:48 AM

Craig's done his share of research on this to recondition the rockers properly. Not only does he obviously know about the facing of the rockers, he's also got a "special" bushing he's testing. Great results from what i've heard so far!

Also, be aware that the wear spec on the rocker shafts is crazy small. I don't have it handy here at work but I recall it is really tight. Polishing the shafts should be done with caution to make sure you don't end up with a shaft that's too loose of a fit on the rocker bushing.

hcoles · 04-04-2008, 07:56 AM

I was also wondering how the "special" bushing project is going.. the last time I asked re. can they be honed to size or something like that ... then didn't hear much back.. that I remember. I don't think he ran them in an engine.. just on the lathe setup. I think this part of the engine is a bit of a weak spot.... probably ok when everything is perfect...
The shafts seem to get a bit of wear on them pretty easily.

KTL · 04-04-2008, 08:41 AM

I don't want to speak for Craig. But I do know he's got them in one of his engines and the bushing he's using is not something that is inappropriate for use in a rocker arm application. The bushing is designed for purposes just like this. Do a search on gruppeb.org to see what he's done.

hcoles · 04-04-2008, 11:33 AM

just checked/read - looks like there is no bad news on using this "new" type of bushing material.... I think someone was putting them in a 911 motor to test. If I read correctly the material can be honed to size to match shafts... I'm thinking this will soon become the bushings to use when opening the top end. Very cool IMHO.. when the actual in car test comes back.. hopefully we are good to go.