Resurfacing rocker arms twice?
 

I have a set of rocker arms from a 2.0l. When I took it apart I saw that the rocker arms most likely have been resurfaced before, is it possible do it again?

http://img503.imageshack.us/img503/9397/car014wp8.jpg

http://img521.imageshack.us/img521/4848/car012tb9.jpg

Early 2,0 rockers have silver-solder on the rubbing face I believe. This would need to be removed and built up and then the rocker face resurfaced.

Also you may have the short 18x48 rocker shafts with the small pinch bolt vs. the later type, this is simple enough to measure.

John,

Those early steel rockers are hard-chrome faced and shouldn't be re-ground.

Steve is correct
The contact surface is hard chrome. I believe it can be replaced with a more modern process call thin-dense Chrome.

Here is a place to have your forged early rocker (both solid and adjustable) rebuilt.
The cost to recondition each arm is $45 USD and Mike Reed at "Electronic Chrome and Grind" is the preferred source for reconditioning these very rare racing parts, "Webcam" uses his services exclusively!
You can reach Mike at (562) 946-6671, they are located in Southern California at
9132 Dice Road, Santa Fe Springs, CA 90670
Website http://www.ecgrinding.com

These early rockers are well worth restoring. They are without doubt stronger and they also have a slightly better rocker ratio. 1.5:1 vs 1.45:1 if memory serves me.

Thank's for all the info...

I measured and they have the shorter rocker shafts. Can these rockers be used with the longer (later) shafts and would that be a benefit?

Steve said these rockers shouldn't be re-ground, can they then be used as they are with new cams?

Henry, the cost of recondition the is $ 45 USD each... what would I have to pay for a set of reconditioned later style rocker arms?

Sigmund,

You can buy a used set of cast-iron rockers, contact Tom1394Racing (Tom Butler)- he sold me the set I used. Ollies reconditioned them and rebushed, they are ready to go.

The trouble with the short shafts is I believe they use the smaller diameter pinch bolt.

http://forums.pelicanparts.com/uploa...1171291328.jpg

http://forums.pelicanparts.com/911-engine-rebuilding-forum/343519-rocker-shaft-pinch-bolts.html?highlight=inbus

John

Do you have an e-mail address for Ollie's?

This set on Ebay looks like a reinforced Carrera set (stronger than earlier styles) and Ed can ship them to Walt @ competition Engineering to get them properly rebuilt.

http://cgi.ebay.com/ebaymotors/Porsche-911-Rocker-Arms-Shafts_W0QQcmdZViewItemQQcategoryZ33624QQihZ005QQi temZ150260299079QQrdZ1QQsspagenameZWDVW

Walt at Competition Engineering is a great choice for all Porsche machine work.

www.competitioneng.com

Email: compeng@gte.net

$23 and change shipping for the above rockers/shafts. Hmmm. Reminds me. Sellers don't pay Ebay the amounts collected for shipping.

Sherwood

Hello P-car engine/rocker pad experts,

I found this thread after looking at the condition of my rocker pads (surface that rides on the cam).

Car: 89 3.2, rockers resurfaced at 72k miles, now 98k. Cam reground to 964 at 72k miles by cgrinder. Cam surfaces look fine. Oil BP 20-50. Rockers resurfaced at a place near San Jose CA. , I was told, it is "farmed" out. Some of the rocker pads look fine, about 1/2 of them.

Walt viewed these pictures and said it looks like surface not hard enough. I agree this is the most likley cause. I'm not second guessing Walt just wanting some more ideas and comments. I found this situation while taking all the rocker shafts out and checking sealing leaks and installing new rsr seals. This is on another thread called rocker shaft fretting. I just wanted to get more opinions that surface hardness is the issue and what to do from here. Since I have the engine out of the car I might as well resolve this if it won't last another ~ 20k miles.


The picture editing I did sort of makes things look bad, you can feel the pattern with your fingernail.

Thanks very much for additional comments.

http://forums.pelicanparts.com/uploa...1273414825.jpg



http://forums.pelicanparts.com/uploa...1273414856.jpg

Update - I found a wear pattern.
Cylinders 1,2 and 3 both intake and exhaust rocker pads have this type of wear pattern.

Cylinders 4,5 and 6 exhaust look very good, almost no visiable wear marks, 6 intake has a mild form of the "pitting" problem.

Does this mean - lubrication issue on the drivers side bank? I have the updated oil line restrictors installend and using Brad Penn 20-50.

Those rockers are forged and if you jump time, they dont break but brake everything below them.
ruce

I'm not real good at interpretation.... I take that to mean the the condition of the pads will eventually or soon mess up the cam. If you mean something else please relay it.

Here is another theory - you may recall I was one of the people who have rebuilt their engine and installed a cam 180 out and ran it for maybe 40 mins. that way. This means one side didn't heat up. A bit far fetched.

I'm thinking now of checking the tube oreintation and pulling the spray tube/etc. and checking for any blockage.

Another person just posted that some are not really in favor of the oil line restriction mod.

I think Bruce is talking about the rocker arms at the top of the page. Those are for an early car and are forged. Your rockers are cast, as all 3.2, 3.0, 2.7, 2.4, 2.2 engines have. (Unless someone retro-fitted the early forged rockers for a race motor build.)

here are a few threads to kill time :rolleyes:

I am in the "No Restrictor" camp.

http://forums.pelicanparts.com/911-engine-rebuilding-forum/446489-oil-restricrors-revisit.html

http://forums.pelicanparts.com/911-engine-rebuilding-forum/310463-cam-oil-line-restrictor-adapter.html

http://forums.pelicanparts.com/911-engine-rebuilding-forum/259165-anyone-used-oil-restrictors.html

http://forums.pelicanparts.com/911-engine-rebuilding-forum/107641-cam-tower-restrictors-good-break.html

http://forums.pelicanparts.com/911-engine-rebuilding-forum/151035-cam-oil-line-restrictors-p-ssing-me-off-they-keep-splitting-sealing-washers.html

After more thinking and reading posts regarding the root cause, this is where am at on the most likely root cause.

1 - One cam geometry is messed up causing the wear. I think this is low probability with cgrinder and I saw one rocker on the other bank with a similar issue. It was intake #6, last inline for oil.

2 - Rocker Pad Soft - this is a low probability considering the hard thickness is 0.030" and typical grinding takes off very little and it didn't happen spread across both banks.

3 - Inadequate Lubrication - I think this is the most likely cause:

a - what changed (installed oil line restrictors)
b - left bank has a "clog" in the spray bar or feeding lines/fittings
c - is it the fault of the oil? I don't think so using BP 20-50 and I live in a moderate climate
d - right bank last worse oil feed is #6 intake rocker so lubrication is likely not quite enough on the right bank either

4 - long shot - when I rebuilt I ran one bank cold (cam 180 out) and or I forgot to put asm. lube on the cam faces, 25k miles ago.

My plan at this point is to pull the spray tube on left cam tower and clean out all the lines and drill out my restrictors to 1/2 way between current and original stock. Get the rockers re ground, install everything and give it a try. Maybe inspect after 5 k miles.

"2 - Rocker Pad Soft - this is a low probability considering the hard thickness is 0.030" and typical grinding takes off very little and it didn't happen spread across both banks."

Where did you get this info? Hardness layers aren't typically this thick - more like a few thousandths.

This is a high pressure area and a high pressure break-in lube is usually called for at first start. How's the matching cam lobe? Factory cam or rewelded?

However, if this was the only rocker, perhaps excessive material was removed or, as you suspect, there might be other causes of this.

Sherwood

see notes above

My error. It seems 0.030" (~8mm) is on the upper end of for case hardened materials. However, would still like to confirm that's the depth for rocker arms.

Thanks,
Sherwood

When I get home tonight I will have to sacrifice a good rocker and put one to the test and post what I find here. I will take one down until I loose it.

cgarr,
Very kind of you to sacrifice a rocker and provide solid general info. for the group but may not be completely necessary on my account. Cgrinder mentioned that typically not much is ground off to resurface a rocker but I don't recall he mentioned an amount, I'm guessing 0.005" or less. On some thread there must be the hardness depth on a stock cam lobe, this has been discussed on threads here and there is an adequate amount to cut out a 964 profile with increased lift. That's my reasoning to guess the thickness is well over a few mills. Thanks much for doing an experiment.
-h

I don't believe the cast rockers are hardened as we do rebuild these here in-house and have not found this to be the case. We do regrind each rocker pad to get a fresh, parallel and properly curved surface as SOP.

I will say that hardwelded cams are much harder than the rocker surfaces and its imperative that the cams are coated with a moly lube made for camshaft break-in, not general assembly lube. Further, the engine MUST be run at 2000 RPM for the first 15 minutes to break in newly refinished cams and rockers. In some cases, we hard-chrome the cast rockers for improved durability with welded and reground cams.

Naturally, one assumes the spray bars are all clean and not obstructed in any way. I do not use nor recommend the cam restrictors as the use of those are counterintuitive to me. These are highly loaded areas of the engine and require lots of lubrication as well as cooling.

Hi Steve,
you may remember I've been to your shop years ago now. The rockers are 3.2 89 vintage. I may be guilty of taking over this old thread that had another type of rocker discussed initially.
I'm fairly quickly coming to the conclusion that lack of lube is the most likely root cause and I'm considering going back to original restrictors or "split the difference" restrictors. Yes I'm going to check my spray bar, looks like I need learn the pulling the bar out insitu process. It makes sense that the cam ramp line contact hit on the rocker pad heal could be one of the highest stressed points in the engine. That's the exact area of the wear pattern. We need roller rockers :-)

Here is a rocker I ground out .040 and took off .030 and it still maintained its original hardness, however I would not use one that had that much taken off, they get a bit thin.

http://i30.photobucket.com/albums/c3...1/100_8534.jpg
http://i30.photobucket.com/albums/c3...1/100_8536.jpg
http://i30.photobucket.com/albums/c3...1/100_8537.jpg

Craig,

you took 0.040" off to start with and then an additional 0.030" per the pictures you posted and the material was still hard.... curious how you measured the hardness, do you have one of those Rockwell diamond stylus machines? I haven't run one of those since college days. There are likely many other ways to get hardness that I'm not familiar with. I think you can even use a file and get a good idea. Excellent work, this means there is a lot of meat to work with.

Even if you confirmed there was only 0.030" that would be a good amount to work with for a couple of 0.005" passes.

Thanks,
-Henry

Hi Henry,

Indeed, I do remember,...:) :)

I would recommend the original "restrictors" (lack thereof) as these are highly stressed parts even with the modest valve spring rates.

Roller rockers would be ideal but unfortunately, there is not sufficient room. Several good people have tried to do this, but unless the cam towers are totally redesigned, its not feasible.

I am assuming that hard chrome has an extra step added to avoid potential problems due to plating such as hydrogen embrittlement from the acids used. Could you please provide a little education for me on the subject? Thanks :)

I don't know the details of the process since the gent who does this regards this as proprietary, however its been VERY durable for me.

I believe its a similiar process that Porsche used with the early forged steel rockers. :) I still have several sets running in several cars and those have been in service since they were made. :)

Max,
The acid used in hard chrome plating is sulfuric acid in the 0.13-0.23 oz/gal (1-1.73 g/l) range, part of the bath containing the chromic acid or chromium trioxide (CrO3) to create the hexavalent chromium, a carcinogen but not really an acid (referred to as a hypothetical acid). This is a very weak acidic solution. For comparison, battery acid is about 33% strength in the 1.25 Kg/L range (or 1000 times stronger). I would not be too concerned about hydrogen embriddlement when acid in this concentration range is used also because the entire part is not plated as is the case for fasteners.

I imagine the hard chrome is used for the same reason that it is used in the barrels of many firearms, the .45 ACP and the M-14/M1-A come to mind. In the weapons, it is not practical to lubricate the barrel between shots and the hard chrome reduces pitting and fretting as the bullets pass through the barrel at high temperature and high speed.

The hard chrome is just that - a very hard surface that will resist the fretting caused by the impact vibration of the cam lobe against the rocker. Quality lubrication will just about prevent the fretting seen in the pictures elsewhere in this thread. However, a combination of high temperatures (thin oil), high RPM (increased surface speeds), and tight clearances, high lifts, or heavy valve springs will contribute to the problem of fretting (the hard particles that break away and then are immediately crushed into the softer surface, the rocker face).

Mark

I would imagine that the early forged rockers would be hardened and tempered to a reasonable level to ensure that they are tough and have good resistance to fatigue. The section of the rocker is reasonably cosnsistent and I would expect that the hardness would be consistent throughout the section.

The only real way to be sure would be to cut across the section and use a Vickers Hardness tester and measure every 0.5mm. A Rockwell machine is not really suitable for this type of work.

The hard chrome plated onto the wear surface does have microsopic 'pits' in the surface which help it to retain an oil film which when combined with the basic hardness of the chrome give a good wear resistant coating.

I can see no reason why this layer cannot be removed by grinding and then have the part re-chromed. Modern Hard Chroming techniques are much better than those used in the ealry Sixties and should give excellent results.

Companies such as Poeton can now Hard Chrome in a well controlled manner and hard chrome many components so accurately that tthey don't need to final grind.

The hydrogen embrittlement that occure during hard chroming is a result of a 'Hydrogen Overvoltage' in the electrolytic cell causing 'atomic' hydrogen to be generated at the materials surface.

It is conventional to oven bake susceptible parts at around 250degC immmediately on removal from the cell.

If I were to recondition forged rockers I would grind of all the chromium, shot peen the wear face and the re-chrome.

Whether or not this is worth the expense is another arguement.

The investment cast rockers are unlikely to be surface hardened. I am sure that they will be made from a stell that can be hardened and tempered which is why they will have a consistent through hardness. I would imagine it is possible to reclaim this type of rocker by hard chroming but the expense is unlikely to be justifiable.

I think if I were to remanufacture rockers now I would use a good quality steel forging such as 4340AQ and then finish the wear pad with a modern material such as DLC.

Excellent information. :)

What is the mechanism which causes atomic hydrogen to make the metal more brittle? Is it due to its greater electronegativity (along the lines of carbon) causing it to steal electrons from the metal without forming a covalent crystal lattice to strengthen/stiffen it in the way carbon does?

How does the baking get rid of it? Just by making the hydrogen more energetic so it goes quicker to a gas phase and forms H2 molecules?

I guess I could have wiki'd first. :rolleyes:

Hydrogen embrittlement - Wikipedia, the free encyclopedia